MX2009014163A - Ecological treatment to treat wastewaters using an enzymatic anaerobic reactor and process. - Google Patents

Abstract

The ecological system for treating wastewater includes three steps: a pre-treating stage, a second stage of enzymatic anaerobic reaction and finally a post-treatment stage, the post-treatment including a desanding element, a double grid, and a sump. The second stage also called primary treatment includes one or a plurality of enzymatic anaerobic reactors in cascade or in series of ascendant flow and finally the post-treatment is constituted by: a hydrated limestone filter, a volcanic rock filter and a swamp, a system for collecting metabolic elements based on aquatic lily and an emitter. Said combination of stages allows the enzymatic anaerobic reactors of ascendant flow to remove from about 75% to about 85% of the pollutants present in the water, which substantially reduces the post-treatment area. The pre-treatment stage includes separating and collecting sludges and rubbish such as plastics, branches, sand and the like; the primary treatment includes the removal of the highest part of organic matter that is present and dissolved in the water (carbon), the post-treatment process including aeration and elimination of nitrogen, phosphorus and potassium, and finally, the incorporation of the aquatic lily providing an efficiency of 90% in the elimination of polluting particles, which helps to reincorporate the water so that it can be used again.

Description

Ecological Wastewater Treatment System using an Enzymatic Anaerobic Reactor and process FIELD OF THE INVENTION For a long time human settlements have produced solid and liquid waste as a daily part of their daily activities - solid waste is mainly made up of garbage and liquids, wastewater, or black water; These are essentially the community's drinking water supply after it has been contaminated or fouled in a variety of uses. From the point of view of the emission sources, wastewater can be defined as a combination of liquid waste and those transported by water leaving homes, businesses and industries, together with groundwater, surface water or rainwater. In any of these modalities; When these sewage are accumulated or confined, the decomposition of the organic matter they contain leads to the production of large amounts of putrefied matter. Additionally, untreated wastewater generally contains a large quantity of pathogenic microorganisms, or disease vectors, microorganisms that reside within the digestive system of the human being or that are present in certain industrial waste waters. Wastewater contains nutrients, which can stimulate the growth of aquatic plants; they can also carry toxic compounds. For these reasons, the immediate and effective disposal of the wastewater at its point of generation, followed by its treatment and final disposal, is not only desirable but necessary for the welfare of the community and its environment.

OBJECT OF THE INVENTION The main objective of wastewater management is the protection of the environment and public health in accordance with the economic, social and political conditions of the community. In recent years there has been some confusion in Mexico between the decontamination of water bodies and public and private investment in treatment plants. Spending on the construction of wastewater treatment plants will not necessarily have an impact on the environmental problem, especially if the plant is not operated and maintained properly. Failures in the design often make the operation of the built plants impossible, the personnel is sometimes not adequate, or does not receive the training from the experts. Nowadays few human settlements have treatment plants, even so, there are fewer that perform an adequate treatment of the wastewater they produce. Currently, the treatment of all wastewater before discharge to surface or groundwater is regulated by law in environmental regulations.

BACKGROUND Nowadays, the pollution problems in the water receiving bodies have been diversified caused by the discharges of wastewater from the population centers, which have increased in such a way that it is impossible to ignore them, since the clean and available water has decreased at its levels alarmingly. Problems such as deforestation, land use change and erosion exacerbate this situation. On the other hand, the implementation of state-of-the-art technologies has resulted mostly in high cost and low performance, in such a way that some plants are inoperative. The interest in treating wastewater is based on the protection of the environment and the health of the population since, in spite of the economic, social and political conditions of the communities, this is affected by the results of the contamination, which over the years will make it more difficult and expensive to undertake emerging mitigation programs, since untreated wastewater contains numerous pathogenic microorganisms that serve as a means for the development of other disease-causing vectors and as a consequence, a population Sick, it is a population that does not produce but generates more poverty. For this reason, the immediate and effective disposal of domestic wastewater at its point of origin and its treatment and final disposal is not only desirable, but also necessary for the well-being of all.

The use of enzymes dates back several centuries and is part of cells or crude extracts of plant, animal and microbial materials. All this is supported in an empirical way, without knowing its mode of action, nor the reason for its enzymatic catalytic activity in the fermentation industry such as beer, wine, bread and cheese. Even a useful enzyme produced by a bacterium, a yeast or a piece of tissue is often used, without even extracting it from the cells. For example, acetobacter acetyl can serve to oxidize alcohol and convert it into acetic acid without first purifying the alcohol oxidase. The yeast ferments the sugar and converts it into alcohol without the extraction of the zymose complex; The many other enzymes that the yeast contains do not hinder the reaction, because they have other specific activities.

DESCRIPTION OF THE FIGURES Figure 1 shows the three stages of treatment: the pretreatment unit (upt), the anaerobic enzyme reactor (rae) and the post-treatment unit or cienega.

Figure 2 shows a flow chart of the process described in each stage of the system.

With reference to said figures the waste water (1) enters the system and passes first through an unraveling device (3) and a pretreatment unit (5), later passing through a grid (4) that will retain the large solid waste subsequently the flow entering the anaerobic enzymatic reactor (2) the gases emitted pass to a tank (7), then passes through a series of filters (6) where the separation of solids (10) is carried out to vent in a marsh (8) to the last stage of treatment for later by means of an emitter (9) to return it for its use.

DETAILED DESCRIPTION OF THE INVENTION Table 1 shows the maximum permissible limits for basic pollutants. Table 2 shows domestic wastewater pollutants Table 3 shows in summary the analysis of the technological alternatives developed above.

Table 1 SOLIDS SUSPENDED THESE CAN CAUSE DEPOSITS OF SLUDGE AND ANAEROBIAL CONDITIONS WHEN WASTE WATER ARE DISCHARGED WITHOUT TREATMENT TO AQUATIC ECOSYSTEMS.

BIODEGRADABLE ORGANIC THESE, MEASURED IN TERMS OF BOD AND COD, CAN CAUSE OXYGEN BREAKDOWN BY LEADING TO THE DEVELOPMENT OF SEPTIC CONDITIONS, AFFECTING THE ECOSYSTEM OF THE WATER BODIES IN WHICH THEY ARE DISCHARGED.

PATHOGENS CONTAGIOUS DISEASES CAN BE TRANSMITTED BY PATHOGENS PRESENT IN WASTEWATER.

Table 2 Table 3 According to the type of wastewater treatment methods can be classified and grouped to provide primary, secondary or advanced treatment. The primary treatment uses physical operations such as grids, separators and sedimentation to remove floating and settleable solids from the water. In the secondary treatment, biological and chemical processes are used to remove most of the organic matter. In advanced treatment, additional processes are used to remove specific contaminants, such as nitrogen and phosphorus, that have not been significantly reduced by secondary treatment. In this regard, it is worth mentioning that the treatment processes through the application of wastewater in infiltration fields, or in natural systems, produce a water quality similar or better than that achieved by the advanced treatment, since these work efficiently with quantities less than 500 ppm. Knowing the origin and characteristics of the wastewater that will be treated is the first step in the planning process of a wastewater treatment plant and the official regulations established to discharge the water to the body in question or issuer; Discharges of domestic wastewater are regulated by the general law of ecological balance and protection of the environment and the federal law of water rights.

The general law of ecological equilibrium stipulates in Chapter III of Article 117-IV that "wastewater of urban origin must be treated prior to discharge into rivers, basins, vessels, marine waters, and other deposits or streams of water, including the waters of the subsoil ". The federal water rights law stipulates official regulations for the discharge of wastewater. Article 277-i defines the wastewater for which the discharge rights will have to be paid, indicating that the total amount of discharged water will be paid, if the taxpayer does not separate other types of water from the residuals. While the art. 278-b establishes the following parameters indicated in Table 1 as maximum permissible pollutants.

Components of the flow of domestic sewage The components that constitute the wastewater flow of a community depend on the type of collection system used and may include the following: Domestic water: water discharged from residences, shops, offices, houses and similar places.

Industrial wastewater: wastewater in which industrial waste from factories and workshops predominate.

Infiltration / influx: water that enters the sewer system through direct and indirect means. Infiltration is water that enters the sewer system through leaking joints, cracks, broken pipe or porous walls. Inflow is rainwater that enters the system in different ways.

Rainwater: rain runoff.

For the areas currently served with drainage systems, the flow levels are determined by historical data available, as well as data obtained from measurements made directly. For new human settlements the flow is determined by an analysis of population data and the projected amounts of water consumption per capita in similar communities.

For this case, the daily flow of wastewater has been calculated based on per capita consumption and number of inhabitants, which are described in the following point (1.3.) 1. 3. - characteristics of domestic wastewater.

