Anaerobic filter treatment of fishery wastewater

Anaerobic treatment of wastewater from a selected seafood processing plant was conducted at organic loading rates (OLR) ranging from 0.3 to 1.8 kg chemical oxygen demand (COD)/m³.day and hydraulic retention times (HRT) ranging from 36 to 6 days. COD reduction decreased with increasing OLR. More than 75% COD reduction could be maintained up to an OLR of about 1 kg COD/m³.day with an HRT of 11 days. An OLR of 1.3 kg COD/m³.day corresponding to an HRT of 6.6 days gave maximal biogas productivity of 1.5 m³/m³.day or 1.3 m³ biogas/kg COD with a 65% COD reduction. If the HRT was kept constant at 11 days, an OLR of 1.3 kg COD/m³.day achieved maximal biogas productivity (1.1 m³/m³.day) and yield (0.75 m³/kg COD) and a 60% COD reduction for treatment of tuna condensate.P. Prasertsan and S. Jung are with the Department of Agro-Industry, Faculty of Natural Resources, Prince of Songkla University, Hatyai 90110, Thailand. K.A. Buckle is with the Department of Food Science and Technology, University of New South Wales, Kensington, NSW 2033, Australia.     

Thermophilic anaerobic digestion of Lurgi coal gasification wastewater in a UASB reactor

Lurgi coal gasification wastewater (LCGW) is a refractory wastewater, whose anaerobic treatment has been a severe problem due to its toxicity and poor biodegradability. Using a mesophilic (35 ± 2 °C) reactor as a control, thermophilic anaerobic digestion (55 ± 2 °C) of LCGW was investigated in a UASB reactor. After 120 days of operation, the removal of COD and total phenols by the thermophilic reactor could reach 50-55% and 50-60% respectively, at an organic loading rate of 2.5 kg COD/(m³ d) and HRT of 24 h; the corresponding efficiencies were both only 20-30% in the mesophilic reactor. After thermophilic digestion, the wastewater concentrations of the aerobic effluent COD could reach below 200 mg/L compared with around 294 mg/L if mesophilic digestion was done and around 375 mg/L if sole aerobic pretreatment was done. The results suggested that thermophilic anaerobic digestion improved significantly both anaerobic and aerobic biodegradation of LCGW.     

Anaerobic treatment of winery wastewater using laboratory-scale multi- and single-fed filters at ambient temperatures

A lab-scale investigation was conducted to examine the effectiveness of a multi-fed upflow anaerobic filter process for the methane production from a rice winery effluent at ambient temperatures. The experiment was carried in two identical 3.0-l upflow filters, a single-fed reactor and a multi-fed reactor. The results showed that the multi-fed reactor, operated at the ambient temperatures of 19–27 °C and influent chemical oxygen demand (COD) of 8.34–25.76 g/l, could remove over 82% of COD even at an organic loading rate (OLR) of 37.68 g-COD/l d and a short hydraulic retention time (HRT) of 8 h. This reactor produced biogas with a methane yield of 0.30–0.35 l-CH₄/g-COD_removed. The multi-fed upflow anaerobic filter was proved to be more efficient than the single-fed reactor in terms of COD removal efficiency and stability against hydraulic loading shocks. A linear-regression model with influent COD concentration and HRT terms adequately described the multi-fed upflow anaerobic filter system for the treatment of rice winery wastewater at ambient temperatures.     

Anaerobic fixed film wastewater treatment

The anaerobic methane fermentation process has long been used in the field of wastewater engineering in sludge processing, mainly for waste stabilization and solids reduction. Recently, major advances in the fundamental understanding of the process microbiology and biochemistry, along with the development of new reactor configurations have promoted a resurgence of interest in the use of this technology for the processing of liquid industrial and municipal wastewaters. Three of these new processes, the anaerobic filter, expanded/fluidized bed, and upflow anaerobic sludge blanket, are discussed.Each of these processes is a fixed film process, which enables the attainment of high solids retention times for good system efficiency and stability, with low hydraulic retention times for system economy. Fixed film anaerobic processes are able to realize many of the benefits of anaerobic processes while overcoming many of the problems historically associated with anaerobic processes.Each of the processes is described, and examples are presented for industrial and municipal applications. Finally, the processes are qualitatively compared. At present, it is not possible to say which reactor configuration is best. In fact, the selection is often dependent on wastewater characteristics, local factors, and several other factors. More full-scale data and operating experience along with basic research needs are needed to clarify further this situation, and to design these systems optimally.     

