Laboratory-scale Activated Sludge System Research Articles

Study on the compatibility of a treated effluent from automobile industry with conventional municipal activated sludge process

AbstractThe on-site-treated effluent from an automobile manufacturing company is discharged into the public sewage system for further treatment. However, the upgrade of the treatment plant to reduce the effluent pollutant load led to the discharge limit for phenols being occasionally exceeded. The concern of the water authority prompted a study to investigate whether the toxicity of phenols could affect the performance of the receiving municipal wastewater treatment plant. To this end, mixtures of the industrial effluent and synthetic municipal wastewater were tested in a laboratory-scale activated sludge system. The bioreactor was fed with increasing ratios of the industrial wastewater in the combined influent (from 10 to 50%) over 7 months. No significant differences were observed in the system performance fed only with the synthetic wastewater (during the acclimation stage) or with the industrial wastewater. The bioreactor achieved average removal efficiencies of 70% for phenols even when half of the combined influent was the industrial wastewater. Bearing in mind the question of phenols, an important drawback was the high uncertainty in their determination by the conventional phenol index method due to the matrix effect. To overcome this a spectrophotometric procedure based on the serial dilutions of each pair of influent and effluent samples has been developed. Although strong microbial selection was observed by the changing bioreactor environment, the industrial effluent was found to be fully compatible with further treatment by conventional activated sludge process.

Biotransformation of Current-Use Progestin Dienogest and Drospirenone in Laboratory-Scale Activated Sludge Systems Forms High-Yield Products with Altered Endocrine Activity.

Dienogest (DIE) and drospirenone (DRO) are two fourth-generation synthetic progestins widely used as oral contraceptives. Despite their increasing detection in wastewaters and surface waters, their fate during biological wastewater treatment is unclear. Here, we investigated DIE and DRO biotransformation with representative activated sludge batch incubations and identified relevant transformation products (TPs) using high-resolution mass spectrometry. DIE exhibited slow biotransformation (16-30 h half-life) and proceeded through a quantitative aromatic dehydrogenation to form TP 309 (molar yields of ∼55%), an aromatic TP ∼30% estrogenic as 17β-estradiol. DRO experienced more rapid biotransformation (<0.5 h half-life), and 1,2-dehydrogenation formed the major TP 364 (molar yields of ∼40%), an antimineralocorticoid drug candidate named as spirorenone. Lactone ring hydrolysis was another important biotransformation pathway for DRO (molar yields of ∼20%) and generated pharmacologically inactive TP 384. Other minor pathways for DIE and DRO included hydroxylation, methoxylation, and 3-keto and C4(5) double-bond hydrogenation; distinct bioactivities are plausible for such TPs, including antigestagenic activity, antigonadotropic activity, and pregnancy inhibition effects. Thus, biotransformation products of DIE and DRO during wastewater treatment should be considered in environmental assessments of synthetic progestins, especially certain TPs such as the estrogenic TP 309 of DIE and the antimineralocorticoid spirorenone (TP 364) of DRO.

Impacts of solids retention time and antibiotic loading in activated sludge systems on secondary effluent water quality and microbial community structure.

Solids retention time (SRT) is one of the most important factors in designing and operating activated sludge systems for biological wastewater treatment. Longer SRTs have been shown to alter the structure and function of microbial communities, thereby leading to improved treatment efficacy with respect to bulk and trace organics, nutrient removal, and membrane fouling. Research has also shown that longer SRTs and/or higher influent antibiotic concentrations may lead to increased prevalence of antibiotic resistance. However, it is unclear whether elevated, yet subclinical, concentrations of antibiotics also impact the overall microbial community. The purpose of this study was to characterize changes in microbial community structure in a laboratory-scale activated sludge system as a function of SRT (2-20days) and influent concentrations (1×-100× ambient) of ampicillin, sulfamethoxazole, tetracycline, trimethoprim, and vancomycin. Changes in microbial community structure were evaluated based on 16S rRNA gene sequencing, and microbial community function was evaluated based on changes in effluent water quality, including attenuation of bulk and trace organics. The results confirmed that longer SRTs-but not antibiotic loadings-had a significant impact on microbial community structure and effluent water quality. Therefore, moderate spikes in influent antibiotic concentrations are not expected to adversely impact biological wastewater treatment. PRACTITIONER POINTS: Longer SRTs lead to changes in microbial community structure, including alpha and beta diversity and relative abundance of various taxa. Enhanced TOrC attenuation at longer SRTs may be linked to biomass abundance rather than changes in microbial community structure. Moderate spikes in influent antibiotic concentrations do not impact activated sludge performance or microbial community structure. The phyla Proteobacteria and Bacteroidetes comprise a majority of the microbial community in primary effluent and mixed liquor.

