WO2022064289A1

WO2022064289A1 - Biosolid biotransformation process using beetle larvae

Info

Publication number: WO2022064289A1
Application number: PCT/IB2021/057230
Authority: WO
Inventors: Luz Ángela Cuellar Rodríguez; Brigid Hiomara Pacheco García; Pedro Mauricio Acosta Castellanos
Original assignee: Universidad Santo Tomás Seccional Tunja
Priority date: 2020-09-24
Filing date: 2021-08-05
Publication date: 2022-03-31
Also published as: CO2020011872A1

Abstract

The process of biotransforming biosolids using beetle larvae belongs to the area of chemistry related to waste-based fertilisers, specifically to those fertilisers whose preparation is characterised by an industrial compost preparation step. The invention relates to a process stemming from the experimental results of a composting and biotransformation process using beetle larvae in compost heaps as an alternative to the management and disposal of biosolids, intended to prevent these wastes from being toxic or hazardous so they can be used as fertiliser or to restore soils.

Description

BIOSOLID BIOTRANSFORMATION PROCESS FROM BEETLE LARVAE

TECHNOLOGICAL SECTOR

The present invention belongs to the area of chemistry in relation to fertilizers from waste or waste, specifically those fertilizers where their preparation is characterized by the stage of industrial preparation of the compost. A process is presented that comes from the experimental results of a composting and biotransformation process with beetle larvae in composting piles as an alternative for the management and disposal of biosolids that intends that these residues stop being toxic or dangerous so that they can be used. as fertilizer or to restore soils.

STATE OF THE ART

In the state of the art, patent document No. CN1099383C "Effluent treatment system", dated January 22, 2003 and whose owner is Cameron DO, is known, which describes a treatment system for liquid or liquid and solid effluents . The system is enclosed within a pipe, conduit (10) or trench and comprises one or more inclined filter beds (12, 13, 14) with a population of effluent spoilage organisms such as earthworms and earthflies, and an overlying air space. The aqueous medium effluent inlet (1 1) is located above the upper filter bed at an upper end and the solid waste inlet (31), (when included), is located downstream of the medium inlet. aqueous medium for the aqueous medium to flow through and around the solid waste material. A filtrate outlet (28) is located downstream of the flow through the system and manual or conveyor means are provided for solids removal. In the new invention larvae of beetles are applied; Carabid beetles (Carabidae) are one of the large families of coprophagous beetles, which are responsible for carrying out the biotransformation of the material.

On the other hand, there is the patent document No. U20110271725A1 "Organic waste treatment system that uses verm ¡corrí postaje", dated November 10, 2011 and whose owner is Thomas E. Herlihy, provides a method of processing organic organic waste that includes aerobic conditioning, in a predominantly thermophilic regime lasting at least 72 hours, a mixture of organic wastes having a carbon to nitrogen ratio between about 15 to 1 to 45 to 1 to form a feedstock, applying the feedstock to a worm bed; and maintains a temperature and humidity of the worm bed and the applied feedstock to maintain a dominant mesophilic regime within the worm bed. This background comprises the steps of: (a) conditioning a mixture of organic wastes having a carbon/nitrogen ratio between about 10 to 1 to 60 to 1 to form a feedstock by suppressing anaerobic conditioning while maintaining dominant aerobic conditioning, in a predominantly thermophilic regimen lasting at least 72 hours; and (b) applying the feedstock to a worm bed. It further comprises maintaining a temperature and humidity of the worm bed and the applied feedstock to maintain a dominant mesophilic regime within the worm bed. In the new invention coprophagous beetle larvae are used, in addition, not only thermophilic microorganisms are used, mesophilic microorganisms are also used.

