Poultry Slaughterhouse Wastewater Treatment Research Articles

Poultry Slaughterhouse Wastewater Treatment Using Submerged Fibers in an Attached Growth Sequential Batch Reactor.

In this study, a sequential batch reactor (SBR) with different types of fibers was employed for the treatment of poultry slaughterhouse wastewater. Three types of fibers, namely, juite fiber (JF), bio-fringe fiber (BF), and siliconised conjugated polyester fiber (SCPF), were used. Four SBR experiments were conducted, using the fibers in different reactors, while the fourth reactor used a combination of these fibers. The treatment efficiency of the different reactors with and without fibers on biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia-nitrogen (NH3-N), phosphorus (P), nitrite (NO2), nitrate (NO3), total suspended solids (TSS), and oil-grease were evaluated. The removal efficiency for the reactors with fibers was higher than that of the reactor without fibers for all pollutants. The treated effluent had 40 mg/L BOD5 and 45 mg/L COD with an average removal efficiency of 96% and 93%, respectively, which meet the discharge limits stated in the Environmental Quality Act in Malaysia.

Efficiency analysis of the electrocoagulation and electroflotation treatment of poultry slaughterhouse wastewater using aluminum and graphite anodes.

The application of electrocoagulation (EC) and electroflotation (EF) was investigated for the treatment of poultry slaughterhouse wastewater in a bench scale unit cell electrolyzer with different EC-to-EF ratios at current densities of 3, 9, and 15mAcm-2. The EC-to-EF ratio was controlled by current reversal using aluminum and graphite electrodes. The electrochemical treatment showed satisfactory removal efficiencies for Al coagulant loads greater than 51.8mgL-1. The 4/5 EC to EF ratio (69.1mgL-1 Al and 32.2NmLL-1 additional EF gas) and 3/5 (51.8mgL-1 Al/64NmLL-1 additional EF gas) presented the best results for the removal of COD (76-85%), color (93-99%), and turbidity (95-99%), with the additional benefit of reducing the electrode consumption and sludge disposal costs proportionally to the EC-to-EF ratio. The effects of the EC-to-EF ratio and the current density on efficiency of the electrochemical treatment for the removal of COD, apparent color, turbidity, TSS, TSD, and NH3-N were discussed in the light of the physicochemical and electrochemical processes underlying the removal mechanism for each parameter. In particular, the blow-off mechanism seems to play an important role in the NH3-N removal, whereas indirect electrooxidation mechanism accounts for a fraction of the soluble COD removal for the electrodes configuration used in the treatment.

Effect of incorporating sludge from poultry slaughterhouse wastewater treatment system in ceramic mass for tile production

Abstract Brazil is one of the largest producers of red ceramic in the world and the main mass used in the manufacture of this product are composed exclusively of clay, which are extremely abundant in the Earth’s crust. Several studies in the literature consider the incorporation of small amounts of waste from different segments in the ceramic mass, usually at levels lower than 10%, due to the inertness of waste by ceramic processing. The western region of the State of Parana stands out in the production and processing of poultry meat, and this process in the slaughterhouses industry consumes a lot of water, and consequently generates effluents that require a specific treatment. Normally, the wastewater treatment system used for this activity is the process of physical–chemical flotation followed by tridecanters, which generates a considerable amount of sludge that also needs a proper disposal; it is often sent to outsourced companies to produce compost along with other organic materials, but with a high cost of transportation and destination for generating companies. Given this fact, seeking viable alternatives to the use of this type of sludge generated in the poultry slaughterhouse wastewater treatment system, it was proposed a study to evaluate, on a laboratory scale, the technical feasibility of incorporating it in ceramic mass intended for manufacturing tiles. Low concentrations of sludge generated by the slaughterhouses have been included in a mass industrially used for the manufacture of ceramic tiles and the performance of the mixtures was evaluated compared to a reference mass, without inclusion of waste. The specimens prepared with such formulations were tested for bulk density, linear drying and firing shrinkage, bending rupture stress, efflorescence formation and the behavior of mixture during firing was evaluated by vitrification curves. The results indicate that incorporation of 2% (w / w) sludge in the ceramic mass did not significantly alter the properties of the material, being even possible to reduce the consumption of fuel in burning, since the inclusion of such organic matter into the mass contribute to heat generation, since the combustion of the material is an exothermic reaction.