An understanding of the nature of domestic wastewater is essential in the design and operation of collection, treatment and final disposal systems. Its characteristics can be divided into three categories: physical, chemical and biological. 1. 3.1. - physical characteristics: Total solids - in analytical terms they are defined as all the solids that remain after evaporating water at 35 ° c. Total solids are divided into settleable solids, and suspended solids. Sedimentable solids are all that sediment in an imhoff cone in a period of 60 minutes. Suspended solids are those that remain suspended in the water after one hour of sedimentation, this sector can be separated into filterable solids and non-filterable solids.

Odors - Odors in domestic wastewater are caused by gases produced by the decomposition of organic matter and other substances in water. Fresh sewage (or residual) has a different smell, something unpleasant, but less ugly than that of water that has entered the anaerobic decomposition process. The most characteristic smell of sewage Septic or stagnant is that of hydrogen sulfide, which is produced by microorganisms that degrade sulfur. The importance of odors at low concentrations in human terms is mainly related to the stress they produce and not to the damage they cause to the body. Offensive odors can cause loss of appetite, decreased water intake, inhibited breathing, nausea, vomiting and mental disturbances. In extreme cases, offensive odors cause the deterioration of personal and communal pride, interfere with interpersonal relationships, and lower the socio-economic status of those affected.

Temperature - the temperature of wastewater is generally a little higher than that of drinking water. Temperature is very important because it determines the rates of decomposition in chemical reactions and biological processes. In addition, oxygen is less soluble in warm water than in cold water.

Color - the color of the wastewater varies according to its state of decomposition. When fresh, they are usually brown or gray. However when going through the collection system they turn dark gray and finally black. Black sewage is described as septic. 1. 3.2. - Chemical characteristics: Organic matter - the amount of organic matter present in a water sample is expressed in terms of biological oxygen demand (dbo) or chemical oxygen demand (dqo). These are the analyzes by which the amount of organic matter dissolved in a water sample is determined. The difference between these two techniques is that the dbo is made by microorganisms and will only "detect" the fraction of organic matter one hundred percent biodegradable, that is, the fraction that can be used as food by microorganisms in water. While the dqo, is determined by chemical oxidants, results in the total organic matter present in the sample regardless of whether they are biodegradable or not. Normally for pollution hundred percent biodegradable the ratio dqo: dbo is two to one (2: 1).

Dissolved oxygen (od) - oxygen is necessary for the respiration of aerobic microorganisms, as well as for other forms of aerobic life. However, oxygen is poorly soluble in water. The precise amount of oxygen (and other gases too) that are present in a solution is determined by: to) . -the solubility of the gas; b) .- the partial pressure of the gas in the atmosphere; c) -the temperature, and d) .- the purity (salinity, suspended solids, etc.) of the water.

Because reactions that take up oxygen increase with an increase in temperature, dissolved oxygen levels tend to be more critical in the summer; This problem is aggravated by lowering the flows of streams and rivers during the dry season. In some way, the presence of dissolved oxygen in wastewater is desirable because it prevents the formation of offensive odors.

Nitrogen and phosphorus - the elements nitrogen and phosphorus are important for the growth of algae and plants, are known as nutrients. Due to problems of growth of algae and aquatic plants in surface waters, there is much interest in controlling the amount of these elements in discharged wastewater.

Ph - this is a way to measure acidity or alkalinity of water. Most life forms can survive in a pH range between 6.5 and 7.5. Ph below 6.5 are acids and, above 7.5, are alkaline. The type of pollution that carries the wastewater as well as the degree of decomposition of the contaminants can change the pH of the water. Domestic sewage tends to be alkaline due to the soaps and detergents they carry.

Gases - different gases present in the atmosphere are present in the waste water, the level of dilution of these gases, as in the specific case of oxygen, determine in part the state of the water. Other gases are produced in the process of decomposition of organic matter dissolved in water, the presence of these gases and their concentration can be perceived by the smell of water. 1. 3.3. - biological characteristics: Animals - depending on the degree of contamination, different species of animals can inhabit wastewater, fish and amphibians such as frogs and toads among others.

Plants - algae as well as larger plants can inhabit the wastewater, their presence can contribute to the removal of nutrients from these waters.

Bacteria and viruses - many different types of microorganisms inhabit wastewater, the vast majority of these are not harmful to humans. The pathogenic organisms found in domestic wastewater are contributed by people infected or carrying a disease. Pathogenic bacteria excreted by people generally cause gastrointestinal diseases such as typhoid, paratyphoid, dysentery, diarrhea and cholera. Because these organisms are highly infectious, they are responsible for thousands of deaths each year in areas with poor sanitary conditions, especially in the tropics.

Because the numbers of pathogenic organisms present in waste and contaminated water are few and difficult to isolate and identify, the coliform organism, which is more numerous and easier to detect, is commonly occupied as an indicator organism. The intestinal tract of man contains innumerable bacteria known as coliforms. Each person discharges between 100 and 400 billion coliform organisms per day, in addition to other types of bacteria. Then, the presence of coliform organisms is taken as an indicator that pathogenic organisms may also be present, and the absence of coliform organisms is taken as an indicator that water is free of organisms that cause disease.

Therefore, domestic wastewater pollutants can be classified into three general categories (table 2).

Primary treatment In general, all treatment systems must be preceded by a grille that prevents large solids from entering the system and a sand trap that removes the sand that could sulphure the plant and cause wear problems in mechanical parts (in case there are ).

The grid is the first part of every treatment plant, it is considered a primary treatment, in other cases as pre-treatment. The removed solids may include stones, branches, leaves, papers, plastics and rags. These materials must be removed from the grid periodically to ensure adequate flow.

A sand trap removes dirt, sand and small stones after the grid is also considered a primary treatment. It is very important to remove these materials before they enter the plant, because they will reduce the active volume of the system as it accumulates.

It is surprising to note that in many wastewater treatment plants built in Mexico these two essential elements are missing. There is no type of treatment plant that is not adversely affected by the entry of mineral solids, sand and gravel. It should also be noted that these two primary treatments have a low cost and are very simple to install; its maintenance requires only periodic cleaning.

Secondary treatment Septic tanks.- The installation of tanks or septic tanks are a common solution to solve the problem of wastewater in rural homes or small communities. In cases where the domestic unit is too small to accommodate a septic tank, or the soils are inadequate, small communities or groups of houses can share a common septic tank by connecting all through a drainage system.

A septic tank is a prefabricated or constructed tank that serves as a combined tank of sedimentation and flotation, with partial anaerobic digestion of the sludge. Septic tanks began to be used since the middle of the last century. Today most septic tanks are prefabricated, made of concrete, fiberglass or ferrocement. Before the residual water enters the tank, it must pass through a grid that prevents the passage of large solids that could clog it. This grid should be cleaned periodically. The wastewater inlet is on the left side at the top of the tank. The tank is divided into two compartments by a wall, the compartments are connected by a tube located at a medium height that crosses the dividing wall. When the wastewater reaches the first compartment, the sludge sediments and fats and oils float.

A conventional two-compartment septic tank.

In a septic tank, the settleable solids form a layer of mud at the bottom of the tank. Fats and other floating materials rise to the surface where a cream is formed. The sedimented and skimmed water flows from the relatively clear layer of water in the middle to an infiltration field. The organic matter that accumulates in the bottom of the tank is transformed through anaerobic decomposition to more stable compounds and gases.

Although the volume of sludge in the tank will be constantly reduced through anaerobic digestion, it will be necessary to periodically empty the accumulated sludge and cream. The frequency needed will depend on the design parameters of the tank, and if it is being occupied at more or less its capacity. In general terms, the pumping and disposal of sludge from the tanks should be considered every year.

Traditional septic tank system with filtration field.

The disposition and final treatment of septic tank effluent is achieved more frequently through sub-surface soil absorption systems. Typically this system consists of a series of shallow ditches partially filled with gravel. The effluent from the septic tank is applied to the field of infiltration by gravity through perforated pipes buried in the gravel of the ditches The advantages of septic tanks are that they can reduce the cost of disposing domestic sewage from homes that are far away from the drainage system. Under optimal operating conditions, they do not produce bad odors or require maintenance or specialized operation.

Section of a typical drain of a filtration field.

There are also several obvious disadvantages in the installation and use of septic tanks for the disposal of domestic wastewater. First, they are only suitable for small amounts of wastewater; For more than 20 houses it is better to think of some other type of treatment. Second, it is necessary to empty the accumulated sludge periodically, this means a cost of removing the sludge and facilities for its final disposal. These muds can be applied to green areas, but they have a characteristic offensive odor. They should not be applied to crops for human consumption because they can often contain heavy and / or compliant metals. Another disadvantage is that the drainage field occupies space and under certain soil conditions are not suitable. The Drainage fields can develop odors and clog if the septic tank is not working as it should or if it is filled with sludge and not properly emptied.