New insights in morphological analysis for managing activated sludge systems.

In activated sludge (AS) process, the impact of the operational parameters on process efficiency is assumed to be correlated with the sludge properties. This study provides a better insight into these interactions by subjecting a laboratory-scale AS system to a sequence of operating condition modifications enabling typical situations of a wastewater treatment plant to be represented. Process performance was assessed and AS floc morphology (size, circularity, convexity, solidity and aspect ratio) was quantified by measuring 100,000 flocs per sample with an automated image analysis technique. Introducing 3D distributions, which combine morphological properties, allowed the identification of a filamentous bulking characterized by a floc population shift towards larger sizes and lower solidity and circularity values. Moreover, a washout phenomenon was characterized by smaller AS flocs and an increase in their solidity. Recycle ratio increase and COD:N ratio decrease both promoted a slight reduction of floc sizes and a constant evolution of circularity and convexity values. The analysis of the volume-based 3D distributions turned out to be a smart tool to combine size and shape data, allowing a deeper understanding of the dynamics of floc structure under process disturbances.

Fate of fluorescent core-shell silica nanoparticles during simulated secondary wastewater treatment

Increasing use of silica nanoparticles (SiO2 NPs) in consumer products and industrial processes leads to SiO2 NP discharge into wastewater. Thus, there is a need to understand the fate of SiO2 NPs during wastewater treatment. However, the detection of SiO2 NPs in environmental systems is hindered by the elevated background levels of natural silicon. In this work, laboratory-synthesized fluorescent core-shell SiO2 NPs were used to study the fate of these NPs during secondary wastewater treatment. Fluorescent measurements provided an easy and fast method for SiO2 NP tracking. A laboratory-scale activated sludge system consisting of an aeration tank and a settler was fed with synthetic wastewater containing ca. 7.5 mg L−1 of fluorescent SiO2 NPs for 30 days. SiO2 NPs were effectively removed from the wastewater (>96%) during the first 6 days, however the concentration of SiO2 NPs in the effluent gradually increased afterwards and the NP discharge was as high as 65% of the input after 30 days of NP dosing. The poor removal of the SiO2 NPs was related to the high colloidal stability of the NPs in the wastewater and their limited propensity to biosorption. Although some degree of NP adsorption on the biomass was observed using fluorescence microscopy, the affinity of SiO2 NPs for the activated sludge was not enough for a sustained and effective removal of the SiO2 NPs from the wastewater.

Hephaestia caeni gen. nov., sp. nov., a novel member of the family Sphingomonadaceae isolated from activated sludge

A Gram-staining-negative, rod-shaped and motile bacterium, designated strain ERB1-3(T), was isolated from a laboratory-scale activated sludge system treating coke plant effluent using thiocyanate-supplemented growth medium. Strain ERB1-3(T) was oxidase-positive and weakly catalase-positive. The predominant fatty acids were C18:1ω7c (35.6 %) and C17:1ω6c (29.2%), and the major respiratory quinone was Q-10. Polar lipids were dominated by sphingoglycolipid and phosphatidylglycerol. Major polyamines were spermidine and sym-homospermidine. The G+C content of the genomic DNA of strain ERB1-3(T) was 66.4 mol%. Based on the 16S rRNA gene, strain ERB1-3(T) exhibited the highest sequence similarity values to Sphingomonas sanxanigenens DSM 19645(T) (96.1%), Sphingobium scionense DSM 19371(T) (95.1%) and Stakelama pacifica LMG 24686(T) (94.8%) within the family Sphingomonadaceae. The novel isolate had some unique chemotaxonomic features that differentiated it from these closely related strains, contained much more C17 : 1ω6c, C15 : 0 2-OH, C17:0 and C17:1ω8c fatty acids and possessed diphosphatidylglycerol only in trace amounts. On the basis of the phenotypic, chemotaxonomic and molecular data, strain ERB1-3(T) is considered to represent a novel genus and species, for which the name Hephaestia caeni gen. nov., sp. nov. is proposed. The type strain is ERB1-3(T) ( = DSM 25527(T) = NCAIM B 02511(T)).