Aerobic Methanotrophs Grew Under Anoxic Conditions and Supported a Diverse Heterotrophic Bacterial Community

Abstract Methanotrophy has become a promising process for biotechnological applications. The initial goal of this study was to investigate methanotrophic denitrification as an alternative to nitrogen removal in waters that have a low organic content. Sequencing batch reactors (SBRs) were inoculated with a blend of marine and mangrove sediments (Sed-SBR), or anaerobic granular sludge from a upflow anaerobic sludge bed reactor treating poultry slaughterhouse wastewater (AnS-SBR) immobilized in polyurethane foams under anoxic conditions. Methane was provided as the sole external electron donor and organic carbon source. Methane supported denitrification to a small extent (<2.0 mg N.g total volatile solids−1 d−1) and supported biomass growth for the AnS-SBR in 10% of the initial volatile suspended solids. DNA sequencing of initial inocula showed high richness and low dominance for Sed inoculum, while the most abundant microorganisms in AnS inoculum were chemoorganotrophs typically found in anaerobic environme...

Prospecting for sludge bacteria from a poultry slaughterhouse, with potential for degrading organic substances

The sludge produced in wastewater treatment plants of slaughterhouses is a rich source of chemical, organic, and microbiological constituents that can be biotechnologically exploited. The purpose of this study was to (i) conduct a chemical analysis of the sludge, and (ii) isolate, quantify, and describe the amylolytic, cellulolytic, ligninolytic, proteolytic, and keratinolytic bacteria in the sludge. Sludge samples were collected at the wastewater treatment plant of the Francap SA poultry company. The nutrient contents, C/N ratio, and pH were determined. For the bacterial count, 10 g sludge was diluted in 90 mL saline solution, which was serially diluted to 10-12. Aliquots of 100 µL of each dilution were transferred to selective media for isolation of bacteria that degrade organic substances. The colony-forming units were determined for each culture medium. Individual colonies were purified and characterized morphologically. The sludge contained 9.5, 1.21, and 0.45 dag kg-1 of N, P, and K, respectively. Fifty-two isolates were purified and characterized, with 2.11 × 1012 to 9.55 ×1015 colony-forming units per g sludge. In conclusion, the sludge generated in poultry slaughterhouse wastewater treatment plants is a rich source of organo-mineral constituents and bacteria with biotechnological potential for degrading organic substances.

Microbial diversity of a full-scale UASB reactor applied to poultry slaughterhouse wastewater treatment: integration of 16S rRNA gene amplicon and shotgun metagenomic sequencing.

The 16S rRNA gene amplicon and whole‐genome shotgun metagenomic (WGSM) sequencing approaches were used to investigate wide‐spectrum profiles of microbial composition and metabolic diversity from a full‐scale UASB reactor applied to poultry slaughterhouse wastewater treatment. The data were generated by using MiSeq 2 × 250 bp and HiSeq 2 × 150 bp Illumina sequencing platforms for 16S amplicon and WGSM sequencing, respectively. Each approach revealed a distinct microbial community profile, with Pseudomonas and Psychrobacter as predominant genus for the WGSM dataset and Clostridium and Methanosaeta for the 16S rRNA gene amplicon dataset. The virome characterization revealed the presence of two viral families with Bacteria and Archaea as host, Myoviridae, and Siphoviridae. A wide functional diversity was found with predominance of genes involved in the metabolism of acetone, butanol, and ethanol synthesis; and one‐carbon metabolism (e.g., methanogenesis). Genes related to the acetotrophic methanogenesis pathways were more abundant than methylotrophic and hydrogenotrophic, corroborating the taxonomic results that showed the prevalence of the acetotrophic genus Methanosaeta. Moreover, the dataset indicated a variety of metabolic genes involved in sulfur, nitrogen, iron, and phosphorus cycles, with many genera able to act in all cycles. BLAST analysis against Antibiotic Resistance Genes Database (ARDB) revealed that microbial community contained 43 different types of antibiotic resistance genes, some of them were associated with growth chicken promotion (e.g., bacitracin, tetracycline, and polymyxin).