The septic tank is the most common type of treatment found. Unfortunately, many of these tanks are for subdivisions of more than 20 houses, and most do not have drainage fields, since they are built within the city where the land is scarce.

Although septic tanks offer a viable alternative for isolated rural dwellings or small communities of 20 houses, they require an open area for the installation of the drainage field and have the need to empty the sludge periodically, which implies relatively high operating costs for Large systems, therefore, are not an alternative treatment for urban and rural areas.

Stabilization lagoons: Stabilization ponds are large, shallow and generally rectangular lagoons with a constant water inlet and outlet. The biological treatment that occurs in the stabilization lagoons is a completely natural process achieved mainly by bacteria and microalgae. The process proceeds without the intervention of the human being who only provides sufficient space and time.

There are three different types of stabilization lagoons commonly used: anaerobic lagoons, facultative lagoons and maturation lagoons.

The anaerobic lagoons, as the name indicates, do not contain dissolved oxygen and do not contain algae. While the facultative and maturation lagoons contain large populations of algae, which play a fundamental role in the stabilization of organic pollutants; therefore, they are sometimes referred to as natural or photosynthetic lagoons. The three main types of lagoons are generally located in series, with a facultative lagoon followed by one or more maturation lagoons; or an anaerobic lagoon followed by a facultative lagoon, and one or more maturation lagoons. These series are important because they allow each type of pond to carry out its different functions in the treatment of wastewater to produce an effluent of the desired quality.

Anaerobic lagoons are recommended for the treatment of heavily polluted waters, that is, with a high organic load (more than 300 dbo / l) or waters with high sediment solids contents. Anaerobic and facultative lagoons are designed primarily for the removal of organic compounds generally expressed in terms of dbo. The maturation ponds are designed mainly for the removal of pathogens (indicated by the presence of fecal coliforms) and plant nutrients (nitrogen and phosphorus); however, the removal of pathogens and nutrients are also carried out to some extent in anaerobic and facultative lagoons; while the removal of organic compounds occurs in the maturation lagoons. Stabilization ponds are the simplest type of treatment; the wastewater enters and flows through a series of lagoons by means of gravity, after several weeks a highly decontaminated effluent leaves the lagoons; however, its microbial ecology is much more complex than that of an activated sludge reactor and a sprinkler filter, and to date it is not completely understood. Below is a brief description of the different types of gaps.

Anaerobic lagoons: The anaerobic lagoons receive a daily organic load so high that the dissolved oxygen is completely absent. They basically work like open septic tanks. In fact in very small treatment systems, septic tanks frequently take the place of anaerobic lagoons. The settleable solids in the raw wastewater sediment and form a layer of sludge that are digested anaerobically at temperatures above 15 ° c.

The total removal of the dbo is high, varying from 40% at 10 ° c, up to 60% at 20 ° c. Many times a cream is formed on the surface, which does not necessarily have to be removed, but it can cause problems in some places due to the breeding of flies and mosquitoes. If it creates problems, they can be remedied by spraying clean water, or with final effluent to break the cream. In exceptional cases (such as in places where there is a danger of dengue hemorrhagic fever) biodegradable insecticides or biological control of mosquito larvae can be implemented.

The production of bad odors is considered the main disadvantage of the anaerobic lagoons, however, the odor can be controlled by ensuring that the organic load of the lagoon does not exceed the design parameters. The anaerobic lagoons are sometimes dark purple or red. This color is due to the presence of a bacterium that contributes to the reduction of the production of odors.

The anaerobic lagoons generally have a depth of 2 to 5 meters. The depth of a particular lagoon can minimize the land requirements and construction costs (the construction cost usually increases with greater depth).

Optional lagoons.

In facultative lagoons that receive raw wastewater there are two main mechanisms for the removal of dbo: - the sedimentation and subsequent anaerobic digestion of settleable solids, up to 30% of the dbo are transformed into methane gas, which is emitted by the lagoon. - the aerobic oxidation of non-settleable organic compounds together with the soluble products of anaerobic digestion. The oxygen necessary for these processes comes partly from the atmospheric oxygen, but mainly from the algae present in the lagoon, which give it a dark green color.

In secondary facultative lagoons, those that receive wastewater after an anaerobic lagoon, the first of these mechanisms does not occur. The removal of dbo in the two types of facultative lagoons is from 60 to 80%.

The depth of facultative lagoons is generally 1.5 m, although depths between 1 and 2 m are used. Depths of less than 0.9 m are not recommended because they can grow plants in the lagoon creating a habitat suitable for breeding mosquitoes.

Maturation lagoons.

A series of maturation ponds receive the effluent from the facultative lagoons. The size and number of maturation ponds are governed mainly by the water quality at the desired bacterial level in the final effluent. Depths of up to 3 m have been used, but depths equal to those of facultative lagoons are the most common.

The main parameters that determine the removal of faecal bacteria are temperature, retention time and organic load. The removal rate increases with higher temperatures and retention times, and decreases with higher organic loads.

Maintenance of stabilization lagoons.

The maintenance requirements of the stabilization ponds are very simple but must be met regularly. If they are not maintained properly there will be serious problems of odors and problems with the breeding of flies and mosquitoes. For this reason it is important to clearly define from the very conception of the project the maintenance requirements and the responsibilities in the operation, to prevent problems later. The maintenance requirements are the following: - the removal of solids and sand from the entrance grid. - the chapeo of grass and plants on the banks of the lagoons and their elimination so that they do not fall into them. - the removal of cream and floating plants from the surface of the lagoons. - the spray of cream that is formed in anaerobic lagoons, as necessary, with clean water or water from the final effluent. - the removal of any solid that may accumulate in the entrances and exits. - the repair of damages caused to the banks of the lagoons by rodents, rabbits or other animals. - repair of fences and external doors.

The anaerobic lagoons require to be emptied and cleaned approximately every 2.5 years, the frequency required can vary significantly. The sludge is usually emptied through a pump that transports it from the bottom of the lagoon to a sludge lagoon or to a pipe that transports it in turn to a sludge treatment center.

Design parameters.

Communities larger than 1,000 inhabitants should design their lagoons according to specific measurements of organic flows and loads, but for communities under 1,000 inhabitants, the size of the lagoons can be calculated using the following general formula: At = 100 p / t Where: at the total area of the lagoons in m2 P the taxpaying population t the average temperature for a population of 2,000 inhabitants, at an average temperature of 22 ° c, the result is as follows: 100 (2000/22) = 9,092 m2 (almost one hectare) These equations assume an organic load of 100 g. Per m3 per day in the anaerobic lagoon. The depth of the anaerobic lagoon should be 3 m. And that of the facultative and maturation lagoons should be 1.5 m.

The lagoons must be located at least 200 meters away from the predominant winds of the community and also away from areas of probable population expansion. This is mainly to discourage people from visiting the lagoons, but it also serves to reduce community fears about odor problems.

A) .- There must be vehicular access to the lagoons.

B) .- To minimize construction costs it is convenient that the land has a slight slope, and that the soil is c) .- impermeable. In permeable soils the lagoons have to be sealed, which increases their construction cost.

D) .- The advantages of stabilization ponds are that they have a relatively low construction cost and require low cost maintenance.

E) .- The disadvantages are that they require a lot of ground and can cause unpleasant odors. They are generally not suitable for rugged areas or regions where porous soils predominate.

F) .- When installing a single treatment plant, the sanitary sewer should be separated from the pluvial throughout the city, this in order to reduce the volume and area of the lagoons.

G) .- the oxidation lagoons are not appropriate for colonies or subdivisions within the city because they require a lot of land and produce bad odors Imhoff tanks: The removal of settleable solids and their anaerobic digestion in an imhoff tank is similar to that of a septic tank. The difference is that the imhoff tank consists of a two-story tank within which the sedimentation is carried out in the upper part and the digestion of settleable solids is carried out in the lower behavior. The gas produced in the decomposition process of the sludge escapes through the vents. Imhoff tanks can be square or rectangular.

A tube that rises from the bottom of the tank is used to discharge the accumulated sludge in the lower chamber, the frequency of discharge of sludge is determined by the design and load of the tank, generally varies between 3 months and 6 months.

