WO2008000871A1

WO2008000871A1 - Equipment for biological purification of wastewater

Info

Publication number: WO2008000871A1
Application number: PCT/ES2007/000369
Authority: WO
Inventors: Julio VALDES GARCÍA
Original assignee: Biotratamientos De Aguas, S.L.
Priority date: 2006-06-21
Filing date: 2007-06-20
Publication date: 2008-01-03
Also published as: ES2301370B1; ES2301370A1

Abstract

The equipment is configured as a single digester for performing hydrolytic and methane-generating anaerobic digestion and purifying wastewater, which improves habitat compatibility between bacteria, optimizing appropriate ecological niches and creating a new habitat in which nitrogen-reducing bacteria are formed. The equipment is formed by a body with two concentric walls (1) and (2), forming an internal body in which there are ceramic pieces (8) where anaerobic digestion of the water takes place by means of ascent through said ceramic block (8), whilst, at the perimeter, there is a chamber (5) with a lower compartment (6) where methane-generating digestion takes place, all this with conduits (19') and (24) for the recirculation of water towards a new digestion receptacle and conduits for the discharge of gases (29), and also a lower outlet (17) for sludge.

Description

EQUIPMENT FOR BIOLOGICAL WATER TREATMENT

RESIDUALS

D E S C R I P C I Ó N

OBJECT OF THE INVENTION

The present invention relates to a biological wastewater purification equipment, where the purification is based on anaerobic, hydrolytic, fermentative, acidic and methanogenic digestion, presenting the particularity of being configured as an anaerobic digestion equipment that includes a single digester. which, according to an appropriate design thereof, the corresponding ecological niches are optimized, creating a new habitat in which nitrogen-reducing bacteria are formed.

The equipment has its application within the industry dedicated to the purification of urban wastewater or industries that need to purify water with high organic matter content, especially the removal of primary sludge from water purification plants with aerobic systems.

BACKGROUND OF THE INVENTION

In the processes of biological purification of wastewater with high organic load, whether they come from cities (urban wastewater) or agro-food industries, livestock farms in a housing regime where large amounts of slurry (stool, livestock excrement formed by solids and liquids), etc., anaerobic digesters or reactors are used, being able to be of a single digester without phase separation, or high speed with phase separation.

In single-digester systems, they are accumulation reactors with a hydraulic residence time that varies between 15 and 21 days, so that during the process normally solids greater than 1 millimeter contained in the water are separated, before the entry of the liquid in the anaerobic digester. They are also known as DAC type of central activity.

Anaerobic fixed or mobile bed reactors are also known which can be divided into the following systems:

- Up flower anaerobic sleugde blanker (UASB)

- Fluid bed or expanded bed reactor (BIOFLUID system)

- Fixed bed reactor with plastic or ceramic bacteria fixing support. - Anaerobic filters.

- Two phase reactors.

The contact reactor is a unique reactor that has devices for internal agitation, such as the injection of the gas itself produced to improve the biomass mixture in the digester and stir the liquid inside the digester itself, achieving a reduction of residence times hydraulics.

However, the concentration of different types of bacteria within a single digester it destabilizes the process, due to the increase of a colony of bacteria with respect to the other or others, it also destabilizes the pH inside the digester, producing very frequently the clogging of this type of digester.

In addition, there is a loss of purification performance, as well as a low production of biogas. Therefore, it is an essential point for the process that the bacterial balance of the biomass for the same organic load be digested at different times by the acidic (hydrolytic, fermentative) and methanogenic (acetoplastic and hydrogen-rows) bacteria. For this reason, the increase of a population in the hydrolysis phase entails a decrease in methanogenic bacteria causing the process to be destabilized, losing efficiency, as it is not able to eliminate the organic components of the waste to be treated in an adequate time, all due to The different reproduction rate of bacteria.

In the same way, the central activity system (DAC), although it improves the performance of the contact reactor with an internal decanter that ensures a higher concentration of bacterial biomass inside and facilitates the precipitation of easily sedimentable inert materials, does not solve the problem of the cohabitation of bacteria with conflicting habits requirements, so that their purification times or hydraulic residence time for the purification of, for example forty cubic meters of water per day, which requires a digester volume of approximately 500 cubic meters, It would be twelve and a half days, with 80% clearance for chemical oxygen demand, and 95% for biological oxygen demand.

