Hydrolysis Tank Research Articles

Microbiome assembly and stability during start-up of a full-scale, two-phase anaerobic digester fed cow manure and mixed organic feedstocks

Carbon transformations during anaerobic digestion are mediated by complex microbiomes, but their assembly is poorly understood, especially in full-scale digesters. Gene-centric metagenomics combining functional and taxonomic classification was performed for an on-farm digester during start-up. Cow manure and organic waste pre-treated in a hydrolysis tank were fed to the methane-producing digester and the volatile solids loading rate was slowly increased from 0 to 3.5 kg volatile solids m−3 d−1 over one year. The microbial community in the anaerobic digester exhibited a high ratio of archaea, which were dominated by hydrogenotrophic methanogens. Bacteria in the anaerobic digester had a high abundance of genes for ferredoxin cycling, H2 generation, and more metabolically complex fermentations than in the hydrolysis tank. In total, the results show that a functionally stable microbiome was achieved quickly during start-up and that the microbiome created in the low-pH hydrolysis tank did not persist in the downstream anaerobic digester.

Effect of oxygen vacancy on electrochemical performance of NiCo-layered double oxides as water splitting electrocatalyst

It is of importance for the design of cost-effective bifunctional electrocatalysts with good durability to decrease the energy rampart of total water decomposition. However, few electrocatalysts simultaneously exhibits excellent catalytic property and durability for both oxygen evolution reaction (OER) as well as hydrogen evolution reaction (HER). Herein, we adopt strategies toward defect engineering coupled with metal organic framework (MOF) to synthesize oxygen vacancy abundant NiCo-layered double oxides with hollow nanotube arrays structures supported on Ni foam (Ov-NiCo-LDO HNTAs/NF) via etching of ZnO template, which is considered as an efficient electrocatalyst for water splitting. The optimal Ov-NiCo-LDO HNTAs/NF reveals an ultra-low overpotential of 149 and 30 mV to afford a current density of 10 mA cm−2 for OER and HER in alkaline solution, respectively. Moreover, the catalyst also displays significant stability for 24 h with no significant decrease when a stable current density of 100 mA cm−2 is applied. A full water splitting system coupled with Ov-NiCo-LDO HNTAs/NF as both poles of hydrolysis tank can drive of 20 mA cm−2 current density at a potential of 1.68 V, along with steady operation for over 24 h, indicating that Ov-NiCo-LDO HNTAs/NF is a promising bifunctional electrocatalyst.

Application Potential of Constructed Wetlands on Different Operation Mode for Biologically Pre-Treatment of Rural Domestic Wastewater

In order to satisfy the requirements of rural domestic sewage, a bio-ecological combination system was proposed, including a biological treatment section (anaerobic hydrolysis tank and aerobic tank) and an ecological post-treatment section. This study observed the application potential of constructed wetlands (CW) on different operation modes for biologically pre-treated rural domestic wastewater. The organics and nutrient removal efficiency of the tidal flow constructed wetland (TFCW) and the horizontal subsurface flow constructed wetland (HFCW) were compared at a temperature range of 20–40 °C. During the stable phase, the higher chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total phosphorus (TP) removal efficiencies existed in TFCW than HFCW, corresponding to the efficiency of COD 69.46%, NH4+-N 96.47%, and TP 57.38%, but lower performance on COD (61.43%), NH4+-N (84.99%), and TP (46.75%) removal in HFCW, which should be attributed to the increasement of aerobic heterotrophic bacteria (Arthrobact and Sphingomonas), nitrifiers (Nitrospira), and phosphate accumulating organisms (PAOs) (Pseudomonas). The microbial biomass was also increased from 2.13 ± 0.14 mg/g (HFCW) to 4.64 ± 0.18 mg/g (TFCW), which proved to strengthen the formation and growth of biofilm under a better oxygen supplement. Based on the relative abundance of functional genera in the microbial community, it showed that TFCW was more favorable for promoting the growth of heterotrophic bacteria, nitrifiers, and phosphate-accumulating organisms (PAOs). When temperature changed from −4 °C to 15 °C, the two-stage constructed wetlands (TFCW-HFCW and HFCW-TFCW) were used for improving the performance of pollutants removal. The results demonstrated that the effluent concentrations of TFCW-HFCW and HFCW-TFCW met the Class 1A discharge standard of DB32/3462-2020 in JiangSu Province, China. Therefore, this study will provide a useful and easy-to-implement technology for the operation as an ecological post-treatment section.