The imhoff tank can separate the settleable solids with a relatively high flow and does not require more maintenance than the periodic cleaning of its inlet grid, and the periodic discharge of sludge. The organic load removal efficiency of an imhoff tank is approximately 25 to 30%, the average retention time is 4 hours. It is advisable to occupy an imhoff tank as a primary treatment, followed by secondary treatments The main disadvantage of the imhoff tanks is that they produce a lot of mud. Of a tank designed for 500 people of 60 m3, the production of sludge would be approximately 200 m3 per year. In an imhoff tank of 600 m3, designed for approximately 5,000 people, they produce 2,000 m3 of sludge per year.

Although imhoff tanks are considered obsolete since 1970 in developed countries, here in Mexico they are still being built. These tanks have been discontinued in developed countries due to the high production of sludge, which, due to increasingly stringent legislation on their disposal, requires their own treatment plant. Another disadvantage that they present is their low efficiency in the removal of contaminants, new technologies in the field of wastewater treatment offer greater efficiency eliminating the need to have several secondary treatments.

In Mexico, the accumulation of sludge is not a problem, particularly in the rural area where small population centers are surrounded by coffee, sugar cane or cocoa fields, for example. It is not the most modern technology but it is a highly studied and proven technology. Although the removal efficiency of contaminants will hardly exceed 40%; however, this result is better than that of a treatment plant of another type that is not operated, or that is not built.

Sprinkler filters: The first sprinkler filter was installed in England in 1893. Modern sprinkler filters consist of a bed of some highly permeable medium, to which microorganisms adhere, through which the wastewater is percolated by means of a spray system, there comes the name. The medium that supports the microorganisms can be of stones between 25 and 100 mm. In diameter, the volcanic stone is very suitable. The depth of the stone bed varies according to the specific design, generally between 0.9 and 2.5 m, with an average of 1.8 m. The wastewater is distributed over the bed of stones by means of a rotating distributor, the water is percolated through the bed and collected in drains in the bottom of the filter. This system of drains also allows oxygen access to the bottom of the filter.

The organic matter present in the wastewater is degraded or digested by a population of microorganisms adhered to the filter medium, the organic matter of the liquid is absorbed by the layer of lama (biofilm); in the upper part of the filter the organic matter is degraded by aerobic microorganisms, while in the lower part, anaerobic processes generally develop.

By increasing the thickness of the biofilm, it detaches from the filter medium and is carried away by the water. The effluent from the spray filter contains the treated wastewater and the biological solids that have been detached from the filter media. This liquid passes to a sedimentation tank that separates the solids from the treated water.

The biological community in the filter includes aerobic, anaerobic and facultative bacteria, these are the predominant microorganisms. Fungi, algae and protozoa are also present, as well as larger animals such as worms, insect larvae and snails.

The main disadvantages of sprinkler filters are that they require constant organic flows and loads to function properly. They can also produce problems of bad odors and the breeding of flies and mosquitoes.

Although there are several plants of this type in the country, it is not considered the most appropriate alternative, because the flows and organic loads of the wastewater change significantly during the course of the day. Another problem they have is the breeding of mosquitoes; Due to the presence of hemorrhagic dengue in the region a mosquito breeding focus is more than a nuisance, but it becomes a threat to public health. Spray filters can not be sprayed with insecticides because they would kill the biofilm responsible for the removal of contaminants. Generally the sprinkler filters are preceded by a primary treatment, a settler and must be followed by a clarifier and a tertiary treatment. The clarifier and the imhoff tank produce sludge that must also be treated before being applied to agricultural crops and / or green areas.

Anaerobic reactors: There is a wide variety of anaerobic reactors. Anaerobic digestion is a biological treatment process that takes place in the absence of oxygen. In the process of anaerobic digestion, most pollutants are converted to methane gas, a useful by-product.

The anaerobic process produces few slimes and these are quite stable, in fact the anaerobic process is the most common used for the processing of sludge from sedimentation and aerobic processes. We will describe here two types of anaerobic reactors.

Uasb: This process is known by its acronym in English, upflow anaerobio sludge blanket. The reactor is inoculated with active anaerobic sludge in the bottom. The wastewater is introduced into the bottom of the reactor and flows upwards through the sludge bed composed of clusters or particles of biological formation. The gases produced under anaerobic conditions (mainly methane and carbon dioxide) create an internal circulation, which helps the formation and maintenance of biological particles. Part of the produced gas adheres to the particles and together they rise towards the top of the reactor. The particles, when rising, impact against the degassing device, the impact causes the release of gas from the particle, which falls back to the sludge bed. The uasb reactors require retention times between 4 and 12 hours and provide between 75 and 85% removal of the dqo.

Anaerobic filters: The anaerobic filter is a column filled with one of several solid media. They are used for the removal of organic matter from wastewater. The wastewater flows upwards through the column, coming into contact with the medium to which the anaerobic bacteria are attached. The process allows for short retention periods. For this reason the anaerobic filter is commonly occupied for the treatment of diluted wastewater and at room temperature. This system has proven to be one of the most effective, as it is capable of withstanding abrupt changes in water concentration and volumetric shocks; avoiding the drag of the bacteria. A clear disadvantage is that it occupies a lot of volume and its construction costs are high.

Reactors plug flow.

A good part of the anaerobic digesters built in the country are of the "plug flow" type, with variances only in the size and location of the reactor (underground or surface), as well as the presence or absence of pretreatment. Many of these digesters have been built by the same company and all were designed by the same person. "Plug flow" refers to the way the particles pass through the tank. In this case they enter, pass through the tank, and come out in the same sequence, they do not mix. The particles retain their identity and remain inside the tank for a period equivalent to the theoretical retention period. This type of flow can be approximated in long tanks with a high long-wide ratio to minimize or prevent longitudinal dispersion. Other anaerobic full-mix reactors have shown better efficiencies under specific conditions.

Enzymatic anaerobic reactor (RAE) The rae is a semi-packaged reactor that combines the characteristics and advantages of two of the most applied anaerobic digestion processes currently: the mud mantle and the anaerobic filter. For 20 years a reactor has been developed which has been successfully applied to wastewater with high contents of organic matter. However, this design has been improved by adding the hydrolase enzyme at the start of the reactor, which now also has 3 main parts: lower part, in the shape of a cone for the retention of sludge, the middle part or cylindrical body where it is contained the water resulting from the digestion mixed with gas and the top part or domed head, which contains most of the gas generated and which is subsequently sent to the biogas receiver Bell tank.

Wastewater enters the upper part of the reactor where it is dispersed to the lower part by a series of tubes that conduct it and make contact with the anaerobic sludge bed. The organic matter they contain is digested. These waters flow upwards into the reactor, in the course of their digestion. Inside the reactor, in the last third part, there is a grate that supports a stone packing (tezontle). The water when hitting with the stone bed initiates a change of phase, the sludge is sedimented again, and the gas produced goes to the collection system, while the treated water leaves the reactor to two filters the first of quicklime, the second of tezontle and finally to a lagoon profusely planted with vegetation associated with natural marshes.

The anaerobic enzymatic reactor (rae), which works with a load of hydrolyzing enzymes that are a function of the organic load, are of vegetable origin, which act in the process of digestion accelerating its activity and reaction time. It has the ability to remove between 70-80% of the organic contaminants from the wastewater. The effluent from the reactor is practically decontaminated but has the characteristic smell of anaerobic decomposition. To eliminate this odor and remove the color and nutrients still retained by the wastewater, they pass to a lime filter which completes the removal of the organic contaminants at 75-85%, then they pass to a tezontle filter that It serves to eliminate the odor and remove the color and finally to remove the nutrients still retained by the wastewater, the waters are passed to a pond with floating aquatic plants when leaving the filters. The removal of some components such as: nitrogen, phosphates, some heavy metals is carried out in this stage with an efficiency higher than 85%. The effluent can be sent to an emitter and reused in irrigation systems, or other internal uses such as sanitary, or planting and cultivation of fish, a unique feature of this water treatment system.

The gas produced in the decomposition process inside the reactor is mainly methane gas, which can be used as fuel in the kitchen for food preparation and the use of this gas as an alternative to produce electrical energy could allow the system to pay for itself. itself in the medium term, another unique feature of this water treatment system.

We believe that the use of gas is important not only to reduce the use of other fuels, but also because the effect of methane gas that accumulates in the atmosphere produced worldwide in decomposition processes, has a greater impact on the greenhouse effect than the bioxide of carbon due to an even higher specific heat (50 times more than CO2). The advantages of this type of system are: first that it can treat high flows of wastewater, and strong organic loads, as well as respond to sudden changes in both the flow and the organic load; second, they require less volume than an upflow filter to treat the same amount of water. During the start-up period, the contaminant removal efficiency of the enzyme reactor (rea) begins to give a treatment of 70-80% efficiency, adding the hydrolase enzyme load. The start-up process must be observed by trained personnel and requires certain laboratory analyzes to ensure that the process is properly established. After the start-up period they are very easy to operate, and the only maintenance they require is to empty the sludge every year, or according to the specific results of monitoring for each reactor. The efficiency of the system can be susceptible to large concentrations of solvents, oils and pesticides, due to the high mortality that these cause in anaerobic microorganisms. However, concentrations of this type are not expected within this project.