This system involves building large digesters with high capacity volumes to treat low volumes of wastewater, etc., so that the economic investment is high to treat low purification flows.

The UASB system improves performance, thanks to a greater granulation of anaerobic biomass and the use of sludge bed, although it still does not resolve the differentiation of bacteria habitats, not paying attention to the different reproduction rates or fixing a Neutral pH from the hydrolytic phase, so it easily destabilizes with the substantial variations of the organic load to be treated, substantially altering the performance of the system.

The reactors of fluidized bed or expanded bed, are acceptable in terms of fixing bacteria, especially methanogens, by including micronized supports of silicates or plastics of different densities, highlighting among them the system known as that of fluid bed reactor or expanded bed, where the performance of anaerobic digestion is increased, improving the adequacy of digester volumes.

Likewise, it achieves a reduction in the concentration of carbon dioxide in the reactor liquid, simplifying the temperature control in the process through the use of easily fluidized supports, reducing electrical consumption and favoring the development and selection of bacteria as a function of water residual to treat. This type of systems is widely used in the beer industry.

Also the anaerobic filters that improve, depending on the support used, the fixation of bacteria, creating a film around the spheres or balls, rings, built by plastics of different densities and configured inside the tanks randomly or modularly, being able to be fed with vertical flow (up-flow AF or down-flow DSFF). There are also two-phase reactors in which in a single expanded bed reactor the hydrolytic phase operated by a DSFF reactor and methane-gene are joined, this set constituting a high-speed reactor that considerably reduces the hydraulic residence time, and the habitat of the bacteria, reaching good rates of performance and efficiency.

Likewise, the works of IZA, COLLERAN and others can be commented on and are significant.

In Spain FIESTAS J. A. developed anaerobic reactors for the purification of industrial and urban wastewater, in 1996.

In any case, any of the systems mentioned have the disadvantage of not having resolved the maximum elimination of nitrogen in the hydrolytic phase and the subsequent elimination of the remaining nitrogen in the methanogenic phase, as well as the good fluidization of the silicates used for bacteria fixation

However, the applicant has protected systems in corresponding patents in which the habitat for the compatibility of bacteria is resolved, solving the stabilization of the pH from the hydrolytic digester, although based on the support used the points previously mentioned remain unresolved.

DESCRIPTION OF THE INVENTION

The equipment for biological purification of wastewater object of the invention, solves the problems referred to in the previous section, achieving a substantial improvement in the reduction of hydraulic residence times, as well as the purification capacity for high organic loads, with a maximum reduction of ammoniacal nitrogen and a reduction in cost economic, to include a single digester, with the consequent decrease of components, such as pumps, valves, heat exchangers, etc.

More specifically, the equipment of the invention is configured as a multiple anaerobic digestion equipment for the biological purification of wastewater with anaerobic hydrolytic and methanogenic digestion, resolving the incompatibility between bacteria, optimizing the different ecological niches in the same reactor and improving pH stability in the hydrolytic phase, by means of a new substrate used; as is the calcined atapuljita mixed with clays that contain in its chemical composition sepiolite so that they can be kneaded, then form rectangular pieces shaped like ceramic vaults that are normally used in the construction, so that the placement of these pieces in the The digester corresponds to a distribution in square or rectangular form, preventing the clogging of the channels through which the water circulates, determining sufficient contact surface for the fixation of bacteria between 6 and 10 square meters of surface for each cubic meter of inlet water . Preferably, the height of the ascending channels is fixed at a minimum of two and a half meters high.

The size of the reactor or digester of the equipment of the invention is defined by the sum of the hydraulic retention times of the different phases and according to the growth or better life time of the bacteria than for the hydrolytic, acid-gene and fermentative bacteria is of three days and for methano-genetics it is thirty hours. The feeding of said digester is carried out at the bottom with a conduit or tube, forming a distribution ring inside the digester to proportionally distribute the incoming flow through all the ascending channels that form the ceramic placed inside, the effluent being driven inwards by a mono-type, or rotor and stator variable flow pump.