There is also patent document No. US7850848B2 "Devices and processes for the biological treatment of wastewater" dated September 17, 2009, whose owner is Christopher A. Limcaco. This background relates to a wastewater treatment facility comprising: a primary system with an inlet flow path to receive wastewater from a source; a first tank for containing wastewater received through an inflow path; a plurality of wheels in said first tank for rotation within the wastewater each containing a colony of bacteria capable of digesting organic carbon in the wastewater and respiring CO2, and each of the wheels includes surfaces to support growth of algae, where said surfaces are arranged to be alternately submerged in the sewage and exposed to sunlight; an air supply disposed within said first tank having a plurality of outlets directed to a corresponding plurality of wheels for rotating said wheels within the waste water and operable to aerate the waste water; and a primary outlet for discharging the effluent treated by said primary system after contact with bacteria and algae; a secondary treatment system with a second tank to receive the effluent discharged from the outlet of the primary system; a plurality of identical wheels configured with the wheels of the primary system; an air supply disposed within said second tank and configured with the air supply of the primary treatment system; and a secondary outlet for the discharge of the effluent treated by said secondary system after contact with the bacteria and algae. In the new invention, aerobic and anaerobic processes are carried out in the initial treatment with composting, tanks are not required, since the formation of aerobic piles is carried out for the composting stages and it is finished with the application of dung beetle larvae.

Finally, there is patent application No. W02005051853A1 "Alkaline stabilization of residual sludge in closed systems with optional ammonia recirculation" dated June 9, 2005 and whose owners are Blanca Elena Jiménez Cisneros, Juan Manuel Méndez Contreras. This background describes a process of alkaline stabilization of residual sludge in closed systems with optional ammonia recirculation that produces biosolids with limitations of pathogenic microorganisms that, due to their characteristics, are ideal for their application in soils for soil improvement, remediation of contaminated soils, generation of soils in infertile areas, intermediate cover of sanitary landfills and embankments without causing health and environmental problems. An optimization of the same process is the use of ammonia as a by-product that can be recovered and recirculated to the system to optimize its high disinfectant power or to market it due to its various industrial uses. The recirculation of ammonia to the process increases the nutrient content, so the affected sludge is specific for agricultural activities; In addition, the mass of the sludge is reduced by requiring less alkaline material, which reduces operating costs, as well as those of transporting biosolids. The new invention does not require the recirculation of ammonia, since in the system there are natural reactions, without the entry of any reagent, the stabilization process is carried out by the microbial action of temperature generated by the same reactions and the biological action of the digestive tract of dung beetle larvae.

DESCRIPTION OF THE INVENTION The attached figure illustrates the proposed scope of the invention within the following proposal for the process of biotransformation of biosolids from beetle larvae

Figure 1 shows the flowchart of the developed methodology.

Figure 2 shows the dimensioning of the composting pile.

Figure 3 shows the typical evolution of temperature in the composting stage.

Figure 4 shows the behavior of the pH in the composting of batteries 1 and 2.

Figure 5 shows the behavior of the temperature in the composting of pile 3.

Figure 6 presents the biotransformation process with larvae.

Figure 7 presents the phosphorus levels in the sampling stage.

In this document it is desired to capture the process of biotransformation of biosolids from beetle larvae from the process described by the following stages:

In the first stage, the process called composting is carried out, which includes the stabilization of organic matter through its aerobic degradation by the action of a controlled increase in temperature; Organic fertilizer is generated from microorganisms that act based on the air. The process takes place in a persistent degradation space for a maturation space that is distinguished in four phases: mesophilic, thermophilic, cooling and maturation.

Composting refers to a biooxidative process under controlled conditions that includes the addition of a substrate material with heterogeneous organic characteristics in a solid state. Compared to other processes, controlled biooxidation guarantees better efficiency since it is quite effective in reducing pathogens, suppressing bad odors and reducing the period required to stabilize the material.

The mesophilic phase in the composting process is characterized by reaching high temperatures of up to 45 ^S C, it begins with the formation of microorganisms called mesophiles that give way to the decomposition of molecules that have a greater facility for degradation. In this phase of the process, energy is released triggers in the increase of the temperatures of the treated material, as well as in the decrease of the pH.

During the thermophilic phase, the pH tends towards alkalinity, the number of mesophilic microorganisms decreases, giving rise to the formation of thermophilic microorganisms, also continuing with the gradual increase in temperatures. Thanks to the high temperatures that can reach 70 ^s C, the elimination of pathogenic microorganisms is achieved as well as easily degradable substances such as sugars, fats, starches and proteins. The thermophilic phase ensures the sanitization or sterilization of the material, since by eliminating pathogens it also ensures that they do not proliferate again in the maturation phase. These two phases can take from days to months, depending on the volume and type of material, in addition to the local climate, among others; Likewise, they must be carried out in suitable settings so as not to compromise the maturation phase and improve the quality of the final product.