Performance of integrated anaerobic/aerobic sequencing batch reactor treating poultry slaughterhouse wastewater

The present study investigates the performance of a new configuration laboratory-scale bioreactor comprising of two regimes (anaerobic & aerobic) in one reactor with physical separation and it is known as integrated anaerobic/aerobic sequencing batch reactor (IAASBR). The IAASBR is designed for treating high-strength wastewater such as poultry slaughterhouse wastewater (PSW) along with the simultaneous removal of organic carbon and ammoniacal nitrogen (NH3-N). The IAASBR exhibits that the average removal efficiency of total COD (TCOD), soluble COD (SCOD), NH3-N, fat, oil & grease (FOG), and total suspended solids (TSS) were (97%±2%), (95%±3%), (98%±1.3%), (90%±11%), and (96%±3%) respectively. The laboratory comparison test revealed that IAASBR configuration has enhanced the sludge settle-ability for aerobic SBR more than the conventional SBR or settling tank. Furthermore, IAASBR could tolerate the shock loading occurrence, handle organic loading rate (OLR) up to 4.5kg(TCOD)m−3d−1 and produce a high-quality effluent complying with Malaysian standards of industrial’s effluents.

Aeration Energy Requirements in Microalgal Heterotrophic Bioreactors Applied to Agroindustrial Wastewater Treatment

Background: The cultivation stage of a microalgae-based process has the highest energy burden, and a significant portion of this consumption is related to bioreactor aeration. Thus, the objective of this work was to assess the aeration energy requirements in heterotrophic microalgal bioreactors applied to poultry and swine slaughterhouse wastewater treatment. Methods: The experiments were performed in a bubble column bioreactor, operating at 25ºC, pH of 7.5, 100 mg/L of inoculum, absence of light and flow rate per unit volume (Q/V) of 0.5, 1.0 and 1.5 VVM (volume of air per volume of wastewater per minute). Based on this, experimental data estimated the aeration energy requirements and the net energy ratio of the system. Results: The results showed slight performance gains in cell growth and substrate consumption in flow rates per unit volume of 1.5 VVM. A markedly similar behavior was observed under the conditions of 0.5 and 1.0 VVM. Thus, Q/V of 0.5 VVM can be considered the equilibrium condition (kinetic performance vs energy consumption) for the operation of bioreactor. Conclusion: Based on experimental data, a power density of 9.68 W/m3 was estimated for the treatment of agroindustrial wastewater, resulting in a positive energy balance (NER>1). Keywords: Microalgae-based process, Phormidium autumnale, heterotrophic cultivation.

Performance of an expanded granular sludge bed (EGSB) reactor coupled with anoxic and aerobic bioreactors for treating poultry slaughterhouse wastewater

Generally, slaughterhouses have the largest consumption of fresh water and thus generate large quantities of high strength wastewater, which can be treated successfully using low cost biological treatment processes. In this study, the feasibility of using an expanded granular sludge bed (EGSB) anaerobic reactor coupled with anoxic and aerobic bioreactors for the treatment of poultry slaughterhouse wastewater was investigated. The poultry slaughterhouse was characterized by high chemical oxygen demand (COD), 2 to 6 g/L, with average biological oxygen demand of 2.4 g/L and average fats, oil and grease (FOG) being 0.55 g/L. A continuous EGSB anaerobic reactor was operated for 26 days at different hydraulic retention times (HRT), i.e. 7, 4, 3 days, and organic loading rates (OLR) of 0.5, 0.7 and 1.0 g COD/L.day, respectively, to assess the bioremediation of the poultry slaughterhouse wastewater. The average COD removal from the EGSB was 40%, 57% and 55% at the different OLR and HRT assessed. At high OLR of 1.0 g COD/L.day, the overall COD removal from the system (EGSB-anoxic/aerobic) averaged 65%. The system experienced periodical sludge washout during high FOG and suspended solids loading. It was concluded that the EGSB system requires a dissolved air flotation system, for FOG/suspended solid reduction, as the performance of the overall system was observed to deteriorate over time due to the presence of a high quantity of FOG including suspended solids.

Biological Treatment of Poultry Slaughterhouse Wastewater by Using Different Fibers

This study evaluated the performance of sequencing batch reactor (SBR) with and without the fibers of poultry slaughterhouse wastewater (PSWW). The fibers act as attachment materials to the suspended solids, which are considered as pollutant in PSWW. PSWW contains high-pollutant concentrations. Experiments were conducted using two 60 L laboratory SBR reactors at room temperature (25 °C) and pH 7±0.5. The removal percentage of SBR with and without the fibers was compared in terms of chemical oxygen demand and biological oxygen demand. The removal percentage of SBR with fibers showed higher overall performance, which was approximately 90%. Meanwhile, the removal of SBR without fibers achieved an average percentage of about 70%, which was slightly lower compared with SBR reactor with fibers.