Precipitation and recovery of phosphorus from the wastewater hydrolysis tank

Phosphorus, a limited resource, is also an environmental pollutant that should be removed from wastewater and ideally reused. A pilot-scale facility was set up and used to precipitate and recover phosphorus from wastewater. The return activated sludge in a hydrolysis tank was flocculated and separated and the solid material returned to the hydrolysis tank; the flocculation process did not harm the microorganisms. Phosphate in the reject water was precipitated with different calcium salts and the phosphorus-containing precipitate recovered. The precipitate consisted mainly of phosphate and calcium, and under 5% of the final product consisted of iron and aluminum. Around 20% of the precipitate was organic material. The pilot-scale test was supplemented with bench-scale tests using calcium salt, magnesium salt, and NaOH/KOH. Without the addition of calcium ions, phosphate could be precipitated by increasing pH to 9.5, resulting in a concentration of phosphorus in the reject water of under 2 mg/L. If calcium salt was added (Ca:P ratio of 2:1), it was possible to remove phosphate at pH 9 (<1 mg/L). In general, the concentration of dissolved phosphate was 8–10 mg/L lower after precipitation when calcium salt was used compared with all other tested salts. This difference increased if additional phosphate was added to the sludge. The bench- and pilot-scale experiments yielded comparable data. At the pilot-scale facility, it was possible to remove 90% of the phosphate by adding calcium salt and regulating the pH to 8.5.

SLAUGHTERHOUSE WASTE TO ENERGY IN THE ENERGY TRANSITION WITH PERFORMANCE ANALYSIS AND DESIGN OF SLAUGHTERHOUSE BIODIGESTOR

A performance analysis of an operating slaughterhouse was carried out with the objective of identifying challenges, opportunities and improvement measures through operation and proposal of an optimum design of the biogas plant. The facility slaughters an average of 200 cows and 400 sheep per day producing an average of 16,000 kg of solid waste and 40 m3 of wastewater. The study showed that out of the total solid and liquid waste of about 56,000 kg from the slaughterhouse, only 2,800 kg is utilized in biogas production leaving out 53,200 kg of waste untreated by the biogas digestor. This research proposes the construction of an 80 m3 capacity hydrolysis tank, 1,600 m3capacity digester tank and a 2,000 m3 biogas storage bag for the increased biogas production. Retention time would have to be increased to 20 days from 17 days and substrate PH level increased to 7.0 from average of 6.5. The proposed design will increase biogas production from current 35 m3 to 1,920 m3 and increase solid wasted utilization increase from 1.875% to 75% and that of liquid waste from 6.25% to 100%. Production of biogas and electricity will contribute to greenhouse gas emissions mitigation as one of the wastes to energy pathways in the energy transition. The study concludes that slaughterhouse waste to energy conversion has an important role to play in the sustainable energy transition and a cleaner environment.

Change the original microbial community structure in the hydrolysis acidification tank to enhance the COD removal performance of oily wastewater.

The hydrolysis acidification tank mainly relies on microorganisms to treat oily sewage, but in many cases the chemical oxygen demand (COD) of the effluent from the hydrolysis acidification tank does not decrease or even increase. In this work, about 50 L of oily wastewater is treated in a facultative anaerobic hydrolysis acidification tank with a temperature of 29 °C, pH 6, high-throughput sequencing technology analyzes found that after long-term operation of the hydrolysis and acidification tank, the dominant bacterial Pseudomonas accounted for only 2.87%, at this time, the effluent COD of the hydrolysis and acidification tank was 450 mg/L. Pseudomonas stutzeri LH-42 a strain screened in the laboratory, was domesticated and colonized in the hydrolysis acidification tank. High-throughput sequencing and bioinformatics analysis showed that the proportion of Pseudomonas in the hydrolysis acidification tank reached 5.89%, the effluent COD of the hydrolysis and acidification tank was 200 mg/L. The above results indicate the importance of the proportion of Pseudomonas in the hydrolysis and acidification tank for the COD degradation of oily wastewater.