In the cooling phase, the temperatures drop again to 40 - 45 ^S C, degrading the cellulose as a polymer. With the appearance of fungi, the pH drops with a subtle tendency towards alkalinity and some mesophyll-type microorganisms reappear; it requires time because it tends to be confused with the maturation phase. The last phase is the maturation of the compost whose duration requires weeks to months at room temperature, in which secondary reactions are carried out that give rise to humic and fulvic acids, microbial activity is reduced and the pH continues to be slightly alkaline.

In the second stage, the physical chemical characterization of the biosolid is carried out, where the biosolid is sampled. This characterization process is applied both throughout the composting process and during the biotransformation, which involves taking different samples.

The physicochemical characterization of the material to be treated is essential for the study of the evolution of the composting process, since it allows evaluating different parameters that allow classifying the material according to its characteristics, granting alternatives of final use in soils. The third stage includes the elaboration of biosolid piles, where it was seen the need to elaborate small biosolid piles to guarantee the aeration of the compost, to determine the appropriate volume for the biotransformation process based on time, material characteristics and conditions. climatic conditions of the place, an approximate area of 50 m2 was required to locate 2 composting piles with a pyramidal structure.

The composting process is generally carried out in pyramidal-shaped piles, which refers to the third stage of sizing and assembly of piles, where the size of the piles and the frequency of turning is based on the type of material, however , a limitation is the height of the pile since the higher the height, the greater the probability of material compaction, reducing its porosity, making aeration difficult; therefore, studies suggest heights between 1.2 and 1.8 meters and widths between 2.4 and 3.6 meters. For the biosolids biotransformation process from beetle larvae, an approximate area of 50 m2 is used to locate 2 composting piles with a pyramidal structure with a base width of 1.7 meters, a crown width of 0. 5 meters and a height of 1.0 meters to complete an approximate volume of 1.57 m3 per stack.

Then, as a fourth stage, there is the stabilization of the substrate, where the normalization of pH, humidity and temperature conditions is carried out, the integration of the structuring material is carried out, also known as support material or amendment material, which is a essential aspect to provide optimal conditions in the composting process. The purpose of adding the structuring material is to optimize the process in terms of aeration and nutrient content to improve the quality of the final product.

The size of the particles of the material to be composted is essential in the process since the greater the space exposed to the operation of the microorganisms, the faster and more complete the reaction. The speed of the process is maximized in a ground material, however, although this would cause a large contact surface for microbial work, it would also restrict the volume between particles, increasing the frictional force and limiting the diffusion of oxygen into the interior of the material. the piles giving way to a collapse of aerobic microorganisms by making aeration by natural convection impossible.

Taking into account the physical characteristics of the biosolid from its high moisture content that favors clogging scenarios and hinders an aerobic process, it is necessary to stabilize the biosolid substrate with a support material such as sugar cane bagasse. The foregoing, in addition to favoring the manageability conditions of the material at the time of turning and promoting an optimal scenario at the time of the application of the beetle larvae.

The starting point of the dosage is due to experimental situations of composting in other studies where it is shown that to compost sludge from urban wastewater treatment plants, different volumetric ratios are used that are mainly based on the moisture content of the sludge. , being able to establish as extreme values of 1/1 to 4/1 of structuring material/sludge, in the case of mechanically dehydrated sewage sludge, volumetric mixing ratios of 2/1 to 3/1 of structuring material/ mud.

Due to the characteristics of the biosolid, where, due to its humidity and viscosity, it lacks manageability and also hinders the aerobic conditions of the process, the following proportion is defined for each pile: 40% support material (structuring) and 60% biosolid.

To obtain a homogeneous mixture of the material, it is necessary to assemble each composting pile in layers of 0.20 meters, guaranteeing the pyramidal structure and the volumetric percentage of its components. In this phase of the investigation, some environmental aspects are premised, such as direct infiltrations into the soil or by runoff and the spread of vectors; Therefore, preventive measures must be taken, such as the installation of 6-gauge plastic at the base of the piles, the installation of a tent that protects the material from precipitation, the preparation of ditches around the assembly to control runoff, and the location of the Experimental montage away from vector sources. The next stage, called biotransformation of the material, corresponds to the inclusion of organisms such as beetles, beetles and larvae.