Stabilization of Excess Sludge From Poultry Slaughterhouse Wastewater Treatment Plant by the Fenton Process

For stabilization of excess sludge in activated sludge process, the Fenton process was applied as a safe technique and its effectiveness was experimentally examined. In order to carry out experiments, a batch reactor with the effective volume of 0.5 L was used. Effect of hydraulic retention time, pH, H 2 O 2, and Fe concentrations on sludge stabilization were investigated. Before and after the process, the content of total solids (TS), volatile solid (VS), chemical oxygen demand (COD), and color were measured. The study showed that, the best efficiency was obtained when iron concentration was 60 mg/L, duration of the process was 150 minutes, pH = 3, and H 2 O 2 concentration was 4000 mg/L. The Fenton process can reduce the values of TS, VS, COD, and color to 50%, 61%, 53% and 61%, respectively. By analogy to conventional methods, the Fenton process is an effective method that can be suggested to stabilize excess sludge.

Treatment of poultry slaughterhouse wastewater using a membrane process, water reuse, and economic analysis

Poultry slaughterhouse wastewater, which represents one of the most important pollutants in Turkey, is generally treated with conventional biological processes in Turkey and around the world. In this study, poultry slaughterhouse wastewater was treated using laboratory-scale membrane processes, which were substituted for conventional processes. The performances of the membrane processes were investigated in terms of chemical oxygen demand (COD), conductivity, and membrane fluxes. Economic analyses were conducted for several membrane system alternatives. In addition, the alternatives were compared with each other and with conventional economic analysis of the data obtained in this study and data from several previous studies. The membranes used for the membrane processes were AG for reverse osmosis (RO), DK for nanofiltration (NF), and ER for ultrafiltration (UF). The highest COD removal efficiencies were 90% for NF and 97.4% for RO, and the conductivities decreased by 51.7% for NF and 96.6% for RO. When the (UF) was not used, the long-term membrane fluxes of the RO and (NF) sharply decreased, which increased the operation costs of these processes. Therefore, RO and NF without pre-treatment and with UF were not effective for this wastewater. According to the economic analysis results, the operational costs of the RO and NF after UF, the UF alone, and the conventional treatment process were 0.66, 0.70, 0.79, and 1.66 $/m3, respectively. Because the operational cost of the conventional treatment process was 2.5 times greater than RO after pre-treatment with UF, it was deduced that this membrane process combination was a suitable treatment alternative for treating poultry slaughterhouse wastewater.

The effect of initial pH on treatment of poultry slaughterhouse wastewater by electrocoagulation method

In this work, treatment of poultry slaughterhouse wastewater by electrocoagulation method with aluminum plate electrodes has been investigated. System was operated in batch and galvonostatic mode. Effect of initial pH of the wastewater was predominantly investigated on chemical oxygen demand (COD) removal efficiency but turbidity and oil–grease removal efficiencies were also evaluated. Operational parameters were kept constant at 150 rpm of stirring speed, 1 mA/cm2 of current density, and 293 K of solution temperature. On the other hand, initial pH of the wastewater was in the range of 2–8. Initial pH of the wastewater was an effective parameter on COD removal efficiency as it is expected. When initial pH of the wastewater was in the range from 3 to 4, it was possible to obtain higher COD removal rates. In this study, when the initial pH of wastewater equals to 3 and current density is 1 mA/cm2, system gives COD removal efficiency of 85% in 20 min. Meanwhile, system consumes 2.14 kWh/m3 of energy under above conditions.