Description of the proposed system.

The objective of the ecological wastewater treatment system is to pass through three stages: a pre-treatment stage, a second stage of anaerobic enzymatic reaction and finally a post-treatment stage. The pre-treatment is integrated by a sand trap, double grid, and a pump station is included. The second stage, also called primary treatment, is constituted by one or more anaerobic enzymes reactors (rae) in cascade or in ascending flow series and finally the post-treatment constituted: hydrated lime filter, a tezontle filter and a marsh, a system of uptake of metabolic elements based on water lily and an emitter. This combination of stages allows the upstream anaerobic enzymes (rae) to eliminate between 75% and 85% of the contaminants present in the water, which considerably reduces the post-treatment area. In the pre-treatment, the sludge and waste are collected or separated as plastic, branches, sand and others; in the primary treatment, most of the organic matter present and dissolved in the water (carbon) is eliminated, in the post-treatment it is air and eliminates nitrogen, phosphorus and potassium with the incorporation into the metabolic system of the water lily that develops with the planting of these plants on the bog and whose efficiency is around 90%.

Description of the component units of the treatment plant: 1. -Unit of pre-treatment: The water coming from the discharge drains of the toilets enters the treatment plant to a sand trap, which is integrated with two or three retention grids at the bottom of it where it is separated by induction and gravity the sand, stones and other materials such as papers, plastics, rags, fruits, and garbage in general, etc., in order to be removed and to avoid obstructions and plugging in the hydraulic conduits and prevent them from reaching the pumping station to avoid faults, a physicochemical and bacteriological analysis is carried out at this point of entry to the sand trap The difference with other dealers lies basically in the unbalanced discharge tube, with 5 ° of deviation to produce zigzag flow as well as the retaining grid at 90 ° with ascending vertical sliding guide. 2. - Pumping channel: This station must receive the fluid with the organic load and send it to the elevated box by means of a pump it has the characteristic that it is of cylindrical form of a clay paste, generally of orthohedral form, obtained by molding, drying and firing At high temperatures of approximate dimensions of 24 x 11.5 x 6 cm, said carcomo also has a control with set-point level for start and stop. 3. - Distribution box or elevated box: This tank has the function of receiving the fluid with the organic load sent by the pump from the pump station to distribute by gravity to the reactor the fluid that will be subjected to digestion. It acts as a balance tank, so care must be taken that the volume received does not exceed the volume of the same tank, it must synchronize or limit the level of the tank with the level of the distribution tank, trying not to exceed more than 75% of the level of the tank. the distributor box to prevent spillage.

It acts as a balance tank, in addition to dislodging by gravity through a 15 ° tube to avoid producing foam. 4. - Enzymatic anaerobic reactor (RAE): The reactor in normal form will retain the sludge for more than 20 hours until it reaches a considerable volume that allows it to reach the exit level where a tube is placed where the discharge is made to the tank. sludge once these have been degraded. The resulting liquid, once there is also a discharge level (time not exceeding 20 hours of residence) will pass to the lime tank, discharging into a small waterfall. Each time organic load is introduced into the reactor, it will push the already treated liquid and simultaneously exit the tank with lime. To the reactor, the recommended enzymatic load of the hydrolases type of vegetable origin must be added to help the digestion, this will act as a catalyst on the organic load accelerating the reaction and producing the biogas.

The novelty of this reactor lies basically in its structure as it is composed of three parts: head or dome, cylindrical body, and conical bottom, in addition to the discharge of fluid from the distributor box through a volcanic rock filter in addition to contain a plurality of pvc tubes from the dome to the bottom of the reactor for the introduction of the upper distributor ring of the fluid with a slight inclination of 15 °, the inclination of the cone is 30 ° and contains a 40 ° or 1.8 m inclined tube of height above the tank, of PVC for the evacuation of sludge to the tank of sludge likewise the water outlet of the reactor to the tank with lime has a 5o slope, finally the reactor water falls into a box to produce a waterfall and start the aeration process. 5. -Lime tank: This tank receives the liquid that comes from the reactor, goes to the waterfall and from there it is put in contact with a solution at 30% w / v of CaO. In this container the lime acts as a flocculant that precipitates salts forming mainly carbonates and bicarbonates, but also acts as a bactericide with the purpose of killing the bacteria that will contaminate the water, increases the pH a little and clarifies the water. These flocs serve as nutrients to the flora and favor aquatic life and the difference with the common tanks that has its flow distributor ring with 4 outlets, it is cylindrical in shape, the solution is given in proportions of 20 -30% p / v of CaO in water in addition to having a drain pipe directed to the sludge pit for residues and flocs 6. -Tezontle filter: The fluid coming from the tank with lime is communicated through the bottom with the tank of tezontle this compound by iron dioxide; with a vesicular, bubbled and porous texture that retains the floccules and bactericidal cream, has the ability to filter, but in addition to carry out oxidation-reduction reactions and retain sulfate-reducing bacteria originating from enzymatic degradation and the filter has an approximate thickness of 30 cm in height approximately and from 3 to 1/32 inches in diameter. 7. -Ciénega with water lily: The marsh, which is built in a zigzag or parallel channels is to increase the residence time of water from the filter. In each section or channel the flow of water is retained with a tezontle barrier that finishes filtering, retaining the aquatic lily sown and contributing to the aeration. The water level is low to help the ultraviolet radiation perform some photosynthetic and photo catalytic reactions with lily and tezontle, also allowing the absorption of nitrogen, phosphorus and sulfates. The liquid is sent to an emitter with cascade tapping to be finally discharged to the catchment lagoon, 20% or more of this marsh is cascaded. 8. -Fuel tank: The gas formed in the bioreactor is usually methane and CO2, which is sent to a gas tank by density and pressure difference. When this is introduced into the gas tank, it moves up or down by moving a bell over the metal guide that must be perfectly sealed to prevent leaks. The gas can be used for combustion or other use and can be sent to vent through a line and from there to the burner. It should be noted that the gas is separated from the water and that the displacement hood on an upward guide 9. -Lange tank: The sludge coming from the reactor will take time to leave, and depending on the organic load that enters the reactor, these must be deposited in the sludge tank automatically by different levels and pressure. The sludge will dry naturally obtaining an organic fertilizer with a great diversity of nutrients. This tank contains a bottom with filtering gravel for leachates and a runoff to another tank with a pump to send the liquids to the carcomo. 10. -Operator room: Here all the personal and plant safety equipment will be concentrated.

Detailed explanation Pre-treatment unit and pumping station (upt) Waste water enters the sand trap and here sand and other materials that could clog the hydraulic lines are separated by induction and gravity, next to this, the 2 (two) grates of different granulation pitch thicknesses and placed inside the sand trap It also separates trash plastic bags that enter with the water passing to a pumping borehole where some of the sand, clay and residual water are temporarily stored, from here the water is pumped by means of 2 (two) pumps enzymatic anaerobic reactors or reactors.

Enzymatic anaerobic reactors (rae): Waste water. The water that enters the anaerobic Enzimatico reactor (rae), initiates the process of digestion in an immediate way by the presence of hydrolase enzymes where organic matter is eliminated with an efficiency between 75% and 85%. In the elimination of carbon it is converted into carbon dioxide and methane Sludge tank The solid particles that are formed can be retained up to 00 days, enough time for them to be digested forming an active biomass that allows water treatment. Bacterial growth during the annual development requires evacuation, so it is necessary to pass through a filtration process of 10 days or more in order to keep the settleable solids within the norm, in addition the amount of sludge depends on the number of population or of the organic load that can increase or decrease, the treatment of sludge from this, can vary and can be used as organic fertilizer that may have a formulation depending on the use that you want to give, for example organic crops of plants, manufacture of humus or humic acid, etc. The liquid that accompanies the fresh sludge for drying. It is stored in an annexed tank by gravity runoff and is sent back to the pit for its best use taking into account that this liquid contains high amounts of enzymes and autochthonous bacteria that can accelerate the digestion process when they are sent back to the reactor. It is another of the unique characteristics of this treatment system.

Filters The water that comes out of the reactors is aerated by a body made in cascade type work, and is immediately passed through a lime filter and then the tezontle filter to eliminate odors and retain sludge or soluble particles and suspended in the water and thus ensure a clarified water.