Ultradispersed Ir x Ni clusters as bifunctional electrocatalysts for high-efficiency water splitting in acid electrolytes.

Design and synthesis of electrocatalysts with high activity and low cost is an important challenge for water splitting. We report a rapid and facile synthetic route to obtain IrxNi clusters via polyol reduction. The IrxNi clusters show excellent activity for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic electrolytes. The optimized Ir2Ni/C clusters exhibit an electrochemical active area of 18.27 mF cm−2, with the overpotential of OER being 292 mV and HER being 30 mV at 10 mA cm−2, respectively. In addition, the Ir2Ni/C used as the cathode and anode for the H-type hydrolysis tank only needs 1.597 V cell voltages. The excellent electrocatalytic performance is mainly attributed to the synergistic effect between the metals and the ultra-fine particle size. This study provides a novel strategy that has a broad application for water splitting.

Enhancing biodegradability of industrial park wastewater by packing carriers and limited aeration in the hydrolysis process

This study aims to ameliorate effects of packing carriers, filling ratio, temperature and limited aeration on hydrolysis performance in a chemical industrial park wastewater treatment plant. Illumina-MiSeq sequencing was applied to compare microbial community structure between biofilm attached on carriers and activated sludge in a full-scale hydrolysis tank. Packing carriers intensified the plentifulness of microbial community, enriched hydrolytic bacteria (Betaproteobacteria, Gammaproteobacteria, Sphingobacteria, Clostridia, Bacteroidia), and enhanced biodegradability of organics in the wastewater. Rising carriers filling ratio increased first-order kinetic constant of hydrolysis from 0.015 to 0.080 h−1, and decreased fractions inert to hydrolysis. Rising temperature stimulated enzymatic activity for hydrolysis with activation energy of 80.22 kJ/mol. Limited aeration further enriched hydrolytic bacteria, inhibited sulfate-reducing bacteria and intensified biodegradability of organic substances. Variations of fluorescent organic substances and ammonia nitrogen release during hydrolysis confirmed that hydrolysis was strengthened by packing carriers, increasing filling ratio, enhancing temperature and introducing limited aeration. Packing carriers and limited aeration were techno-economic methods for enhancing hydrolysis performance in the chemical industrial park wastewater treatment plant by enriching hydrolytic bacteria and stimulating their activities.

A novel metabolic-ASM model for full-scale biological nutrient removal systems

This study demonstrates that META-ASM, a new integrated metabolic activated sludge model, provides an overall platform to describe the activity of the key organisms and processes relevant to biological nutrient removal (BNR) systems with a robust single-set of default parameters. This model overcomes various shortcomings of existing enhanced biological phosphorous removal (EBPR) models studied over the last twenty years. The model has been tested against 34 data sets from enriched lab polyphosphate accumulating organism (PAO)-glycogen accumulating organism (GAO) cultures and experiments with full-scale sludge from five water resource recovery facilities (WRRFs) with two different process configurations: three stage Phoredox (A2/O) and adapted Biodenitro™ combined with a return sludge sidestream hydrolysis tank (RSS). Special attention is given to the operational conditions affecting the competition between PAOs and GAOs, capability of PAOs and GAOs to denitrify, metabolic shifts as a function of storage polymer concentrations, as well as the role of these polymers in endogenous processes and fermentation. The overall good correlations obtained between the predicted versus measured EBPR profiles from different data sets support that this new model, which is based on in-depth understanding of EBPR, reduces calibration efforts. On the other hand, the performance comparison between META-ASM and literature models demonstrates that existing literature models require extensive parameter changes and have limited predictive power, especially in the prediction of long-term EBPR performance. The development of such a model able to describe in detail the microbial and chemical transformations of BNR systems with minimal adjustment to parameters suggests that the META-ASM model is a powerful tool to predict and mitigate EBPR upsets, optimise EBPR performance and to evaluate new process designs.