The water that exits at the top of the digester, through a tompson channel, falls into a chamber or perimeter or outer compartment of the digester, from which that water is sent by means of a variable flow pump, through the corresponding duct, to the lower part of the commented perimeter compartment, in which bottom and externally a distribution ring with some entrances to the compartment is located, establishing in each of the entrances a venturi nozzle for a good expansion of the silicate inside the commented compartment, with the particularity that it is isolated from the inside of the digester and is in communication only with a gas storage hood established above, whose communication between compartment and gas storage bell is carried out by means of tubes that communicate the said part upper compartment or chamber with the repeated hood of accumulation of g ace.

On the other hand, a circular opening that extends upwards according to a cylindrical configuration is provided in the upper part of the mentioned bell, concentrically to which and externally there is another cylindrical neck, and between both cylinders a bell is arranged as an inverted bowl whose side and circular wall is arranged between the two cylinders mentioned, a bowl that has a hole in which a conduit for the gas outlet is connected, establishing a water tight seal between the two commented concentric and upper necks with the inverted bowl housed inside and between them.

The digester assembly is further complemented by opening and closing valves, as well as level probes, a diffuser ring in correspondence with the upper part and externally to the ceramic core, and a conical bottom bottom with a sludge discharge outlet.

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of drawings is attached as an integral part of said description. In an illustrative and non-limiting manner, the following has been represented:

Figure 1 shows a simplified view and according to an elevation of the biological wastewater purification equipment with anaerobic digestion, object of the invention.

Figure 2.- Shows a sectional view corresponding to the cutting line A-A of the previous figure.

PREFERRED EMBODIMENT OF THE INVENTION

As you can see in the referred figures, the team of Biological cleansing object of the invention presents the general shape of a cylindrical body by configuring a single digester with two concentric walls, one exterior (1) and another interior (2), being superiorly shaped, as an extension of the exterior wall (1), a closing bell (3), and as a lower closure, in correspondence with the inner wall (2), a lower closing bell (4), both bells (3) and (4) being conical configuration.

Between the concentric walls (1) and (2) of the digester, a chamber (5) extended inferiorly is established in a compartment (6), closed by the lower part according to a conical configuration (7).

In the inner body established by the wall (2) a block of ceramic pieces (8) is arranged, these having a vault shape, with a quadrangular or rectangular arrangement as shown in Figure 2, the set of ceramic pieces being (8 ) supported by joists (9), below which and at a certain distance from them, a distributor ring (10) is provided and in correspondence with the general inlet duct (11), all in such a way that by A pump impeller or any other system, the water to be treated is passed upwards through the ceramic assembly (8), to produce the corresponding aerobic process.

Centrally, the upper closing bell (3) has an opening delimited by a cylindrical neck (12), which is complemented by another outer and concentric (13), and between them a kind of inverted bowl (14) whose upper base is connected to a gas outlet conduit (15), in which a shut-off valve (16) and the corresponding coupling flange are provided. Between the cylindrical necks (12) and (13) an annular channel is established that is filled with water, the inverted bowl (14) remaining inside and establishing in this upper part a hermetic seal.

That is to say, by means of the arrangement of the cylindrical and concentric necks (12) and (13), an annular channel or receptacle is determined that fills with water to cover with the inverted bowl (14), provided with a single outlet to which the conduit (15) is connected, determining a perfect hydraulic closure, being able to give the pressure that is required for the optimal growth of the bacteria, pressure that is regulated by arranging greater or lesser weight in the upper part of the inverted bowl (14), It can be considered as an optimal working pressure between 300 and 400 millimeters of water column.

For its part, the lower closing bell (4) has a central and lower outlet (17) as a decanter, to which a duct or tube (18) is connected, with a manual valve for sludge discharge, that is, of digested biosolids, which are mostly made up of non-biodegradable minerals.

As for the height of the ceramic pieces (8), which are arranged in layers as shown in Figure 2, it will be determined by the BOD of the water to be purified, taking into account that a square meter of surface of contact contains at least two to three kilograms of biomass or bacteria adhered to said surface, taking into account that each ceramic piece has a contact surface of two and a half square meters, supporting between five and seven kilograms of biomass or bacteria attached, each kilogram of bacteria that support the ceramic pieces will consume twice their weight in organic matter for their normal development and growth, thus defining the number of ceramic pieces (8) that make up the contact surface inside the digester.