Ottowia pentelensis sp. nov., a floc-forming betaproteobacterium isolated from an activated sludge system treating coke plant effluent

A Gram-negative-staining, short-rod-shaped, floc-forming bacterium, designated strain RB3-7(T), was isolated from a laboratory-scale activated sludge system treating coke plant effluent. Comparative analysis of the 16S rRNA gene sequence demonstrated that the novel isolate was distantly related (≤ 95.8 % similarity) to Ottowia thiooxydans K11(T) within the family Comamonadaceae. Strain RB3-7(T) was catalase- and oxidase-positive and non-motile. The predominant fatty acids were C₁₆:₀, cyclo C₁₇:₀, C₁₈:₁ω7c and C₁₆:₁ω7c, and the major respiratory quinone was Q-8. The G+C content of the genomic DNA of strain RB3-7(T) was 68.5 mol%. On the basis of phenotypic, chemotaxonomic and molecular data, strain RB3-7(T) is considered to represent a novel species of the genus Ottowia, for which the name Ottowia pentelensis sp. nov. is proposed. The type strain is RB3-7(T) ( = DSM 21699(T) = NCAIM B 02336(T)).

Coke Wastewater Treatment by a Three-Step Activated Sludge System

The treatment of industrial coke wastewater was studied in a laboratory-scale activated sludge system. The concentrations of the main pollutants in the wastewater ranged between 800 and 1870 mg COD/l, 100–221 mg phenols/l, 198–427 mg SCN/l, 133–348 mg $${\text{NH}}_4^ + - {{\text{N}} \mathord{\left/ {\vphantom {{\text{N}} {\text{l}}}} \right. \kern-\nulldelimiterspace} {\text{l}}}$$ and 11–41 mg CN−/l. To avoid inhibition phenomena resulting from the high concentrations of thiocyanate, ammonium nitrogen and cyanide a three-step process was implemented. The first step was anoxic for the removal of nitrates, followed by an oxic step during which biodegradation of phenols and thiocyanates took place, and by a second oxic step to oxidize ammonium nitrogen to nitrate. The dilution effect due to the recirculation of the final effluent to the head of the process and also, the separation of the nitrification step from the biodegradation of thiocyanate led to much higher efficiencies than when the process was carried out simultaneously. Very high removals were obtained (99% phenols, 97% SCN−, 63% COD, 98% $${\text{NH}}_4^ + - {\text{N}}$$ , 90% total-N and 99% cyanide) employing hydraulic residence times of 15.4 h for denitrification, 98 h for phenol and thiocyanate biodegradation and 86 h for nitrification.

Simulation of a coke wastewater nitrification process using a feed-forward neuronal net

A laboratory-scale Activated Sludge System (ASS) was employed for the biodegradation of coke wastewater, which contains high concentrations of ammonium, thiocyanate, phenols and other organic compounds. The well-known kinetics models of Monod or Haldane are not very useful due to inhibition phenomena amongst the pollutants and also, they need the determination of a wide range of parameters to be introduced in the models. In this paper, a feed-forward neural network is outlined to obtain a satisfactory approach for estimating the effluent ammonium concentration of the treatment plant. The methodology consists in performing several tests with a group of different sizes of the hidden layer and different subsets of input variables. The developed model is useful to obtain simulations under different conditions of the influent stream, thus enabling the effluent ammonium concentration to be estimated. This neural network achieves better results than classical mathematical models for biological wastewater treatment as a result of the complex composition of the coke wastewater.

Properties of Four Biological Flocs as Related to Settling

The influence of four industrial wastewater types (organic chemical, dye, leather, and winery industries) on the exopolymeric substances (EPSs) constituents [protein, polysaccharide, and deoxyribonucleic acid (DNA)] and physicochemical properties of flocs (contact angle, surface charge, and bound water) was determined. Four laboratory scale activated sludge systems were used; they were fed with real wastewaters and were operated continuously under steady-state conditions. The EPS analysis showed that between 70 and 80% of the extracellular organic material could be attributed to protein. The proteins in the bound form were quantitatively greater than the soluble protein form in winery industry floc EPSs. The soluble protein ratios were higher than bound protein ratios in organic chemical, dye, and leather industries flocs. Lower amounts of protein and high DNA content were found in the EPS flocs grown on wastewaters containing more complex substrates (organic chemical, leather, and dye). Changing the wastewater from chemical, leather, and dye to that of winery industry resulted in an increase in protein and a decrease in DNA level of floc EPSs. The sludge surface of winery industry flocs were less hydrophobic (small contact angle) and more highly negatively charged compared to chemical, dye, and leather industry flocs. A higher sludge volume index (SVI), an indication of poorer settleability, was associated with both small amounts of EPS and protein and a high amount of DNA. Both high hydrophilic and negatively charged surfaces corresponded to lower levels of SVI and good settling properties. The results of this study demonstrated that wastewater type influenced the EPS composition and physicochemical properties of sludge. The surface properties (surface charge, contact angle, and bound water) and composition of EPS, apart from the carbohydrate content, governed the settleability of sludge and were important in controlling the SVI.