Optimization of Scheduling in Ethanol Production from Oil Palm Empty Fruit Bunch Process

In this research, the scheduling Batch process had done for minimizing the processing time and the highest equipment efficiency of the ethanol production process. Aspen Plus program was used to perform the mass and balances in the steady state part, and Aspen Batch Process Developer program was used to schedule batch parts of the process. The production process from oil palm empty fruit bunch has the ethanol capacity of 9,200 kg per day. The raw materials are oil palm empty fruit bunch 47,000 kg per day. There are four production schedules: one hydrolysis tank and one fermentation tank, four hydrolysis tanks and a fermentation tank, one hydrolysis tank and four fermentation tanks, four tanks of hydrolysis and four tanks of fermentation. This can reduce time consumption in one production cycle and less cycle time

Isolation, identification and characterization of lignocellulolytic aerobic and anaerobic fungi in one- and two-phase biogas plants

Aerobic and anaerobic fungi are among the most effective plant biomass degraders known and have high potential to increase the efficiency of lignocellulosic biomass utilization, such as for biogas generation. However, limited information is available on their contribution to such industrial processes. Therefore, the presence of fungi along the biogas production chain of one-phase and two-phase biogas plants in Germany was analyzed. Seventeen aerobic species of Zygomycota, Ascomycota and Basidiomycota were identified, including efficient producers of lignocellulases, such as Trichoderma capillare isolated from a hydrolysis tank and Coprinopsis cinerea from fibers separated from pressed digestate. Five anaerobic fungal species of the phylum Neocallimastigomycota (comprising two novel clades) were present in an slightly acidic fermenter of a biogas plant fed with cow manure displaying endoglucanase transcriptional activity. The broad fungal presence demonstrated in this study can serve developing bioaugmentation systems with relevant lignocellulolytic fungi to improve biogas production from recalcitrant fiber material.

Effect of thermal pretreatment at 70 °C for one hour (EU hygienization conditions) of various organic wastes on methane production under mesophilic anaerobic digestion

The impact of hygienization as mild thermal pretreatment on the methane production of various organic wastes was investigated, including digestate issued from hydrolysis tank, thickened sludge from a municipal wastewater treatment plant (MWWTP sludge) and from a mixed domestic-industrial wastewater treatment plant (D-I WWTP sludge), sludge from a meat-processing plant (MP sludge), sieving rejection from a pork slaughterhouse, pork liver, cattle slurry, cattle scraping slurry and date seeds. They were thermally pretreated at 70 °C for one hour and subsequently put into AD digesters incubated at 37 °C for individual methane potential test. The modified Gompertz model was employed to evaluate the kinetic parameters of methane production curves (R2 = 0.944–0.999). The results were compared with the untreated samples. Significant enhancement of methane potentials induced by thermal treatment (p < 0.05) was observed when it comes to the pork liver (+8.6%), the slaughterhouse sieving rejection (+11.1%), the thickened MWWTP sludge (+12.5%) and the digestate issued from hydrolysis tank (+18.0%). The maximum methane production rates of the 4 substrates mentioned above were increased by thermal pretreatment as well (from 13.5% to 64%, p < 0.05). The lag time of the methane production was shortened for the digestate from hydrolysis tank and the MWWTP sludge (by 48.6% and 62.2% respectively, p < 0.05). No significant enhancement was obtained for the cattle slurry, the cattle scraping slurry and the D-I WWTP sludge. Additionally, the maximum methane production rate and the methane potential were reduced by thermal pretreatment for the MP sludge and the date seeds respectively (p < 0.05). In this paper, possible mechanisms were discussed to explain the different methane production behaviors of substrates after the mild thermal pretreatment.

Maize cob waste pre-treatments to enhance biogas production through co-anaerobic digestion with OFMSW