The ceramics used in its chemical composition must contain at least 40% of attapuljita, and be as porous as possible, which will be given by the microscopic laminar structure where hydrolytic bacteria can be easily introduced and removed to eat and not dragged by the upstream current of the digester.

Likewise, to say that this type of ceramic influences the stabilization of the pH of the digester, so that the upward feed influences the best performance of the digester, improving the stabilization of the process and reducing the hydraulic retention time in the methanogenic phase .

Above all the ceramic pieces (8) there is a conduit or tube (19 ') provided in correspondence with the feed inlet conduit (19), in which a valve is provided, with the particularity that the conduit (19 ') goes outside the general body of the digester and connects to the distribution ring (10), so that through a pump (21) the effluent is recirculated, which has only passed through the ceramic assembly (8) and decanted by the distance that separates the inlet of that tube (19 ') from the upper outlet of the water towards the outside of the digester.

Above the block of ceramic pieces (8), a tompson channel (22) of overflow and exit of water to the inner part of the chamber (5) is placed, water that falls from a certain height, whose distance is controlled by a level probe (23), so that when it exceeds a preset level the corresponding PLC associated with the equipment orders the stop of the corresponding feed pump, all this in such a way that this distance is necessary to perform the degassing of the water and that this does not pass the part of the lower compartment (6) with high gas contents.

In the commented chamber (5) of the digester, it is where the hydrolytic and acid-gene phases are carried out, with the only limitation being the height of water fall, since the other variables (width and height) will be sized according to the water flow To try a day.

From the aforementioned chamber (5), water flows out of the bottom of the compartment (6) through the tube or conduit (24), said water being driven by a pump (25), all in such a way that in correspondence With the conical lower part (7) of the compartment (6) referred to, nozzles (27) are provided which produce a venturi effect and which are evenly separated from each other, that is to say equidistant in a circular contour corresponding to the tube (28). ) provided externally and inferiorly through which the water from the upper chamber (5) of the acid-gene hydrolytic digester is introduced, by impulsion of a variable flow feed pump that serves to fluidize the silicate and keep it in suspension, of so that the silicate used to fix bacteria in the digester must have a specific granulometry and a specific weight somewhat higher than that of water, while the atapuljita calcined ade More of these two qualities must have a fibrous molecular structure. Where the methanogenic bacteria are fixed, the colonization of the particles takes place, forming clusters and releasing the methane gas by synthesizing in their diet the organic matter.

In the upper part of the compartment (6), in which it is carried out The methanogenic digestion and in correspondence with the entire circular perimeter, tubes (29) are placed, equiangularly separated from each other, whose function is to serve as means for the extraction of the gas produced in the compartment (6) and to conduct it, for storage , to the upper part (30) determined by the upper bell (3).

In the tubes or conduits (19 ') and (24), in which the discharge pumps (21) and (25) are interleaved respectively, the corresponding manual and pneumatic valves (31) are provided, also being seen in the figure 1 temperature probes (32), water level signaling (33) and an outlet (34) for the methanogen, whose output is provided in the compartment (6), as well as a level probe (35) in it latest.

In the upper part (30) there is a level of contact that determines the maximum filling volume of the digester, being that level of contact connected to the corresponding operating PLC that orders the closing of the corresponding pneumatic valves and therefore the shutdown of the feeding pumps (21) and (25), both the input to the internal digester and the external digester.

As for the purified water or effluent, it will lower by gravity to the decanter (17) established in the lower part of the hood (4), which is a lamella decanter, with a hydraulic retention time that is determined according to the amount of solids containing the purified effluent and the decantation rate, so that said solids or sludges produced in the decantation are incorporated into the sludge inlet or recirculation circuit (19) of the hydrolytic digester by means of a mono-type pump, connected by the bottom of the decanter, leading them to the feeding pipe (19) of the digester to digest them again. These Biosolids are organic matter because they are largely formed by dead bacteria, serving as food for the bacteria fixed in the hydrolyte when introduced through the upper part of the fixation pieces, forming a downward and slow current that improves the growth of the biomass , thus being digested and becoming part of the biosolids that are extracted through the duct (17) of the decanter. In the upper part of the decanter a connection (20) is provided for clean water outlet.