Investigation of OUR and NUR experiments for nitrogen and phosphorus removal with activated sludge: a lab-scale study

Activated sludge systems are widely used in wastewater treatment. Organic carbon removal and nutrient removal are important for stringent water discharge standards. Therefore, activated sludge systems are widely used to remove carbon, nitrogen and phosphorus in new wastewater treatment systems or upgrades of existing systems. The determination of system compounds and kinetic parameters for modelling of these systems are important. For this purpose, respirometric measurements are used to reveal the electron consumption rate of biomass. In order to determine OUR (oxygen uptake rate) and NUR (nitrate uptake rate) parameters, a laboratory scale activated sludge system, including anaerobic, anoxic and aerobic zones, was developed. The performance of the system was continuously controlled from influent and effluent samples. OUR and NUR measurements indicated the kind of nitrogen-phosphorus removal systems required. Moreover, phosphorus uptake in the anoxic zone was investigated. It was found that phosphorus uptake in the anaerobic zone was related to substrate type consumed biologically. The OUR and NUR were found to be lower than in continuous activated sludge measurements. This may be because the mixed culture of the system affected the system performance, owing to competition between denitrification bacteria and poly-P bacteria.

Water and wastewater management in the Przyjazn Coking Plant in Dabrowa Gornicza

A laboratory-scale Activated Sludge System (ASS) was employed for the biodegradation of coke wastewater, which contains high concentrations of ammonium, thiocyanate, phenols and other organic compounds. The well-known kinetics models of Monod or Haldane are not very useful due to inhibition phenomena amongst the pollutants and also, they need the determination of a wide range of parameters to be introduced in the models. In this paper, a feed-forward neural network is outlined to obtain a satisfactory approach for estimating the effluent ammonium concentration of the treatment plant. The methodology consists in performing several tests with a group of different sizes of the hidden layer and different subsets of input variables.The developed model is useful to obtain simulations under different conditions of the influent stream, thus enabling the effluent ammonium concentration to be estimated. This neural network achieves better results than classical mathematical models for biological wastewater treatment as a result of the complex composition of the coke wastewater.

Effects of Chemical Uncouplers on Microbial Biomass Production, Metabolic Activity, and Community Structure in an Activated Sludge System.

Recent reports have suggested the usefulness of a metabolic uncoupler to reduce excess sludge production in the activated sludge process. This study was conducted to more thoroughly study the effects of different chemical uncouplers on microbial biomass production, metabolic activity, and community structure in a laboratory-scale activated sludge system fed with synthetic sewage. Results showed that the amount of biomass produced decreased sharply with increasing concentrations of uncouplers in all cases. Among the five congeners of chlorophenols and nitrophenols as uncouplers studied, 4-nitrophenol was the most effective in reducing biomass production. The addition of 200 μM 4-nitrophenol resulted in a reduction in the biomass yield to less than 10% compared the control culture without the additive, while the BOD removal efficiency with the uncoupler remained approximately 80% of the control level. Differences in biomass reduction efficiency among the uncouplers tested suggested that uncouplers with a lower pKa value have a higher potential to reduce biomass production. A short-term sequencing batch cultivation of sludge with any uncoupler exerted no or little effect on respiratory enzyme activities and the microbial community structure of the sludge. When the inhibitory effect of 4-nitrophenol on biomass production was studied in prolonged sequencing batch cultures, it was found to gradually diminish with time and had almost vanished after 4 weeks of operation. At this stage, a significant change in microbial community structure was demonstrated by respiratory quinone profiling. These results indicate that dosing an uncoupler in a short period is useful for minimizing excess sludge production in the activated sludge process without a significant decrease in BOD removal efficiency, but this positive effect is questionable over a long period of operation.