In the present work, the enhancement of biogas and methane yields through anaerobic co-digestion of the pre-hydrolised Organic Fraction of Municipal Solid Wastes (hOFMSW) and Maize Cob Wastes (MCW) in a lab-scale thermophilic anaerobic reactor was tested. In order to increase its biodegradability, MCW were submitted to an initial pre-treatment screening phase as follows: (i) microwave (MW) irradiation catalysed by NaOH, (ii) MW catalysed by glycerol in water and alkaline water solutions, (iii) MW catalysed by H2O2 with pH of 9.8 and (iv) chemical pre-treatment at room temperature catalysed by H2O2 with 4 h reaction time. The pre-treatments cataysed by H2O2 were performed with 2% MCW (wMCW/v alkaline water) at ratios of 0.125, 0.25, 0.5 and 1.0 (wH2O2/wMCW). The pre-treatment that presented the most favourable balance between sugars, lignin, cellulose and hemicellulose solubilisations, as well as low production of phenolic compound and furfural (inhibitors), was the chemical pre-treatment catalysed by H2O2, at room temperature, with a ratio of 0.5 wH2O2/wMCW (Pre1). This Pre1 was then optimised testing reaction times of 1, 2 and 3 days at a different pH (11.5) and MCW percentage (10% w/v). The optimised pre-treatment that presented the best results, considering the same criteria defined above, was the one carried out during 3 days, at pH 9.8 and 10% MCW w/v (Pre2).The anaerobic reactor was initially fed with the hOFMSW obtained from the hydrolysis tank of an industrial AD plant. The hOFMSW was than co-digested with MCW submitted to the pre-treatment Pre1. In another assay, hOFMSW was co-digested with MCW submitted pre-treatment Pre 2. The co-digestion of hOFMSW + Pre1 increased the biogas yield by 38.9% and methane yield by 29.7%, when compared to the results obtained with hOFMSW alone. The co-digestion of hOFMSW + Pre2 increased biogas yield by 46.0% and CH4 yield by 36.3%. In both cases, the methane content obtained in the biogas streams was above 66% v/v. These results show that pre-treatment with H2O2, at room temperature, is a promising low cost way to valorize MCW through co-digestion with hOFMSW.

PEMBUATAN BIOETANOL DARI TEPUNG AMPAS TEBU MELALUI PROSES HIDROLISIS TERMAL DAN FERMENTASI SERTA RECYCLE VINASSE (PENGARUH KONSENTRASI TEPUNG AMPAS TEBU, SUHU DAN WAKTU HIDROLISIS)

The purpose of this research are to study the effect of sugarcane bagasse powder concentration, hydrolysis temperature and time on the yield of glucose and the level of glucose by recycle vinasse process. Raw sugarcane bagasse as primary material was obtained from sugarcane juice shop. Observed variabels were concentration of sugarcane bagasse, hydrolysis time and temperature. Sugarcane bagasse is powdered by blender and then mixed with aquadest (2,94; 3,85; 4,76%) and hydrolized in the hydrolysis tank. The hydrolysis process occured at 1, 1,5 and 2 hours and temperature 135, 150 and 165°C. The hydrolysis products were tested for its glucose, lignin and cellulose composition. After that, the product was fermented in order to produce bioethanol. The fermented product was filtered for its vinasse and it will be used as the feed of hydrolysis recycle process. Result showed that yield of glucose increases as the increase of sugarcane bagasse powder concentration, hydrolysis time and temperature. But, yield of glucose increases from 1 until 1,5 hour of hydrolysis time and then decreases from 1,5 to 2 hour of hydrolysis time. The highest yield of glucose (31,022%) was obtained at concentration 2,94%, 165 °C and 2 hours of hydrolysis time. Lignin and cellulose level fluctuated as the increasing of hydrolysis temperature. This might be caused by the non-uniform composition by the raw materials.

Effect of mixing on enzymatic hydrolysis of cardboard waste: Saccharification yield and subsequent separation of the solid residue using a pressure filter

Cellulosic wastes, from sources such as low-quality cardboard and paper, are regarded as potential feedstocks for bioethanol production. One pathway from these cellulosic materials to ethanol is saccharification (hydrolysis) followed by fermentation. Saccharification is commonly performed using enzymes that are able to cleave the cellulosic structure to smaller units, preferably to glucose monomers. During the hydrolysis, mixing conditions have a considerable impact on the performance of the enzymes. Thus mixing conditions in the hydrolysis tank can also influence the downstream operations and, consequently, the overall economy of the bioethanol process. In this experimental study, four types of impeller, at different hydrolysis conditions were used. The effect of mixing on the glucose yield and on the filtration characteristics of the hydrolysate was evaluated. It was shown that not only the sugar yield depended on the mixing conditions: the effect on the solid–liquid separation step was even more significant.