As for the constitution of the digester referred to, the fiberglass, virilester, iron, stainless steel or even concrete can be used as material, the latter duly painted inside with epoxy resins.

The equipment is complemented by a tank (36) with a decanted water outlet (37), a sludge outlet (38) for recirculation through the feed line (19) and the inlet (39) of water to be decanted and which constitutes the metallogenic product from the outlet (34), with that tank (36) counting on baffles (40), as clearly shown in Figure 1.

It should be said that the digester as a whole is heated with thermal blanket or projected polyurethane throughout its outer perimeter to achieve the lowest heat loss from the outside and to maintain an optimum temperature for the growth of bacteria inside, temperature that It can be achieved by using external market heat exchangers.

The entire unit will be controlled by the PLC, which receives information on the levels, temperature, pH and Redox probes, Programming for pump shutdown and commissioning, valve opening and closing and temperature control.

Claims

R E I V I N D I C A C I O N E S

I ^a .- Equipment for biological purification of wastewater, which being planned to perform an anaerobic digestion hydrolytic, fermentative, gene-acid and methano-gene, constituting itself through a single digester, is characterized in that it comprises a general cylindrical body with an outer wall (1) and an interior wall (2), determining an internal part for the arrangement of ceramic pieces (8) through which the water to be treated flows upwards, with an inlet (11) that flows into diffusers (12) provided inferiorly to that block of ceramic pieces (8), with the particularity that between both walls (1) and (2) a chamber (5) with a lower compartment (6) where methanogenic digestion takes place; with the particularity that a duct or tube (19 ') associated with a diffuser ring (10') in communication with the feed inlet (19), through whose tube is provided superior to the block of ceramic pieces (8) or conduit (19 ') the water is recirculated to the diffusers (10) provided under the block of ceramic pieces (8), while between the perimeter chamber (5) and the bottom of the compartment (6) in which said chamber (5), a conduit or tube (24) is provided that communicates with a perimeter, external and inferior conduit (28), with small tubes that are finished off in internal nozzles (27) of the lower part (7) of the compartment (6), it being provided that both pumps (21) and (25) are inserted in both the duct (19 ') and the duct (24) to drive the effluent to the diffusers (10) located under the ceramic block (8), as to the bottom of the compartment (6); with the particularity in addition that in the upper part a water overflow channel (22) is included for the gravity fall towards the outer and perimeter chamber (5), in which gas outlet ducts (29) are provided, the evacuation being established outside through a conduit (15) provided on the top or upper base of an inverted bowl (14) located in an annular channel established between two cylindrical necks (12) and (13) provided in correspondence with an upper and central outlet of an upper closing bell (3).

2 .- Equipment for biological treatment of wastewater according to claim Ia, wherein between the concentric collars (12) and (13) established in the upper chamber opening (30) determined by the hood top closure (3 ), a tight seal is determined in combination with the inverted bowl (14), by filling the annular channel with water between said two concentric necks (12) and (13).

3 .- Equipment for biological treatment of waste water, according to previous claims, characterized in that the ceramic (8) pieces having a chemical composition containing attapulgite, at least 40%, and its microscopic structure laminar porous to facilitate the transfer of the hydrolytic bacteria without being dragged by the updraft through such ceramic pieces (8), with the particularity that the block that forms these, in a quadrangular or rectangular arrangement, is supported by a series of beams (9 ).

4 .- Equipment for biological treatment of waste water, according to previous claims, characterized in that the lower end of the digester body, specifically the inner concentric cylindrical body is materialized by a hood (4) with an outlet (17) sludge decantation, for evacuation, through a conduit (18), to the outside. 5 .- Equipment for biological treatment of waste water, according to previous claims, characterized in that the conduits in the set include corresponding valves (31), manual and air, while the equipment includes level gauges (23) and (35) and a methano-gene outlet (34) and temperature probes (32).

6 ^a. - Equipment for biological purification of wastewater, according to previous claims, characterized in that the set is related to a PLC for control and control of all components and the correct functioning of the equipment.