Cal filter. The lime tank has two purposes, the first to eliminate bacteria or microorganisms that are present in the water and mud and act as a neutralization pit where you can regulate the pH of the water.

Tezontle filter: the tank tezontle has the purpose of eliminating odors and colors in the water.

Ciénega constructed. -The ciénega is part of the post-treatment and reduces the concentrations of nitrogen, phosphorus and potassium present in the wastewater, through the incorporation as nutrients of the biological cycle of the aquatic lily that is planted for this purpose. The marsh should have certain characteristics of shallow depth, and conduct water through channels in a staggered way to give it a turbulence, within the marsh that will allow more residence time. A part of the marsh (20%) should be built in the form of a waterfall to help the aeration. It is another of the unique characteristics of this treatment system.

Emitter: This conducts the treated water to the discharge channel that has been specified for a particular use either irrigation, in the culture of fish or that is incorporated into streams of streams or tributaries of rivers.

V.-biogas The load of the enzymatic anaerobic reactor, once the digestion begins, generates gas that is sent to a storage tank and that can be used as fuel gas for the use of food processing in the kitchen, or as producer of electric power. Important feature of this treatment system.

Sizing of the wastewater treatment system.

TO). Residual water characterization Due to the current existing characteristics, it has been foreseen that the drains will only conduct only black and gray water, so it is expected to receive wastewater in the treatment system with moderate to concentrated concentrations, so it is recommended to monitor at least several times at several points. per year, to obtain real representative data of physical, chemical, bacteriological and biochemical analysis and for calculation purposes the following data for the treatment system have been estimated. dbo5 150 to 250 mg / l dqo 300 to 500 mg / l dqo / dbo 2 ss 3 to 3.5 ml / l st 1, 000 to 1, 250 mg / l flow rate (q) = l / s = m3 / hr. = m3 / day "per capita" = 200 l / hab. Day Equivalent population (p) = q / "per capita" = _ inhabitants Contribution of fresh muds = (ml / l) (l / hab. Day) = L / room Day organic load = (mg dqo / l) (l / day) = g dqo / hab. Day of the 200 l / hab. Day of consumption only 75% is recovered: organic load = (mg dqo / l) (l / inhab Day) = g dbo / hab.dia contribution of fresh mud = (ml / l) (l / room day) = l / hab Day B) design parameters of the anaerobic reactor Maximum organic load applied up to kg. DQo / m3day hydraulic load < m3 m3 / m3 reactor / day retention time (trh) 20 hours (average) minimum height of the mud layer m maximum ascending speed m / hr. number of injectors m2 Expected treatment efficiency 75 to 85% C) design parameters of the built-up marsh maximum applied organic load < kg. Dqo / m3 day hydraulic load < m3 / m2 day retention time (trh) 4 hours Expected treatment efficiency 80 to 95% D) biogas production theoretically for every kg of dbo removed will occur I of methane. for domestic drains is from x to x m3 chVhab. Year x l / hab. Day m3 biogas / m3 reactor day x I biogas / kg dqo Average conversion: dVdqo is 71% see input and output sst relations (kooijmans et al) Treatment system data: expected daily organic load: (kg dqo / day) (inhabitants) = kg dqo / day expected daily volumetric load (m3 / room day) (room) = m3 (x) = m3 The determination of the volumetric load is a limiting factor, so the volume of the digester is calculated based on an average hydraulic retention time of 20 hours useful digestion volume = (m3) / (24) (20 hrs) = m3 To cover said volume of digestion, the construction of an enzymatic anaerobic reactor of x m3 is proposed. The stone packing used in the reactors will have a diameter between 4 and 6 inches and a maximum height of 30 cm. biogas production 0. 200 m3 biogas / kg dqo / day = 0.200 (x) = x m3 sand trap As the grit trap is designed for sanitary drains, it does not present sudden flow changes, so the following data are considered: maximum depth x meter long x meter width x meter The inlet and outlet of the sand trap must be at the same level The grilles (two) must have a space no larger than x cm between bars, inside a frame and angle frame, which facilitates cleaning.

Pump station and its equipment To pump the wastewater to the enzymatic anerobic reactor, by its arrangement it is not possible to do it by gravity, so a lift station equipped with 2 (two) immersible open impeller pump is proposed.

Enzymatic loading (eh) of the bioreactor The load based on hydrolaces will be in a ratio of 1 kg. Dqo / 0.1 kg. Eh, so it requires kg. Eh / day worked at room temperature.

Calculation of the size of the sludge drying tanks fresh mud: (ss) ml / l (l / inhab. Day) (hab.) = l / hab. Day = m3 / hab. Day (365 days) = m3 / 2 annual downloads, one every 6 months = x m3 a tank with a total area of m2 is required the maximum thickness of the mud layer (wet) = m total volume of = m3 height: m percolate time of leachates: hours.

With this area it is possible to evacuate the sludge in a single day and the drying of the sludge in 3 days maximum.

The Serra quick lime tank with a volume of m3 taking into account the marsh's feeding volume with an area of m2 m in diameter and a height of m.

The activated carbon or tezontle filter will have the same characteristics as the quick lime tank Calculation of the built ciénega The calculation is made from the following data: maximum applied organic load < 0.105 kg dqo / m3 day hydraulic load < 1.36 m3 / m3 day Retention time (trh) 4 hours expected treatment efficiency 80 to 95% (data taken from "biogas forum" .1996. 1v n ° 62 edited by borda bremen german federal republic) organic loading entrance to ciénega (kg.) (m3) (hab.) (0.95) = kg. volumetric load m3 / day Already organic loading in this case is irrelevant, therefore the calculation of the size of the marsh is based on the retention time (trh), of 4 hours. volumetric load / 4 (efficiency) = volume v m3 / 4 (0.95) = m3 calculated area d m2 (0 x 0 m) depth m volume d m3 trh > 4 hours To oxygenate the water, it is proposed that the exit of the marsh is built in the form of a waterfall to achieve the objective and be within specifications.

Sowing of aquatic plants in ciénega The nutrients from the effluent pollutants of the anaerobic enzyme reactor (rae) that are discharged into the marsh are mainly nitrogen, phosphorus and potassium and these are removed by the aquatic plants found in the marsh, which incorporate the nutrients in their metabolism The plant to be sown is of the family type of water lilies, since along with algae and nopal have excellent purifying properties of contaminated water, besides removing some heavy metals also capture carbon dioxide and carbon monoxide. This last step is carried out after the anaerobic reactors have started operating and in the marsh, the ultraviolet light emitted naturally also carries out photodegradation.

The water lilies of the family Eichhornia crassipes, is found floating on the surface of streams and lakes of fresh water, as well as in marshes and dams. It is considered free since its roots are not fixed to any substrate.

They have a feathery, fibrous root with many branches. The stem is thin and the pesciolos that are spongy and inflated are found around it. The leaves are lobed with a characteristic green color because they are very shiny. Many times the pesciolo and the leaves can be submerged or not; the inflorescences start from a central spike (weldon et al, 1973).

The water with lily, which forms the ecosystem, contributes to the improvement of water quality, especially the bacteria associated with the root, since it has been observed that with them the plant is capable of absorbing nutrients on its own.

In addition, the plants provide shade that prevents the growth of algae allowing them to act as a biological filter, clarifying and purifying water (Karpiscak et al., 1992).

These lilies will be collected in nearby wetlands and streams in the vicinity of where the treatment plant will be built and will be planted over the bog Efficiency of expected treatment, balance of chemical oxygen demand and current ecological regulations The main objective is to eliminate the organic matter in the proposed treatment system as long as the next flow of the dqo is followed, based on the concentration of one liter of wastewater. concentration of water entering Enzymatic anaerobic reactors: 500 mg dqo expected treatment efficiency in digesters (minimum) 70% dqo eliminated in the primary treatment 350 mg dqo dqo entering after treatment 150 mg dqo expected treatment efficiency in built ciénegas (minimum) 65% dqo eliminated in post-treatment 97.5 mg dqo. expected discharge quality 52.5 mg dqo The value of the discharge is below the concentrations indicated in the current regulations, which considers a maximum value of 150 mg dqo / l.

Fecal coliforms With respect to fecal coliforms, the current norm applied to a recipient body type "a" must be complied with, according to the law published in the official journal of January 6, 1997, which considers a maximum of 1000 coliforms for every 100 ml of treated water.

Fecal coliforms are mainly killed in the anaerobic enzyme reactor due to the reaction conditions and a strongly reducing environment due to enzymatic metabolism. Therefore, chlorination is optional, although it is not necessary in the final stage. The maximum permissible limits for discharges to receiving bodies type "a", is 2000 nmp / 00 mi, and monitoring carried out at similar plants, their coliform discharges is less than 1000 nmp / 100 mi.