One of the main biotransformation processes that can be used in the management of biosolids is the use of beetle larvae, since their chewing mouthparts and the polyphagous feeding of these organisms facilitate the transformation of the waste into biofertilizer. Beetles, from the larval stage, carry out the work of biotransformation of organic matter, providing organic colloids and supplying essential nutrients for plant growth.

The biotransformation of beetle larvae is incorporated into the process, aiming at the generation of a biofertilizer whose characteristics are in accordance with current regulations. Organic fertilizer as a soil conditioner favors the availability of stable components and the capture of nutrients through the carbon, nitrogen and phosphorus cycle.

The beetle larvae are arranged in the piles at room temperature during the maturation phase, considering that the condition of the material at the time of application of the larvae is of low toxicity. During this cycle, the larvae carry out their feeding process with the ability to carry out movements in the treated biosolids, aerating and allowing the growth of bacteria in it that can become beneficial in soils.

After the 19 weeks of the composting process of the pile, the biotransformation stage of the material begins through two bioassays in the laboratory with sterilized containers, which incorporate the sample of the material taken in the field. In search of finding the optimal conditions for the process, it is decided that each bioassay contains material in specific granulometric conditions, in order to evaluate the behavior of the variables, while comparing the physicochemical and microbiological results in each bioassay.

Bioassay 1 is formed with the material that passes sieve No. 4, being previously tamped to reduce the amount of material of large proportions (sugar cane bagasse), increasing the possibility that the resulting sample contains particles of the structuring material. The volume of this bioassay corresponds to 0.024 m3 and its weight is 12 kg. The temperature of the material at the end of the assembly is 17.8°C, with a pH of 5.6 and a humidity percentage of 79.1%.

Once the material is arranged in the container and with the desired granulometry, the physical variables are taken and the beetle larvae are subsequently incorporated to complete the bioassay. In this way, 35 larvae of different sizes (35 to 40 cm in length) are added uniformly within the bioassay, which give way to the beginning of the biotransformation process of the material.

If an accelerated biotransformation process is desired, a high density of larvae is required, for which bioassays of 12 kg each were formed; When calculating the ratio of the content of larvae that each one should have, an amount of 5 larvae was estimated for each bioassay. However, due to the physicochemical and microbiological characteristics of the material, the decision was made to use 7 times the amount deducted, for a total of 35 larvae per bioassay in order to speed up the process and optimize its results. The surface area of the bioassay corresponds to 0.12 m2, so it was estimated that each larva would occupy a space of 34 cm2 at a depth of 20 cm. The larvae are uniformly deposited on the surface of each bioassay, taking into account that they are living organisms with their own movement, they move quickly into the composted biosolid mass, and thus remain in motion throughout the process. process.

The beetle larvae may be native species and are placed in the piles at room temperature during the maturation phase, considering that the condition of the material at the time of application of the larvae is of low toxicity. During this cycle, the larvae carry out their feeding process with the ability to make movements in the biosolid.

The experimentation during the biotransformation process takes place for 8 weeks, in which the variables of pH, temperature and humidity are monitored in order to evaluate their behavior and evolution. This stage is called start-up and monitoring, where the verification of physicochemical variables and development of the process is carried out by measuring variables such as pH, temperature, metals, granulometry, among others. Some of these values were obtained in the field, while others were obtained through sampling and characterization in the laboratory.

The pH in the bioassay made with bagasse shows a constant behavior with a tendency to neutrality, throughout the biotransformation, starting at 5.53 pH units and ending at 7.0 pH units. At the same time, the pH in the bioassay made with the sieved sample fluctuates between 5.18 pH units and 6.6 pH units, registering a value of 6.0 pH units at the end of the biotransformation.

The total nitrogen shows a decrease between the raw and composted biosolid from 5.68 g/100g to 2.69 g/100g, whose trend continues in the biotransformation with larvae in the sieved sample with 1.58 g/100g of total nitrogen, but it is maintained with a brief inclination to increase in biotransformation with larvae and sugarcane bagasse with a value of 2.94g/100g. The total organic carbon for its part, although it has a decrease of almost 50% between the raw biosolid and the composted one, is recovered during the biotransformation in the two bioassays. Knowing that this parameter works as a source of energy in the heterotrophs present in the soil, its effects on the chemical, physical and biological properties in the soil imply an important factor in their productivity. For this reason, the increase in the parameter demonstrates favorable conditions in the final product.