Long-term performance and operational strategies of a poultry slaughterhouse waste stabilization pond system in a tropical climate

This paper discusses the performance of a poultry slaughterhouse wastewater treatment plant (WWTP) in a tropical country and operating strategies that were applied over 84 months to this WWTP. The WWTP consisted of a dissolved air flotation (DAF) system, anaerobic ponds (APs) and a facultative pond (FP). The organic loading rates applied to the APs ranged from 0.26 to 1.05kgBOD/m3day, and the hydraulic retention time ranged from 2.2 to 3.8days. The resultant COD and BOD removal efficiencies were 42±11% and 38±15%, respectively. The FP surface loading was up to 983kgBOD/haday. The main observed events in the WWTP processes over this period were organic overload, low chemical oxygen demand (COD) and biochemical oxygen demand (BOD) removal efficiencies and color change from green to reddish at the FP. Molecular biology techniques were used to identify microbial groups in the FP in the period of low organic matter removal efficiency and when the liquid became reddish. Sunny conditions favored anoxygenic photosynthesis, the growth of purple nonsulfur bacteria (such as Rhodocyclales-like organisms), and green nonsulfur bacteria (such as Chloroflexi-like organisms). Mechanical aeration at the inlet of the FP restored the water to its original color and increased the COD and BOD removal efficiencies. Based on the BOD removal efficiencies of 89%, after the installation of aerators, the operating strategies illustrate the WWTP system's capacity and versatility to adapt to load variations.

Assessment of a UASB reactor for the removal of sulfate from acid mine water

A bench-scale Upflow Anaerobic Sludge Blanket (UASB) reactor was used to study the treatment of acid mine drainage through the biological reduction of sulfate. The reactor was fed with acid mine drainage collected at the Osamu Utsumi uranium mine (Caldas, MG, Brazil) and supplemented with ethanol as an external carbon source. Anaerobic granular sludge originating from a reactor treating poultry slaughterhouse wastewater was used as the inoculum. The reactor's performance was studied according to variations in the chemical oxygen demand (COD)/SO42− ratio, influent dilution and liquid-phase recirculation. The digestion of a dilution of the acid mine drainage resulted in a 46.3% removal of the sulfate and an increase in the effluent pH (COD/SO42− = 0.67). An increase in the COD/SO42− ratio to 1.0 resulted in an 85.6% sulfate reduction. The reduction of sulfate through complete oxidation of the ethanol was the predominant path in the reactor, although the removal of COD was not greater than 68% in any of the operational stages. The replenishment of the liquid phase with tap water positively affected the reactor, whereas the recirculation of treated effluent caused disequilibrium and decreased efficiency.

Process kinetics of an activated-sludge reactor system treating poultry slaughterhouse wastewater

The principal objective was to generate the essential kinetic parameters for model simulation and operation management of an activated-sludge reactor (ASR) system treating poultry slaughterhouse wastewater. By varying four different mean cell residence times (θc=4.6–24.3 d), the ASR system (26°C) removed effectively 93.5%–97.2% of chemical oxygen demand (COD) from wastewater. If a high COD removal efficiency and a low effluent volatile suspended solids (VSS) concentration are of great concern, a θc of 15–24 d or a food to microorganism (F/M) ratio of 0.3–0.7 kg COD/kg VSS-d is suggested; if resource sustainability and enhanced operation of the ASR system are of great concern, a θc of 9 d or an F/M ratio of 0.9 kg COD/kg VSS-d is suggested. The COD residual concentrations and COD removal efficiencies calculated by using the Monod model agreed well with the experimental results. When the parameters k and K s (Δ P/P) were respectively varied from−100% to+100%, the parametric sensitivity analysis showed that the COD residual concentration change (Δ S/S) was highly sensitive to k in the Δ P/P range between 0% and−40%, causing a marked increase in COD residual concentration.

Biodigestão anaeróbia de efluente de abatedouro avícola

Objetivou-se, com este trabalho, avaliar o processo de biodigestão anaeróbia no tratamento de efluentes de abatedouro avícola, considerando-se os TRH de 7, 14 e 21 dias, além da adição de enzima lipolítica aos substratos, nas concentrações de 0; 0,5; 1,0 e 1,5 g L-1 de carga adicionada aos biodigestores. A influência dos TRH e da adição de enzima lipolítica aos substratos foi avaliada por meio das produções de biogás e CH4, dos potenciais de produção por DQO, adicionada e removida, bem como pelas reduções dos teores de DQO, concentrações de N, P e K e dos valores de pH. Os resultados obtidos demonstraram que houve influência dos TRH (em que o TRH 7 expressou os melhores resultados, para produção semanal média de biogás, com 40,7 L, e CH4, com 32,2 L) e das concentrações de enzimas, com maiores valores de produção para os tratamentos 1,0 (24,6 L) e 1,5 g L-1 (26,2 L), que não diferiram entre si. As concentrações de enzimas de 1,0 e 1,5 g L-1 apresentaram maiores potenciais de produção de biogás (1,1 e 1,1 L g-1 de DQO adicionada, respectivamente) e metano (0,9 e 0,8 L g¹ de DQO adicionada, respectivamente), quando comparadas com as da 0,5 g L-1 (0,8 e 0,7 L g-1 biogás e CH4, respectivamente) e 0 (0,7 e 0,5 L g-1 biogás e CH4, respectivamente). As maiores remoções de DQO foram alcançadas nas concentrações de 0,5 g L-1 (83,3%) e TRH de 21 dias (74,4%). Contudo, para que haja maior eficiência na reciclagem energética, recomenda-se a utilização de concentrações de 1,0 g L-1 de efluente e tempo de retenção hidráulica de 7 dias.