Examination of three theories for mechanisms of cation-induced bioflocculation

Research from different studies has been used to support three different theories pertaining to the role of cations in bioflocculation. These theories are the alginate theory, Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory, and divalent cation bridging (DCB) theory. The objectives of this research were to examine the role of cations in bioflocculation to determine which theory, if any, best describes cation induced bioflocculation. Experiments were performed using laboratory scale activated sludge systems with bactopeptone as a feed. The feed was supplemented with either calcium, magnesium, or sodium at increasing concentrations. Floc properties were analyzed in each reactor during steady state periods. The addition of calcium or magnesium to the feed individually resulted in improvements in SVI, CST, SRF, cake solids and floc strength and each of these divalent cations produced similar results. The addition of sodium to the feed resulted in a deterioration in floc properties relative to a control reactor. Analysis of these results suggest that the DCB theory best explains the role of cations. The discrepancies between different studies were examined and are thought to be a result of different experimental procedures in different studies and in particular the use of short-term batch tests versus continuous flow reactor studies. In addition, the implications of DCB theory suggests that activated sludge systems should attempt to lower the ratio of monovalent to divalent cations to improve floc properties and treatment performance.

Biological Treatment of Petrochemical Wastewaters by Pseudomonas Sp. Added Activated Sludge Culture

Pseudomonas sp. isolated from the activated sludge of a petrochemical industry treatment plant was harvested and used as an inoculum culture for biological treatment of petrochemical wastewaters. The objective was the comparison of biological treatment efficiencies between Pseudomonas sp. added activated sludge and normal activated sludge taken from the full scale treatment plant. Experiments were carried out both in batch and continuous operations using a laboratory scale activated sludge system. Monod kinetic was used to determine kinetic coefficients from the experimental data of continuous operations. The maximum COD utilization rate constant (k), saturation constant (Ks), microbial decay rate (kd), yield coefficient (Y) and maximum specific growth rate (μmax) were determined to be 0.95 1/day, 199 mgCOD/L, 0.10 1/day, 0.30 mgMLSS/mgCOD and 0.285 1/day for normal activated sludge, respectively. These coefficients were also determined for Pseudomonas sp. added activated sludge system as 2.75 1/day, 1035 mgCOD/L, 0.08 1/day, 0.32 mgMLSS/mgCOD and 0.88 1/day, respectively. Removal efficiencies of COD, TN and phenol for lower sludge ages were found higher for the Pseudomonas sp. added activated sludge system than that of the activated sludge system. Treatment efficiencies were found to be almost the same for both systems at high sludge ages.

COD and nitrogen mass balances in activated sludge systems

COD and nitrogen balances were performed on four different types of laboratory-scale activated sludge system: aerobic, anoxic, anoxic-aerobic and anaerobic-anoxic-aerobic (biological excess phosphorus removal systems). The systems included a variety of configurations, with differing wastewater characteristics and operating parameters. The results suggest that good COD balances are to be expected in aerobic and anoxic-aerobic systems. Systems incorporating anaerobic zones exhibit low COD balances (less than 80%). Fermentation in the anaerobic zone apparently is implicated in this “loss” of COD. The consequences of the COD “loss” include both a significant decrease in oxygen requirements and in sludge production compared to aerobic or anoxic-aerobic systems. Possible mechanisms for the loss of COD and areas which require further study are discussed.

Microbial degradation of acrylonitrile waste effluents: the degradation of effluents and condensates from the manufacture of acrylonitrile