The C/N, C/P and N/P ratios are essential to know the benefits of composting, as well as the final product. The C/N ratio in the raw material starts from 5.28 and increases to 7.14 after the composting process, having a value far from the optimum suggested within organic waste composting, which has been estimated at 25 to 35, taking into account that microorganisms absorb between 15 and 30 carbon fractions for one nitrogen fraction. However, during biotransformation with beetle larvae, an increase in the parameter is observed, considering a value close to the optimum for a mature compost estimated at 10, in the bioassay that contains the larvae and the sugar cane bagasse with a ratio of 12.76. Specifying that the C/P ratio for organic waste composting is recommended between 75 and 150, it is shown in the results that the C/P ratio is 1 12.

Although the C/P ratio shows an increase between the raw material and the composted material, this result does not reach the limits mentioned; on the contrary, during the biotransformation of the material it can be seen that in the bioassay containing beetle larvae and sugarcane bagasse of sugar, this parameter reaches a value of 77.67, adjusting to the range suggested above. The N/P ratio shows a decrease throughout the experimentation, observing favorable results according to the limits set, with a value of 8.16 in the composted material, and a value of 6.09 in the biotransformation with larvae of beetle and sugarcane bagasse.

According to the microbiological characterization, the following results are obtained by the counting method: for the crude biosolid 4.08+06 CFU/G of total coliforms, presence of helminth eggs, presence of salmonella Sp and 75 PFU/4 g weight dried seaweed; for the composted biosolid 2.15+06 CFU/G of total coliforms, absence of helminth eggs, absence of salmonella Sp and 38.5 PFU/4 g dry weight of algae; for the sieved biotransformed biosolid 1.08+06 CFU/G of total coliforms, absence of helminth eggs, absence of salmonella Sp and absence of algae; and for the biosolid biotransformed with bagasse 1.08+06 CFU/G of total coliforms, absence of helminth eggs, absence of salmonella Sp and absence of algae.

The monitoring of heavy metals in the material allows determining the efficiency of the composting and biotransformation process in 6 of the 10 metals evaluated, corresponding to arsenic, copper, mercury, molybdenum, selenium and zinc.

The arsenic and selenium present in the material at the beginning of the process are maintained after composting, however, during the biotransformation of the material, a reduction of them is observed, in fairly similar proportions in each bioassay. On the other hand, copper, molybdenum and zinc respond to a decrease in the composting stage, which is maintained in the biotransformation of the material within the two bioassays.

Mercury, for its part, shows a decrease during the composting stage, which continues throughout the biotransformation, noting better removal results in the bioassay that contains the sample with sugar cane bagasse.

According to the characterization of heavy metals by the atomic absorption method, the following results are obtained: for the crude biosolid, 3.88 mg of mercury on 1 kg of biosolid; 1.67 mg molybdenum per 1 kg biosolid, <0.1 mg nickel per 1 kg biosolid, <5 mg selenium per 1 kg biosolid, <0.3 mg lead per 1 kg biosolid, 2 0.54 mg of zinc on 1 kg of biosolid, <5 mg of arsenic on 1 kg of biosolid, <0.05 mg of cadmium on 1 kg of biosolid, <0.05 mg of chromium on 1 kg of biosolid and 0. 24 mg of copper on 1 kg of biosolid; for the composted biosolid 2.16 mg of mercury on 1 kg of biosolid; 0.72 mg molybdenum per 1 kg biosolid, <0.1 mg nickel per 1 kg biosolid, <5 mg selenium per 1 kg biosolid, <0.3 mg lead per 1 kg biosolid, 0 0.68 mg of zinc per 1 kg of biosolid, <5 mg of arsenic per 1 kg of biosolid, <0.05 mg of cadmium per 1 kg of biosolid, <0.05 mg of chromium per 1 kg of biosolid and <0 0.1 mg of copper on 1 kg of biosolid; for the screened biotransformed biosolid 1.98 mg of mercury on 1 kg of biosolid; 0.66 mg molybdenum per 1 kg biosolid, <0.1 mg nickel per 1 kg biosolid, 2.56 mg selenium per 1 kg biosolid, <0.3 mg lead per 1 kg biosolid, 0.7 mg of zinc on 1 kg of biosolid, 3.63 mg of arsenic on 1 kg of biosolid, <0.05 mg of cadmium on 1 kg of biosolid, <0.05 mg of chromium on 1 kg of biosolid and <0.1 mg of copper on 1 kg of biosolid; for the biosolid biotransformed with bagasse, 1.05 mg of mercury on 1 kg of biosolid; 0.67 mg molybdenum per 1 kg biosolid, <0.1 mg nickel per 1 kg biosolid, 2.62 mg selenium per 1 kg biosolid, <0.3 mg lead per 1 kg biosolid, 0.69 mg of zinc per 1 kg of biosolid, 3.56 mg of arsenic per 1 kg of biosolid, <0.05 mg of cadmium per 1 kg of biosolid, <0.05 mg of chromium per 1 kg of biosolid and <0.1 mg of copper on 1 kg of biosolid.