Process and operation It is called the "start" of the process to the transition period of the reactor that begins once concluded its construction and ends when the characteristics of the biomass are reached, in stable state, the conditions that were assumed in the design (specific activity, concentration , hydrodynamic behavior, etc).

The starting period is usually the stage considered the most unstable and difficult in the operation of a rae. With the addition of the enzyme, the addition of an inoculum is not necessary for the development of the biomass since it can adapt and lose its desirable characteristics to carry out the degradation.

During this period, a series of biochemical changes are initiated within the reactor that destabilize the system, which means that the thermodynamic and environmental conditions must be controlled very well in order to allow the bacterial population to develop properly in order to degrade the substrate.

To avoid setback during start-up, the following recommendations should be taken into account: • In case of adding an inoculum or seed, this should be of good quality and in an adequate minimum quantity, which should have a possible methanogenic activity, with good sedimentation characteristics and, if possible, be adapted to the substrate that is going Apply. Sludge between 10 and 15 kg. Ssv / m3 reactor are considered to be of good quality.

• The process conditions (ph, temperature, nutrients, etc.) should favor bacterial growth, so strict control should be observed if necessary.

• It is recommended to recycle a fraction of the treated water in order to expand the sludge bed to favor the dragging of inert fine solids, in addition to increasing the residual water-bacteria contact.

• The lime filter is charged with a solution of kg of lime in I of clean water pre-filled in an independent tank to the filter and recharging the loss of the 20% of the solution (approximately) with kg of lime in l. Of clean water per week.

Under conditions of continuous operation, an anaerobic enzyme reactor needs 6 months to a year to reach the values stipulated in the design. On the other hand, the conditions necessary for the proper functioning of the sludge process in anaerobic digestion require: -Avoid abrupt temperature variations -maintain the pH between 6.5 and 7.5, either adding nutrients or controlling process parameters. -evitate in the toxic substrate during the process, such as nitrogen (nh4 +, nh3, s2) etc.

-To avoid toxic organic overloads beyond the tolerable limit for the process. -the existence of nitrogen and phosphorus in the waste must have a good relationship with carbon.

The main parameters used in the evaluation of an anaerobic digestion process are: • Volume and composition of the gases produced • Temperature • Ph • Volatile fatty acids (agv) • Alkalinity • Oxido-reduction potential (redox) • Dqo / dbo • Total and volatile solids • Relationship c / n / p • Ammonia • Sulfates / sulphites • Heavy metals • Alkaline and alkaline earth metals Some determinations can be omitted, depending on the characteristics of the substrate to be treated once its behavior is known.

In the case of primary drainage sludge, the range of alkalinity is between 2500 and 4000 mg / l expressed as carbonates (cacos), and volatile fatty acids range between 50 and 150 mg / l as acetic acid (C2r 02). Regarding ph, most authors consider that 6.8 to 7.2 corresponds to an optimal condition, although digestion is possible between the extreme limits of 6.5 to 7.8. In general, if the digesters work well, the redox potential is of the order of -500mv, which indicates a high state of anaerobiosis and reducing capacity of the medium.

Regarding nutrients, the recommended proportions are: Carbon / nitrogen ratio = 30 Nitrogen / phosphorus ratio = 5 Ratio dqo: n: p = 100: 5: 1 or 330: 3: 1 (complex substrates) Maintenance of the treatment system The maintenance of the equipment must be scheduled considering that the plant must work continuously during the 365 days of the year.

The entrance of the wastewater stream should be diverted to an auxiliary storage tank in case of having this, since it is not advisable to divert it to the emitter's current.

The sand trap must be cleaned at least twice a year, taking advantage of the mud evacuation. The grid should be cleaned daily to remove garbage or bags that are retained.

The pumping station should be washed every time the level drops to the minimum and try to have a relief pump for periodic annual maintenance.

The reactor should be cleaned at least twice a year and the addition of the enzymes should be biannual or annual depending on the organic load.

The operation of extraction of bacterial sludge to the deposit made annually, and the objective is to clean and drain the sediment (bacterial sludge) inside the reactor through the tube and valve "in diameter, the sludge is evacuated and mixed with the lily eliminated, already dried can be used as fertilizer for general plants and green areas since it is totally harmless.

The tank filter should be cleaned and drained every three months and changed at least once a year.

The lime filter and the tezontle filter must be drained and cleaned every six months and their load changed at least once a year. Control the amount of water lily in such a way that it only covers the water film of the swamp, removing and pruning from time to time the surplus of these, the eliminated lily will be deposited in the sludge tank with the objective of mixing it with the bacterial sludge. The storage system and gas burner should be monitored to prevent leaks. The general area must be constantly clean for its proper functioning.

In the applied invention, an anaerobic enzyme reactor (rae) is included as an innovation, which has the particularity of increasing the degradation of contaminants and microorganisms present in wastewater that works with hydrolase enzymes that transforms the organic matter present in the wastewater up to 85% at a low cost It has been possible to improve the obtaining of enzymes so that they are purer, which represents the following advantages over the fermentation products: • More specific action in its catalytic function · Predictable and controllable activity and • It is possible to use higher concentrations of the substrate.

The main sources of enzymes used in the food industry are of different origin: a) Vegetable: Lipases and pectinoesterase are made from soy, castor and citrus fruits: alpha-amylase is extracted from the wheat germ. Proteases are obtained from papaya, fig, pineapple and horseradish peroxidase. b) Animal: Renin, pepsin, trypsin, chymotrypsin, catalase and pancreatic lipase are of animal origin; c) Microbial: The enzymes of the fungi: Aspergillus flavus, orycae and Niger of Bacillus subtilis have proved to be of great use in the food industry.

The enzymes obtained should be purified and isolated by being subjected to a clarification and concentration (liquid preparation) or desiccation (solid preparation) and recourse is also made to methods of isolation and purification of enzymes on a large scale, which is mainly achieved by the following processes: By precipitation, Dialysis, Ultrafiltration, Electrophoresis, Chromatographic Fractionation.

Combining these procedures with others based on high voltage electrophoresis, cataphoresis and electrodialysis, separations of complex mixtures of enzymes are now achieved.

The control of all these stages in its most rigorous form, is necessary to ensure the maximum performance and reproducibility, safety and quality of the enzymatic products obtained.

The enormous number of reactions catalyzed by enzymes and the specificity of the individual enzymes mean that they are potentially of great industrial value. However, their cost is exacerbated by applying them as reagents in soluble form, since their loss occurs once they are used. Although the enzyme to be regenerated in the process could be used many times, its separation from the reaction mixture is not economically feasible. Hence, the possibility of immobilizing the enzymes on inert supports has been an important advance, thus retaining a large part of their original catalytic activity. Since enzymatic reactions take place in an aqueous medium, the support matrix must be insoluble in water, but so hydrophilic that it guarantees good contact with the reaction medium.

In the treatment of wastewater, enzymatic reactors have been favored by the presence of hydrolase enzymes that help the digestion process.

Enzymatic reactors are using a mixture of enzymes with similar characteristics to induce the formation of biogas, this is the case of the package that is presented today to transform the organic load into methane, carbon dioxide, an intermediate (1, 3 dibutene), carbon and H20. This mixture is formed by Bromelain, Pectinase, Protease, Peroxidase and Rhodophyeae: Enzyme ? 2 C02 +2 H20 + C4H8 - E C4H8-E? 2 CH4 + 2 C + E- The mixture of CO2, CH4 and H20 form THE BIOGAS. Carbon is part of the sludge that is later transformed into humic acid.

For each Kg of organic load it is required to activate the reaction with 0.1 Kg of enzyme. It is important that the enzyme is stored at low temperatures, and that it is replenished continuously.

The enzyme that is provided works at pH between 3-9, in granular form 16-100 mesh, dissolved in aqueous phase with a density 0.9 g / cm3. It has been characterized with spectrophotometric technique with a band of 265 nm. Its kinetics indicates reactions of the first order.These enzymes are inhibited by the presence of strong bases such as KOH, NH4OH (pH 1.5), ammonia, cleaning products, oils, fats, surfactants, waste of heliographic development liquids.