Effluents from the manufacture of acrylonitrile are difficult to biodegrade. They contain eight major organic components: acrylonitrile, acrylamide, acrylic acid, acrolein, cyanopyridine, fumaronitrile, succinonitrile and maleimide. Bacteria have been isolated that grow on acrylonitrile, acrylamide, acrylic acid, cyanopyridine or succinonitrile as the sources of carbon and nitrogen, or which can biotransform acrolein, fumaronitrile or maleimide. Mixed cultures of the bacteria were grown in mixed batch and continuous culture on the eight major components of the waste, and complete degradation of all the components was demonstrated (Wyatt & Knowles, Biodegradation, 6, 93–107, 1995). Effluents from Stripper Column Bottoms (SCB) from acrylonitrile (AN) manufacture were biodegraded by continuous mixed cultures of the bacteria, with a 75% reduction in Chemical Oxidation Demand (COD) and over 99% removal of detectable toxic components of the wastes. Effluents from Wastewater Column Bottoms (WWCB) from AN manufacture, which are stronger than the SCB effluents, were more resistant to biodegradation and had to be diluted 10-fold to enable 75% removal of COD but with a low biomass yield in the fermenter. Condensates of the WWCB and SCB were prepared by distillation to decrease the ammonia and tar content. The mixed bacterial continuous culture, as obtained in the earlier studies, was able to degrade the WWCB condensate, reducing the COD by 80%. The SCB condensate could also be biodegraded in continuous culture, with removal of 90% of the COD. In both cases the microbial culture became floccular. A mixed condensate of the AN wastes was prepared by employing a recycle system on the AN manufacturing plant, to reduce the levels of ammonia and cyanide in the effluent. A mixed bacterial continuous culture, prepared as previously, reduced the COD from 3600 to 850–900 ppm, and removed cyanide and all detectable toxic components of the effluent. A two-stage laboratory-scale activated sludge system was used to degrade the mixed condensate. The process was floccular, and a biomass recycle was employed. Overall, a reduction in COD of 80% was obtained, but no nitrification was observed in this simple system. Gel filtration studies of the residual COD showed that it had a molecular weight of greater than 700, and was probably due to polymerization of monomeric material present in the effluents caused by their storage prior to biotreatment.

Incidence of Sphaerotilus Natans in Laboratory Scale Activated Sludge Systems

Bulking in activated sludge systems due to proliferation of Sphaerotilus natans is very common in laboratory-scale but rare in full-scale systems. From two laboratory-scale studies it is concluded that a cause for proliferation was attached growth of S.natans on the walls of the feed lines and reactor surfaces continuously seeding the mixed liquor. It is suggested that S.natans bulking in laboratory-scale systems is common compared to full-scale systems because the surface area/volume ratio of the former is orders of magnitude higher than that of the latter so that the potential for seeding from attached growths in laboratory-scale plants is correspondingly higher. It would appear that in laboratory-scale activated sludge systems regular cleaning of the feed lines and daily scrubbing of the reactor and other wetted surfaces will eliminate S.natans bulking due to seeding of the mixed liquor from these surfaces.

Experiments with an Adaptive-Questing Computer Control Strategy for the Biological Oxidation of Inhibitory Substrates

The response of a laboratory scale activated sludge system to an inhibitory substrate, phenol, was studied using oxygen uptake rate, which proved to be a rapidly responding and easily measurable metabolic activity parameter. This parameter was used in the design of a control strategy to manipulate the flow rate of the inhibitory substrate feed stream in such a manner that the substrate uptake rate could be maintained near maximum under conditions of changing inlet concentration and reaction biomass. Measurements of oxygen uptake rate as a function of inhibitory substrate concentration indicated that oxygen uptake rate depended on the adaptation of the culture to the substrate, in this case phenol. For partially and fully adapted systems, oxygen uptake rate increased rapidly as the substrate concentration increased till the maximum was reached at ca. 4 mg/lt. Further increases in substrate concentration led to a linear decrease in oxygen uptake rate to a maximum inhibition level at 300 mg/lt. Since inhibitory effects occurred at low phenol concentrations, stopping the phenol flow rate upon detection of inhibition led to rapid consumption of accumulated phenol. System recovery could be detected by a sudden peak in oxygen uptake rate, which occurred when the phenol concentration approached zero. Two strategies for controlling the feed flow rate were developed: one utilizing a process mass balance model with constant yield coefficient, and the other utilizing an adaptive-questing strategy to manipulate the feed rate according to trends in the oxygen uptake rate. The second strategy proved to be superior and the reactor could be controlled under conditions of changing feed concentrations, so that nearly maximum uptake rates were achieved.

Parameters affecting protein production from brewery waste water in a multi-channel laboratory-scale activated sludge system

With the aim of studying the possible utilization of brewery waste water activated sludge for animal feeding, the influence of the solids retention time (SRT) and nitrogen supplementation were investigated, especially with respect to biomass production and biomass composition. It was found that the SRT strongly influenced both parameters. At an SRT of from 4 to 6 days excellent biomass production was obtained. This biomass had the highest protein content and the daily protein production was four times higher than at a SRT of 20 days. Supplementation with urea doubled the protein production, lowered the carbohydrate and poly-β-hydroxybutyric acid content, but increased the nucleic acid content. The COD removal was better and phosphorus removal increased. In order to study these variables, a multi-channel laboratory system was designed. Because of its simplicity in operation and its versatility this system is described in detail.