The importance of analyzing the different metals or elements named above lies in the fact that each element contains its own characteristics and risks, because when talking about metals with high densities, they can become toxic, even at low concentrations; Thus, trace elements such as selenium are not considered metals, while arsenic has been called a metalloid, while copper, zinc, molybdenum and nickel are considered essential micronutrients for plants. Because these trace elements are generally found in nature, they do not have the property of being destroyed or degraded biologically, so they bioaccumulate, that is, they increase their concentration in living organisms or in different types of materials. According to this, it is estimated that the reduction of metals generated during the composting stage of the material is related to its migration towards the structuring material and its precipitation due to gravity in the experimental setup. Regarding the metals that were reduced in the biotransformation stage, it is important to mention that due to their bioaccumulative property, it is estimated that the action of the beetle larvae causes the content removed in the material to be accumulated in these organisms.

In addition to this, the due turning was carried out to stabilize values in case they were harmful and interfered with the circulation of air or other elements of the dynamics of the ecosystem. From the analysis of the physical, chemical and microbiological variables, it is determined that the best conditions in the biotransformation are achieved with the material sample that maintains the granulometric properties acquired in the composting, by the action of the structuring material, since it provides appropriate scenarios. for the aeration of the material, guaranteeing an aerobic process.

As a final stage there is the evaluation of the final product, where an analysis of variables obtained in the final process is carried out.

From the results obtained, a comparison was made with the regulations and it was found that the final product obtained after the experimental phase is classified according to the code of federal regulations for the use or disposal of sewage sludge 40 CFR 503 developed by the United States EPA, in a class B, which allows all land uses, except; lawns, home gardens, food crops, soils for grazing animals and soils with a high potential for public exposure, provided that the reduction of vector attraction is guaranteed.

According to the classification of the matter according to the contaminant with EPA 40 CFR 503, the final product has the following characteristics, for the composted biosolid <5 arsenic, <0.05 cadmium, <0.05 chromium, <0.1 copper, <0.3 lead, 2.16 mercury, 0.72 molybdenum, <0.1 nickel, <5 selenium, 0.68 zinc, 2.15+06 CFU/gram of biosolids in the limit of fecal coliforms, absence of salmonella and absence of viable helminth eggs; for the screened biotransformed biosolid 3.63 arsenic, <0.05 cadmium, <0.05 chromium, <0.1 copper, <0.3 lead, 1.98 mercury, 0.66 molybdenum , <0.1 nickel, 2.56 selenium, 0.7 zinc, 1.08+06 CFU/gram of biosolids at the limit of fecal coliforms, absence of salmonella and absence of viable helminth eggs and for the biosolid biotransformed with bagasse 3.56 arsenic, <0.05 cadmium, <0.05 chromium, <0.1 copper, <0.3 lead, 1.05 mercury, 0.67 molybdenum, <0.1 nickel, 2.62 selenium, 0.69 zinc, 1.01 +06 CFU/gram of biosolids at the limit of fecal coliforms, absence of salmonella and absence of viable helminth eggs.