For these enzymes, the Precipitation method was used and the procedure was as follows: -De the skin of citrus Pineapple, orange, papaya, radish and river seaweed) dehydrate at 45 ° C. 2. - Grind or grind to a powder between 40 to 100 mesh 3. -For each 200 g of powder add one liter of distilled water 4. -Prepare a 10% saline solution with NaCl 5. -Add the saline solution to the liquid with powder and do the extraction at 10 ° C. 6. -From the initial fermentation the formation of enzymes increases and can be used with the liquid or filtered. Both the liquid and the powder contain enzymes. 7. -The content of this mixture of enzymes is 40% bromelain, 25% pectinase, 15% protease, 5% peroxidase and 15% rhodophyeae.

For each Kg of organic load add 0.1 kg of enzyme.

Claims (4)

CLAIMS Having sufficiently described my (our) invention, I consider (We consider) as a novelty and therefore, claim (claim) as of my (our) exclusive property, contained in the following clauses: (read this text and delete it) At least there must be a claim to be entitled to a filing date, since here is the subject that is going to be protected in the patent

1. - Ecological system of wastewater treatment using an anaerobic enzyme reactor characterized in that it is composed of: -Unit of pre-treatment; The water coming from the discharge drains of the toilets enters the treatment plant to a sand trap, which is integrated with two or three retention grids at the bottom of the same where induction and gravity separates sand, stones and other materials such as papers, plastics, rags, fruits, and garbage in general, etc., in order to be removed and to avoid obstructions and clogging in the hydraulic conduits and prevent them from reaching the pump station to avoid failures. A physicochemical analysis is carried out and Bacteriological at this point of entry to the sand trap The difference with other dealers lies basically in the discharge tube not centered, with 5o of deviation to produce zigzag flow as well as the retaining grid at 90 ° with ascending vertical sliding guide; - Pump parking; This station must receive the fluid with the organic load and send it to the elevated box by means of a pump it has the characteristic that it is of cylindrical form of a clayey paste, generally of orthohedral form, obtained by ing, drying and firing at high temperatures of dimensions approximate 24 x 11, 5 x 6 cm, said carcomo also has a control with set-point level for start and stop. - Distribution box or raised box: This tank has the function of receiving the fluid with the organic load sent by the pump from the pump station to distribute by gravity to the reactor the fluid that will be subjected to digestion; It acts as a balance tank, so care should be taken that the volume received does not exceed the volume of the tank by means of a 15 ° tube to avoid producing foam, the level of the tank should be synchronized or limited with the level of the distribution tank trying not to exceed more than 75% of the level of the distribution box to avoid spilling. - Enzymatic anaerobic reactor (RAE), consists of three parts: head or dome, cylindrical body, and conical bottom, in addition to the discharge of fluid from the distributor box through a volcanic rock filter in addition to containing a plurality of pvc pipes from the dome to the bottom of the reactor for the introduction of the upper distributor ring of the fluid with a slight inclination of 15 °, the inclination of the cone is 30 ° and contains a 40 ° inclined tube or 1.8 m height above the tank, pvc for the evacuation of sludge to the sludge tank as well as the water outlet from the reactor to the tank with lime has an inclination of 5 °, finally the reactor water falls into a box to produce a waterfall and start the process of aeration. - Lime tank: Receives the liquid that comes from the reactor, passes to the waterfall and from there it is put in contact with a solution at 30% w / v CaO; In this container the lime acts as a flocculant that precipitates salts forming mainly carbonates and bicarbonates, but also acts as a bactericide with the purpose of killing the bacteria that will contaminate the water, increases the pH a little and clarifies the water; These lobules serve as nutrients to the flora and favor the aquatic life and the difference with the common tanks that has its flow distributor ring with 4 outlets, it is of cylindrical shape, the solution is given in proportions of 20 -30% p / v of CaO in water in addition to having a drain pipe directed to the sludge pit for residues and flocs; - Tezontle filter: The fluid coming from the tank with lime is communicated by the bottom with the tank of tezontle this compound by iron dioxide; with texture vesicular, bubbled and porous that allows to retain the floccules and cream bactericide, has the ability to filter, but in addition to carry out oxidation-reduction reactions and retain the reducing sulphate bacteria coming from the enzymatic degradation and the filter has a thickness of approximately 30 cm approximately 3 to 1/32 inches in diameter; -Ciénega with water lily: The marsh, which is built in a zigzag or parallel channels is to increase the residence time of water from the filter; In each section or channel the flow of water is retained with a tezontle barrier that finishes filtering, retaining the aquatic lily sown and contributing to the aeration; The water level is low to help the ultraviolet radiation perform some photosynthetic and photocatalytic reactions with lily and tezontle, also allowing the absorption of nitrogen, phosphorus and sulphates, the liquid is sent to an emitter with cascade tapping to be finally downloaded to the catchment lagoon, 20% or more of this marsh is in the form of a waterfall; - Biogas tank: The gas formed in the bioreactor is usually methane and CO2, which is sent to a gas tank by density and pressure difference. When this is introduced to the gas tank, it moves up or down by moving a bell over the metal guide that must be perfectly sealed to prevent leaks; The gas can be used for combustion or other use and can be sent to vent through a line and from there to the burner; It should be noted that the gas is separated from the water and that the displacement hood on an upward guide; - Sludge tank: The sludge from the reactor will take time to leave, and depending on the organic load that enters the reactor, these must be deposited in the sludge tank automatically by different levels and pressure; The sludge will dry naturally obtaining an organic fertilizer with a great diversity of nutrients; This tank contains a bottom with filtering gravel for leachates and a runoff to another tank with a pump to send the liquids to the cone; - Operation room: Here all the personal and plant safety equipment will be concentrated;

2. - Ecological system of wastewater treatment using an enzymatic anaerobic reactor according to the previous claim, characterized in that it comprises the following stages: a) Pre-treatment unit and pumping station.- The waste water enters the sand trap and here sand and other materials that could obstruct the hydraulic lines are separated by induction and gravity, next to this, the 2 (two) grids of different thicknesses of granulation step and that are placed inside the sand trap, also separates plastic bags garbage that enters with the water passing to a lift station where it is also stored part of the sand, clay and residual water temporarily, from here the water is pumped by means of 2 (two) pumps to the reactor or enzymatic anaerobic reactors; b) Enzymatic anaerobic reactor.- The residual water entering the anaerobic enzyme reactor (rae), initiates the digestion process in an immediate way by the presence of hydrolase enzymes where organic matter is eliminated with an efficiency between 75% and 85%. %; In the carbon removed this is converted to carbon dioxide and methane; c) Sludge tank: The solid particles that are formed can be retained up to 100 days, the liquid that accompanies the fresh sludge for drying, is stored in an annexed tank by gravity runoff and is sent by re-pumping to the sump for its better use taking into account that this liquid contains high amounts of enzymes and autochthonous bacteria that can accelerate the digestion process when they are sent back to the reactor; d) Filtering.- The water coming out of the reactors is aerated by a body made in cascade type work. It is passed through a lime filter and then to the tezontle filter to eliminate odors and retain sludge or soluble and suspended particles. in the water and thus ensure a clarified water. -Lime filter.- The lime tank has two purposes, the first to eliminate the bacteria or microorganisms that are present in the water and the mud and act as a neutralization pit where the pH of the water could be regulated; - Tezontle filter: the tezontle tank has the purpose of eliminating odors and colors within the water; -Cienega.-The marsh is part of the post-treatment and reduces the concentrations of nitrogen, phosphorus and potassium present in the wastewater, through the incorporation as nutrients of the biological cycle of the water lily that is planted for this purpose. The marsh should have certain characteristics of shallow depth, and conduct water through channels in a staggered way to give it a turbulence, within the marsh that will allow more residence time. A part of the marsh (20%) should be built in the form of a waterfall to help aeration; e) Emitter: This conducts the treated water to the discharge channel that has been specified for a specific use, whether irrigation, in the culture of fish or that is incorporated into the currents of the streams or tributaries of the rivers;

3. - Ecological system for wastewater treatment using an anaerobic enzyme reactor according to claim 1, characterized in that the enzymes used in the bioreactor work at pH between 3-9, in granular form 16-100 mesh, dissolved in aqueous phase with a density 0.9 g / cm3;

4. Ecological system of wastewater treatment using an enzymatic anaerobic reactor according to the previous claim characterized in that the enzymes used in the bioreactor were obtained by precipitation as follows: a) From the citrus peel Pineapple, orange, papaya, radish and river seaweed) dehydrate at 45 ° C; b) Crush to a powder between 40 to 100 mesh c) For every 200 g of powder add one liter of distilled water d) Prepare a 10% saline solution with NaCl e) Add the saline solution to the liquid with powder and do the extraction at 10 ° C; f) The content of the final concentrate should contain 40% bromelain, 25% pectinase, 15% protease, 5% peroxidase and 15% rhodophyeae. For each Kg of organic load add 0.1 kg of enzyme.