Treatment of poultry slaughterhouse wastewater in hybrid upflow anaerobic sludge blanket reactor packed with pleated poly vinyl chloride rings

In this study, the performance of 5.4L hybrid upflow anaerobic sludge blanket (HUASB) reactor for treating poultry slaughterhouse wastewater under mesophilic conditions (29–35°C), was investigated. After starting-up, the reactor was loaded up to an OLR of 19kgCOD/m3d and achieved varied TCOD and SCOD removal efficiencies of 70–86% and 80–92%, respectively. The biogas was varied between 1.1 and 5.2m3/m3d with the maximum methane content of 72%. The maximum methane yield was 0.32m3/kgCODremoved at an OLR of 9.27kgCOD/m3d. Black matured granules of size between 2.5 and 5mm were observed at the end of 225d operation. RTD study showed the flow behavior was in mixed regime at the end of performance study. Step wise polynomial regression analysis was fitted well. Methanobacterium and Methanosaeta bacteria were dominant at the end of start-up whereas Methanosarcina, Cocci and rods were predominant at the end of performance studies.

The effect of stirring speed and current density on removal efficiency of poultry slaughterhouse wastewater by electrocoagulation method

The aim of study is to investigate the effect of current density and stirring speed in the treatment of poultry slaughterhouse wastewater (PSW) using electrocoagulation with aluminum electrodes. In the experiments, initial pH and current density were chosen between 3 and 7, and 0.5 and 2.0 mA/cm 2 respectively. The best removal efficiency has been obtained, when initial pH and current density were adjusted to 3.0 and 1.0 mA/cm 2, respectively. Increasing current density values decreased COD removal efficiency. The highest removal efficiencies of 85, 85, 81 and 71% were obtained with the current density of 0.5, 1.0, 1.5 and 2.0 mA/cm 2, respectively. Initial pH values of these removal efficiencies were 4.0, 3.0, 3.0 and 5.0. When experiments were performed to investigate the turbidity removal efficiency, it was found that current density of 1.0 mA/cm 2 provided 98% removal efficiency. Results obtained from the experiments where stirring speed of 100, 150 and 250 rpm were used showed the removal efficiency of 85, 90 and 75% respectively with the current density of 1.0 mA/cm 2. Results showed that electrocoagulation is a suitable method for treatment of PSW. Electrical conductivity of investigated wastewater was nearly 2860 μS/cm, which caused energy consumption to be relatively lower.

Performance of an Anaerobic Reactor Treating Poultry Abattoir Wastewater with High Fat Content After Enzymatic Hydrolysis

Abstract Effects of a lipase-rich solid enzymatic preparation produced by the fungus Penicillium restrictum in solid-state fermentation were evaluated in up-flow anaerobic sludge blanket reactors treating poultry slaughterhouse wastewater with 800 mg oil and grease (O&G)/L. Reactors operated at 30°C under two organic load rates (3.9 and 7.3 kg chemical oxygen demand [COD]/m3·day). The reactor fed with previously hydrolyzed wastewater showed higher methane production values, as well as high COD removal levels (367 and 882 mL CH4/day and 90.4% and 93.5% at 1st and 2nd regimen, respectively). In the reactor fed with raw wastewater, 178 and 642 mL CH4/day and 89.8% and 91.0% of COD removal were verified at 1st and 2nd regimen, respectively. Although differences are not so significant in terms of COD removal and biogas production, the greatest impact on the implementation of solid enzymatic preparation in the prehydrolysis step was the better operating conditions: in the control reactor, frequent episodes of c...