In this way, it is possible to interpret that the material after composting does not comply with either of the two classes in the fecal coliform parameter; however, the material after the biotransformation has been carried out, if it complies with the Class B of biosolid in the same parameter. Regarding the other parameters related to salmonella and helminth eggs, the compliance of the material is denoted from the moment in which the composting is carried out, taking as a premise that the limits in these parameters are established only for the class A biosolid.

The material at the end of the experimentation complies as class B within the contaminant concentration option (PC) and also within the accumulative contaminant load rate option (CPLR) which can be used in all land uses except lawns and home gardens, food crops, soils for grazing animals, and soils with high potential for public exposure.

The evaluation of the biotransformation process of biosolids extracted from the wastewater treatment plant, allows to determine that from a stabilization of the biosolid with a support material within a composting process; the addition of beetle larvae is a viable alternative to improve the microbiological and physicochemical properties of the final product.

Claims

1. Biosolids biotransformation process from beetle larvae CHARACTERIZED by the following stages:

(a) Compost and stabilize organic matter through controlled temperature increases, which are between 45°C - 70°C;

(b) physical and chemical characterization of the biosolid through sampling,

(c) sizing and assembling the biosolid where two pyramidal structure composting piles were made with a base width of 1.7 m, a crown width of 0.5 m and a height of 1.0 m to complete a approximate volume of 1.57 m3 per pile, and an assembly of each composting pile in layers of 0.20 meters guaranteeing the pyramidal structure,

(d) stabilize the substrate by adding the structuring material sugarcane bagasse in the following proportion for each pile: 40% support material (structuring) and 60% biosolid,

(e) adding organisms such beetles, beetles and larvae to carry out the biotransformation stage, two bioassays are used in the laboratory with sterilized containers, which incorporate the sample of the material taken in the field, where bioassay 1 is made with the material that it passes the N°4 sieve, being previously tamped to reduce the amount of material of large proportions (sugar cane bagasse). The volume of this bioassay corresponds to 0.024 m3 and its weight is 12 kg. The temperature of the material at the end of the assembly is 17.8°C, with a pH of 5.6 and a humidity percentage of 79.1%. Once the material is ready for the bioassay, physical variables are taken and subsequent incorporation of the beetle larvae to complete the bioassay. In this way, 35 larvae of different sizes (35 to 40 cm in length) are added uniformly within the bioassay,

(f) verify physicochemical variables through the measurement of variables such as pH, temperature, metals, granulometry, among others. In addition to this, the due turning is carried out to stabilize values in case they are harmful and interfere with the circulation of air or other elements of the dynamics of the ecosystem,

(g) Evaluate the final product through the analysis of variables obtained, where the final product is classified for the use or disposal of water sludge waste that allows all land uses, except; lawns, home gardens, food crops, land for grazing animals and land with a high potential for public exposure, provided that the reduction of vector attraction is guaranteed.

2. Process for the biotransformation of biosolids from beetle larvae according to claim 1, characterized in that the beetle larvae are placed in the piles at room temperature during the maturation phase.

3. Process for the biotransformation of biosolids from beetle larvae according to claim 1, characterized in that the surface area of the bioassay corresponds to 0.12 m2, where each larva occupies a space of 34 cm2 at a depth of 20 cm, the which are deposited on the surface of each bioassay in a uniform manner.

4. Process for the biotransformation of biosolids from beetle larvae according to claim 1, characterized in that the experimentation during the biotransformation stage takes place for 8 weeks, in which the variables of pH, temperature and humidity with the purpose of evaluating its behavior and evolution.

5. Process for the biotransformation of biosolids from beetle larvae according to claim 1, characterized in that the pH in the bioassay made with bagasse shows a constant behavior with a tendency to neutrality, throughout the biotransformation, starting from 5, 53 pH units and ending at 7.0 pH units. At the same time, the pH in the bioassay made with the sieved sample fluctuates between 5.18 pH units and 6.6 pH units, registering a value of 6.0 pH units at the end of the biotransformation.