A simplified kinetic model for a full scale anaerobic wastewater treatment plant of a sugar factory under unsteady conditions

Abstract A simplified time dependent mathematical model was developed for an industrial a full-scale two stage anaerobic wastewater treatment plant of a sugar factory under unsteady conditions. As an overall approach, a two-step (acidogenesis and methanogenesis) instantaneous mass balance was considered in the model. The reactor equations employed were based on continuous flow well-mixed conditions. Kinetic parameters related to acidogenic and methanogenic reactions were imported from literature studies. The kinetic model was used to simulate MLVSS (mixed liquor volatile suspended solids), VFA (volatile fatty acid) and COD (chemical oxygen demand) equivalent glucose concentrations in hydrolysis tank, and MLVSS, VFA and gas production in anaerobic tank by making use of data from the full-scale anaerobic methane production plant. The model satisfactorily predicted the measured variables in the hydrolysis tank, but prediction was poor for variables in the anaerobic tank. The model has limitations in anaerobi...

Modeling and Simulation of Dissolved Oxygen Concentrations in a Full-Scale Textile Dyeing Wastewater Treatment Plant

A Modified Activated Sludge Model No.1 (M-ASM1), including six COD components (SI, SS, XI, XS, XH and SO) and three biochemical processes (aerobic growth of heterotrophs, aerobic decay of heterotrophs and hydrolysis of entrapped organics) is used to simulate the anaerobic hydrolysis-aeration- sedimentation treatment series in a full-scale textile dyeing wastewater treatment plant with an influent flowrate of 200,000 m3/d. M-ASM1 has the following characteristics: (1) the effect of temperature variation on biochemical reactions is included; (2) adding a parameter: ?. Using this parameter, the anaerobic hydrolysis tank and the aerobic initial compartments in which the dissolved oxygen concentrations are equal to "0 mg/L" can be differentiated; (3) the oxygen transfer coefficient KLa is excluded. Namely, as long as inputting the aeration flowrate, the pressure in the aeration pipe and other running data on air supply into this model, M-ASM1 can simulate the oxygen concentrations of each compartment in a plug-flow aeration tank.

Hydrolysis and fermentation of activated sludge to enhance biological phosphorus removal

The conventional mainstream enhanced biological phosphorus removal (EBPR) process depends on the quality of the raw incoming wastewater. An alternative sidestream EBPR process is presented, where the substrates for storage by the polyphosphate accumulating organisms (PAOs) instead come from hydrolysis of the return activated sludge. This process is studied in full-scale at two treatment plants and quantified by means of phosphorus release rates and readily biodegradable COD (RBCOD) accumulation rates. It was seen that not only was a significant amount of RBCOD stored by PAOs but an approximately equal amount was accumulated in the sidestream hydrolysis tank and made available for the subsequent nitrogen removal process. The phosphorus release of the sludge with and without addition of different substrates was furthermore studied in laboratory scale. The study showed that the process is promising and in a number of cases will have significant advantages compared with the conventional mainstream EBPR

Pilot-scale conversion of manure—straw mixtures to methane

A pilot-scale two-stage fermentation system designed to accomodate manure—straw mixtures was evaluated. The mixture was composed of 50% beef cattle manure and 50% wheat straw based on volatile solids (VS) content. The manure—straw mixture was mixed into a slurry and fermented in a hydrolysis tank for 1 day. The slurry in the hydrolysis tank was observed to autoheat from 40°C up to about 60°C, due to aerobic hydrolysis of substrate and mixing energy dissipation. Slurry from the hydrolysis tank either passed through a vibrating-screen solids separator or went directly to the anaerobic fermentor. When the solids were separated, approximately 37% of the screened solids were returned to the hydrolysis tank. The screened liquid, which accounted for 35% of the VS in the manure and straw, was pumped to the anaerobic fermentor for conversion to methane (CH 4). The fermentor, operated at 8-day hydraulic retention time (HRT), 44 to 47°C, and influent concentration of 47.3 kg VS/m 3, produced 1.81 m 3 CH 4/m 3 fermentor·day and 0.31 m 3 CH 4/kg VS fed. When solids were not removed, the fermentor was operated at 5-day HRT, 52 to 54°C and influent concentration of 68.1 kg VS/m 3. The CH 4 production rate and yield were 2.96 m 3 CH 4/m 3 fermentor·day, and 0.22 m 3 CH 4/kg VS fed, respectively. After correcting for differences in fermentation temperature and HRT, the system with solids separation produced only 58% of the daily CH 4 production of the system without solid separation.