Post-Treatment Options for the Anaerobic Treatment of Domestic Wastewater

This paper focuses on the post-treatment options for the anaerobic treatment of domestic wastewater. Initially, the main limitations of anaerobic systems regarding carbon, nutrients and pathogen removal are presented. In sequence, the advantages of combined anaerobic/aerobic treatment and the main post-treatment options currently in use are discussed, including the presentation of flowsheets and a comparison between various post-treatment systems. Lastly, the paper presents a review of emerging options and possible improvements of current post-treatment alternatives.     

High rate anaerobic digestion of a petrochemical wastewater using biomass support particles

Anaerobic digestion of wastewater from a dimethyl terephthalate plant was studied in continuously stirred tank reactors with plastic net biomass support particles (BSP) at a level of 20% (v/v). The experimental results showed that the BSP system could treat the wastewater at a hydraulic retention time as low as 1.5 d, organic loading as high as 20 kg COD/m3/d and at acidic feed pH as low as 4.5 with 95% COD reduction and biogas production of about 8l/l/d, while the control system without support particles could not treat the wastewater above a 5-d hydraulic retention time, 5 kg COD/m3/d organic loading and a feed pH of 6.0. Thus, augmentation of BSP upgraded the performance of the conventional suspended growth system to an equivalent level to advanced reactors.     

Stability and reproducibility of low-temperature anaerobic biological wastewater treatment

The reproducibility of low-temperature anaerobic biological wastewater treatment trials was evaluated. Two identical anaerobic expanded granular sludge bed bioreactors were used to treat synthetic volatile fatty acid-based industrial wastewater under ambient conditions (18-20 degrees C) and to investigate the effect of various environmental perturbations on reactor performance and microbial community dynamics, which were assessed by chemical oxygen demand removal or effluent volatile fatty acid determination and terminal restriction fragment length polymorphism analysis, respectively. Methanogenic activity was monitored using specific methanogenic activity assays. Reactor performance and microbial community dynamics were each well replicated between Reactor 1 and Reactor 2. Archaeal dynamics, in particular, were associated with reactor operating parameters. Terminal restriction fragment length polymorphism data suggested dynamic acetoclastic and hydrogenophilic methanogenic populations and were in agreement with temporal specific methanogenic activity data. Putative psychrophilic populations were observed in anaerobic bioreactor sludge for the first time.     

Anaerobic treatment of 2,4,6-trichlorophenol in an expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactor at 15 degrees C

Expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors were operated at 15 degrees C for the treatment of 2,4,6-trichlorophenol (TCP)-containing volatile fatty acid (VFA)-based wastewaters. The seed sludge used as inoculum for the control (no TCP) and test reactor was unexposed to chlorophenols (CPs) prior to the 425-day trial. TCP supplementation to the feed at 50 mg TCPl(-1) partially inhibited the anaerobic degradation of the VFA feed measured as COD removal efficiency. However, the withdrawal and subsequent application of stepwise increments to the TCP loading resulted in steady COD removal. Terminal restriction fragment length polymorphism analysis showed Methanosaeta-like Archaea in the control reactor over the experimental period. Different methanogenic populations were detected in the test reactor and responded to the changes in feed composition. Bacterial community analyses indicated changes in the community structure over time and suggested the presence of Campylobacter-like, Acidimicrobium-like and Heliophilum-like organisms in the samples. TCP mineralisation was by a reductive dechlorination pathway through 2,4-dichlorophenol (DCP) and 4-chlorophenol (4-CP) or 2-chlorophenol (2-CP). CP degradation rates in sludge granules from the lower chamber of the hybrid EGSB-AF reactor was in the order TCP > DCP > 4-CP > 2-CP. However, a biodegradability order of lower CPs > TCP was observed in fixed-film biomass taken from the upper reactor chamber, thus reflecting the role of this reactor section in the metabolism of residual lower CPs from the lower sludge-bed stage of operation.     