6. Process for the biotransformation of biosolids from beetle larvae according to claim 1, characterized in that according to the microbiological characterization, the following results are obtained by the counting method: for the crude biosolid 4.08+06 CFU/G of total coliforms, presence of helminth eggs, presence of salmonella Sp and 75 PFU/4 g dry weight of algae; for the composted biosolid 2.15+06 CFU/G of total coliforms, absence of helminth eggs, absence of salmonella Sp and 38.5 PFU/4 g dry weight of algae; for the sifted biotransformed biosolid 1.08+06 CFU/G of total coliforms, absence of helminth eggs, absence of salmonella Sp and 18 absence of algae; and for the biosolid biotransformed with bagasse 1.08+06 CFU/G of total coliforms, absence of helminth eggs, absence of salmonella Sp and absence of algae. Process of biotransformation of biosolids from beetle larvae according to claim 1, characterized in that according to the characterization of heavy metals by the atomic absorption method, the following results are obtained: for the crude biosolid 3.88 mg of mercury on 1 kg of biosolid; 1.67 mg molybdenum per 1 kg biosolid, <0.1 mg nickel per 1 kg biosolid, <5 mg selenium per 1 kg biosolid, <0.3 mg lead per 1 kg biosolid, 2 0.54 mg of zinc on 1 kg of biosolid, <5 mg of arsenic on 1 kg of biosolid, <0.05 mg of cadmium on 1 kg of biosolid, <0.05 mg of chromium on 1 kg of biosolid and 0. 24 mg of copper on 1 kg of biosolid; for the composted biosolid 2.16 mg of mercury on 1 kg of biosolid; 0.72 mg molybdenum per 1 kg biosolid, <0.1 mg nickel per 1 kg biosolid, <5 mg selenium per 1 kg biosolid, <0.3 mg lead per 1 kg biosolid, 0 0.68 mg of zinc per 1 kg of biosolid, <5 mg of arsenic per 1 kg of biosolid, <0.05 mg of cadmium per 1 kg of biosolid, <0.05 mg of chromium per 1 kg of biosolid and <0 0.1 mg of copper on 1 kg of biosolid; for the screened biotransformed biosolid 1.98 mg of mercury on 1 kg of biosolid; 0.66 mg molybdenum per 1 kg biosolid, <0.1 mg nickel per 1 kg biosolid, 2.56 mg selenium per 1 kg biosolid, <0.3 mg lead per 1 kg biosolid, 0.7 mg of zinc on 1 kg of biosolid, 3.63 mg of arsenic on 1 kg of biosolid, <0.05 mg of cadmium on 1 kg of biosolid, <0.05 mg of chromium on 1 kg of biosolid and <0.1 mg of copper on 1 kg of biosolid; for the biosolid biotransformed with bagasse, 1.05 mg of mercury on 1 kg of biosolid; 0.67 mg molybdenum per 1 kg biosolid, <0.1 mg nickel per 1 kg biosolid, 2.62 mg selenium per 1 kg biosolid, <0.3 mg lead per 1 kg biosolid, 0.69 mg of zinc per 1 kg of biosolid, 3.56 mg of arsenic per 1 kg of biosolid, <0.05 mg of cadmium per 1 kg of biosolid, <0.05 mg of chromium per 1 kg of biosolid and <0.1 mg of copper on 1 kg of biosolid. Final product obtained from the biosolids biotransformation process from beetle larvae characterized by presenting the following characteristics, for the composted biosolid <5 arsenic, <0.05 cadmium, <0.05 chromium, <0.1 copper, <0.3 lead, 2.16 mercury, 0.72 molybdenum, <0.1 nickel, 19

<5 of selenium, 0.68 of zinc, 2.15+06 CFU/gram of biosolids in the limit of fecal coliforms, absence of salmonella and absence of viable helminth eggs; for the screened biotransformed biosolid 3.63 arsenic, <0.05 cadmium, <0.05 chromium, <0.1 copper, <0.3 lead, 1.98 mercury, 0.66 molybdenum , <0.1 nickel, 2.56 selenium, 0.7 zinc, 1.08+06 CFU/gram of biosolids in the limit of fecal coliforms, absence of salmonella and absence of viable helminth eggs and for the biosolid biotransformed with bagasse 3.56 arsenic, <0.05 cadmium, <0.05 chromium, <0.1 copper, <0.3 lead, 1.05 mercury, 0.67 molybdenum, <0.1 nickel, 2.62 selenium, 0.69 zinc, 1.01 +06 CFU/gram of biosolids at the limit of fecal coliforms, absence of salmonella and absence of viable helminth eggs.