Critical review of the influences of nanoparticles on biological wastewater treatment and sludge digestion

Nanoparticles (NPs), with at least one dimension less than 100?nm, are substantially employed in consumer and industrial products due to their specific physical and chemical properties. The wide uses of engineered NPs inevitably cause their release into the environment, especially wastewater treatment plants. Therefore, it is essential to systematically assess their potential impact on biological wastewater treatment and subsequent sewage sludge digestion. This review aims to provide such support. First, this paper reviews the recent advances on the analytical developments and nano–bio interface of NPs in wastewater and sewage sludge treatment. The effects of NPs on biological wastewater treatment and sewage sludge digestion and related mechanisms are discussed in detail. Finally, the key questions that need to be answered in the future are pointed out, which include on-line revelation of the changes of NPs in sewage and sludge environments, in situ assessment of the variations of microorganisms involved in these biological systems after they are exposed to NPs. Differentiation of the contribution of individual toxicity mechanisms to these systems, and the identification of under what conditions the nanoparticle-induced toxicity will be increased or decreased are also considered.     

Full-scale and laboratory-scale anaerobic treatment of citric acid production wastewater

This paper reviews the operation of a full-scale, fixed-bed digester treating a citric acid production wastewater with a COD: sulphate ratio of 3–4 : 1. Support matrix pieces were removed from the digester at intervals during the first 5 years of operation in order to quantify the vertical distribution of biomass within the digester. Detailed analysis of the digester biomass after 5 years of operation indicated that H2 and propionate-utilising SRB had outcompeted hydrogenophilic methanogens and propionate syntrophs. Acetoclastic methanogens were shown to play the dominant role in acetate conversion. Butyrate and ethanol-degrading syntrophs also remained active in the digester after 5 years of operation.Laboratory-scale hybrid reactor treatment at 55 °C of a diluted molasses influent, with and without sulphate supplementation, showed that the reactors could be operated with high stability at volumetric loading rates of 24 kgCOD.m-3.d-1 (12 h HRT). In the presence of sulphate (2 g/l-1; COD/sulphate ratio of 6 : 1), acetate conversion was severely inhibited, resulting in effluent acetate concentrations of up to 4000 mg.l-1.     

生物化学中厌氧消化代谢途径的教学实践

厌氧消化是乳酸和乙醇发酵之外的另一条重要的无氧分解代谢途径,对促进资源高效利用、维持生态平衡、优化能源结构、缓解能源危机、推动实施“双碳”战略都具有重要意义。如此重要的代谢过程在大学生物化学课程教材和教学中没有涉及,使得教学体系不完整,亟需教学改革。厌氧消化过程涉及的反应众多,代谢途径复杂,为了让学生全面了解这一过程,教师通过查阅大量文献,将厌氧消化的主要反应途径归纳成图,较为完整地展现厌氧消化代谢过程,并通过BOPPPS教学模式融入课堂教学中。以代谢途径全图的形式直观展示分散冗杂的代谢过程,可以帮助学生构建厌氧消化代谢的系统框架,有助其丰富代谢知识体系,达到了良好的教学效果。本文介绍了厌氧消化代谢途径的内容及教学过程的设计,为生物化学、环境工程微生物学、新能源工程等课程教材的修订及相关课堂教学改革提供参考和借鉴。     

Feasibility assay in phase-separated anaerobic treatment of cheese industry wastewater

This research was conducted as a part of continuous development of innovative bioprocess technology for the treatment of high strength wastewater. Mixed cheese processing wastewater was tested for the feasibility of phase separated anaerobic digestion in batch mode. Three concentrations of soluble chemical oxygen demand (SCOD) made by dilution of raw wastewater were tested for acidification of organics in the wastewater at two pHs, 6.0 and neutral. More than 95% of fat, 97% of soluble protein and 100% of lactose in the mixed waste were acidified in the acidogenic phase. Three different concentrations of artificial substrate consisting of a mixture of short chain organic acids, acetic, propionic, butyric, and valeric acids, along with alcohol were investigated for waste stabilization in methanogenic phase experiments. More than 95% of SCOD reduction was achieved in the methanogenic phase. This translated that 73.5–83.8% of organics in the wastewater could be recovered as energy (methane gas) instead of massive production of sludge.     

Anaerobic treatment of sulphate-containing waste streams

Sulphate-containing wastewaters from the paper and board industry, molasses-based fermentation industries and edible oil refineries present difficulties during anaerobic treatment, leading to problems of toxicity, reduction in methane yield, odour and corrosion. The microbiology and biochemistry of dissimilatory sulphate reduction are reviewed in order to illustrate the potential competition between sulphate reducers and other anaerobes involved in the sequential anaerobic mineralisation process. The theoretical considerations which influence the outcome of competition between sulphate reducers and fermentative, syntrophic, homoacetogenic and methanogenic bacteria are discussed. The actual outcome, under the varying influent organic composition and strength and sulfate concentrations which prevail during digestion of industrial wastewaters, may be quite different to that predicted by thermodynamic or kinetic considerations. The factors governing competitive interactions between SRB and other anaerobes involved in methanogenesis is discussed in the context of literature data on sulphate wastewater treatment and with particular reference to laboratory and full-scale digestion of citric acid production wastewater.     

Protein degradation during anaerobic wastewater treatment: derivation of stoichiometry

The stoichiometry of reactions that describe protein degradation in anaerobic treatment systems were investigated. A methodology was developed to describe protein degradation to organic acids using a single reaction step. The reactions for individual amino acid fermentation and their mediating organisms were reviewed. The dominant fermentation pathways were selected based on a number of assumptions. Using the amino acid content of a model protein, it was then possible to determine stoichiometric coefficients for each major organic acid product in the overall degradation of the protein. The theoretical coefficients were then compared to those determined from two experimental runs on a continuously-fed, well-mixed, laboratory-scale anaerobic wastewater treatment system. In general, the coefficients compared well thus validating the use of a single reaction step for the overall catabolic reaction of protein degradation to organic acids. Furthermore, even when the protein concentration in feed or the feed flow rate was doubled, the amino acid fermentation pathways were found to occur predominantly by only one pathway. Although the choice of Stickland reactions over uncoupled degradation provided good comparisons, an electron balance showed that only about 40% of the amino acids could have proceeded coupled to other amino acid reactions. Uncoupled degradation of the remaining amino acids must have relied on the uptake of hydrogen produced from these reactions by hydrogen-consuming methane bacteria.     

Perturbation‐independent community development in low‐temperature anaerobic biological wastewater treatment bioreactors

The reproducibility and stability of low‐ temperature anaerobic wastewater treatment systems undergoing transient perturbations was investigated. Three identical anaerobic expanded granular sludge bed‐based bioreactors were used to degrade a volatile fatty acid and glucose‐based wastewater under sub‐ambient (15°C) conditions. The effect of a variety of environmental perturbations on bioreactor performance was assessed by chemical oxygen demand removal. Temporal microbial community development was monitored by denaturation gradient gel electrophoresis (DGGE) of 16S rRNA genes extracted from sludge granules. Methanogenic activity was monitored using specific methanogenic activity assays. Bioreactor performance and microbial population dynamics were each well replicated between both experimental bioreactors and the control bioreactor prior to, and after the implementation of most of the applied perturbations. Gene fingerprinting data indicated that Methanosaeta sp. were the persistent, keystone members of the archaeal community, and likely were pivotal for the physical stability and maintenance of the granular biofilms. Cluster analyses of DGGE data suggested that temporal shifts in microbial community structure were predominantly independent of the applied perturbations. Biotechnol. Bioeng. 2010;105: 79–87. © 2009 Wiley Periodicals, Inc.     

Software Sensors to Monitor the Dynamics of Microbial Communities: Application to Anaerobic Digestion

A mass balance based model has been derived to represent the dynamical behavior of the ecosystem contained in an anaerobic digester. The model considers two bacterial populations: acidogenic and methanogenic bacteria. It forms the basis for the design of a software sensor considering both a model of the biological system and on-line gaseous measurements. The software sensor computes the concentration of inorganic carbon and volatile fatty acids (VFA) in the digester. Another software sensor is dedicated to the estimation of the bacterial biomasses. The predictions of the software sensors for a real experiment are very close to the actual off-line measurements. The software sensors monitor the accumulation of VFA and thus very early detect a destabilization of the digester due to overloading. The presented methodology demonstrates the usefulness of advanced monitoring techniques for an improved understanding of the internal working of a biological system.     

Color removal of real textile wastewater by sequential anaerobic and aerobic reactors

Textile wastewater from the Pusan Dyeing Industrial Complex (PDIC) was treated utilizing a two-stage continuous system, composed of an upflow anaerobic sludge blanket reactor and an activated sludge reactor. The effects of color and organic loading rates were studied by varying the hydraulic retention time and influent glucose concentration. The maximum color load to satisfy the legal discharge limit of color intensity in Korea (400 ADMI, unit of the American Dye Manufacturers Institute) was estimated to be 2,700 ADMI·L⁻¹ day⁻¹. This study indicates that the two-stage anaerobic/aerobic reaction system is potentially useful in the treatment of textile wastewater.     

Anaerobic digestion of secondary residuals from an anaerobic bioreactor at a brewery to enhance bioenergy generation

Many beer breweries use high-rate anaerobic digestion (AD) systems to treat their soluble high-strength wastewater. Biogas from these AD systems is used to offset nonrenewable energy utilization in the brewery. With increasing nonrenewable energy costs, interest has mounted to also digest secondary residuals from the high-rate digester effluent, which consists of yeast cells, bacteria, methanogens, and small (hemi)cellulosic particles. Mesophilic (37 °C) and thermophilic (55 °C) lab-scale, low-rate continuously-stirred anaerobic digestion (CSAD) bioreactors were operated for 258 days by feeding secondary residuals at a volatile solids (VS) concentration of ∼40 g l⁻¹. At a hydraulic retention time (HRT) of 15 days and a VS loading rate of 2.7 g VS l⁻¹ day⁻¹, the mesophilic bioreactor showed an average specific volumetric biogas production rate of 0.88 l CH₄ l⁻¹ day⁻¹ and an effluent VS concentration of 22.2 g VS l⁻¹ (43.0% VS removal efficiency) while the thermophilic bioreactor displayed similar performances. The overall methane yield for both systems was 0.21 l CH₄ g⁻¹ VS fed and 0.47–0.48 l CH₄ g⁻¹ VS removed. A primary limitation of thermophilic digestion of this protein-rich waste is the inhibition of methanogens due to higher nondissociated (free) ammonia (NH₃) concentrations under similar total ammonium (NH₄ ⁺) concentrations at equilibrium. Since thermophilic AD did not result in advantageous methane production rates or yields, mesophilic AD was, therefore, superior in treating secondary residuals from high-rate AD effluent. An additional digester to convert secondary residuals to methane may increase the total biogas generation at the brewery by 8% compared to just conventional high-rate digestion of brewery wastewater alone. JIMB-2008: BioEnergy—Special issue.     

Comprehensive modeling of methanogenic biofilms in fluidized bed systems: Mass transfer limitations and multisubstrate aspects

A cognitive model for anaerobic digestion in fluidized bed reactors is developed. The general pathway of the process is divided into five main reactions performed by different bacterial groups. Molecular diffusion of each substrate involved in the reaction scheme is described. Effectiveness factor calculations are performed in steady state for each bacterial group taken into account in the process. The case of a single substrate removal is discussed, and optimal biofilm sizes are found. Sequential substrate removal is investigated, and different kinetic regimes are characterized. The influence of biofilm size and primary substrate removal is discussed in the case of standard concentrations in the liquid phase. This study shows that, according to the theoretical model the limiting step of the process may be different and depends in a large way on mass transfer effects. Finally, importance of biofilm size is compared for acidogenic and methano-genic steps: each reaction is found to be optimized for different biofilm thicknesses. This result may be of interest for design purposes and further dynamic modeling. Concluding remarks concerning the validation of the model are made, and a comparison to experimental data from the literature is presented. (c) 1995 John Wiley & Sons, Inc.     

Anaerobic granulation technology for wastewater treatment

Anaerobic wastewater treatment using granular sludge reactors is a developing technology, in which granular sludge is the core component. So far, around 900 anaerobic granular sludge units have been operated worldwide. Although intensive research attention has been given to anaerobic granules in the past 20 years, the mechanisms responsible for anaerobic granulation and the strategy of how to expedite substantially the formation of granular sludge have not yet been completely clear. This paper reviews the mode of anaerobic granulation, including the mechanisms and models for anaerobic granulation, major factors influencing anaerobic granulation, characteristics of anaerobic granules, anaerobic granulation in other types of reactors, industrial application of anaerobic granulation technology and neural fuzzy model-based control strategy developed for anaerobic systems. Some approaches for future research are outlined.