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In this study, three sequencing batch biofilter granular reactors (SBBGRs) were employed to treat model lignin wastewater containing different lignin models (2,6-dimethoxyphenol, 4-methoxyphenol, and vanillin). After 40 days of cultivation, uniform-shaped aerobic granular sludge (AGS) was successfully developed through nutrient supplementation with synthetic wastewater. During the acclimation stage, the chemical oxygen demand (COD) reduction efficiencies of the three reactors showed a trend of initial decreasing (5-20%) and then recovering to a high reduction efficiency (exceeding 90%) in a short period of time. During the stable operation stage, all three reactors achieved COD reduction efficiencies exceeding 90%. These findings indicated the cultivated AGS's robust resistance to changes in lignin models in water. UV-Vis spectra analysis confirmed the effective degradation of the three lignin models. Microbiological analysis showed that Proteobacteria and Bacteroidetes were always the dominant phyla. At the genus level, while Acinetobacter (15.46%) dominated in the inoculation sludge, Kapabacteriales (7.93%), SBR1031 (11.77%), and Chlorobium (25.37%) were dominant in the three reactors (for 2,6-dimethoxyphenol, 4-methoxyphenol, and vanillin) after degradation, respectively. These findings demonstrate that AGS cultured with SBBGR effectively degrades lignin models, with different dominant strains observed for various lignin models., Competing Interests: The authors declare there is no conflict., (© 2024 The Authors This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/).)

Although submerged membrane bioreactor (MBR) are widely used in treating municipal wastewater and recovery of potential resources, membrane operational parameters and membrane fouling control remain debated issues. In this study, the treatment of municipal wastewater by MBR at high-biomass sludge (MLSS (g/L) ranging from 5.4 g/L to 16.1 g/L) was assessed at an organic loading rates (OLRs) ranging from 0.86 to 3.7 kg COD/m 3 d. The correlation between trans-membrane pressure and total fouling resistance was thoroughly investigated in this study. According to the findings, greater OLRs of 0.86 to 3.7 kg COD/m 3 d caused a decrease in COD, BOD, and NH 4 -N removal efficiency, and higher OLRs of 3.7 kg COD/m 3 d resulted in a higher increase in total fouling resistance (R t ). The economic study of using the MBR system proved that for a designed flow rate of 20 m 3 /d, the payback period from using the treated wastewater will be 7.98 years, which confirms the economic benefits of using this MBR for treating municipal wastewater. In general, understanding the challenges facing the efficiency of MBR would improve its performance and, consequently, the sustainability of wastewater reclamation., (© 2023. Springer Nature Limited.)

This study aimed to explore how dissolved oxygen (DO) affected the characteristics and mechanisms of denitrification in mixed bacterial consortia. We analyzed denitrification efficiency, intracellular nicotinamide adenine dinucleotide (NADH), relative expression of functional genes, and potential co-occurrence network of microorganisms. Results showed that the total nitrogen (TN) removal rates at different aeration intensities (0.00, 0.25, 0.63, and 1.25 L/(L·min)) were 0.93, 1.45, 0.86, and 0.53 mg/(L·min), respectively, which were higher than previously reported values for pure culture. The optimal aeration intensity was 0.25 L/(L·min), at which the maximum NADH accumulation rate and highest relative abundance of napA, nirK, and nosZ were achieved. With increased aeration intensity, the amount of electron flux to nitrate decreased and nitrate assimilation increased. On one hand, nitrate reduction was primarily inhibited by oxygen through competition for electron donors of a certain single strain. On the other hand, oxygen was consumed rapidly by bacteria by stimulating carbon metabolism to create an optimal denitrification niche for denitrifying microorganisms. Denitrification was performed via inter-genus cooperation (competitive interactions and symbiotic relationships) between keystone taxa (Azoarcus, Paracoccus, Thauera, Stappia, and Pseudomonas) and other heterotrophic bacteria (OHB) in aeration reactors. However, in the non-aeration case, which was primarily carried out based on intra-genus syntrophy within genus Propionivibrio, the co-occurrence network constructed the optimal niche contributing to the high TN removal efficiency. Overall, this study enhanced our knowledge about the molecular ecological mechanisms of aerobic denitrification in mixed bacterial consortia and has theoretical guiding significance for further practical application., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

This study focused on using pH as a single indicator to evaluate/control the performance of the nitritation system under the influence of three major operational parameters, and a total of fifteen batch tests were conducted. Results indicated that there were important interactions among different operational parameters and pH in the nitritation system; it was possible to propose the optimal nitritation operation scheme to compensate for negative changes in operational parameters. The optimal carbon to nitrogen (C/N) ratio was kept at 2.0 to ensure efficient removal of ammonium. The reaction time was the lowest (150 min) with the temperature = 20 °C, C/N = 0, and sludge/water ratio = 1:1. However, the C/N ratio could be adjusted to close to zero by reducing the temperature to about 10 °C, weakening the heterotrophic bacteria, and supplying sufficient biomass. The C/N ratio and sludge/water ratio could also be set at 4.0 and 1:3 respectively to deal with the impact of low temperature and organic matter. Results of this study might be useful to explain the optimal conditions and process control schemes with pH as a single indicator.

Optimal operation of membrane bioreactor (MBR) plants is crucial to save operational costs while satisfying legal effluent discharge requirements. The aeration process of MBR plants tends to use excessive energy for supplying air to micro-organisms. In the present study, a novel optimal aeration system is proposed for dynamic and robust optimization. Accordingly, a deep reinforcement learning (DRL)-based optimal operating system is proposed, so as to meet stringent discharge qualities while maximizing the system's energy efficiency. Additionally, it is compared with the manual system and conventional reinforcement learning (RL)-based systems. A deep Q-network (DQN) algorithm automatically learns how to operate the plant efficiently by finding an optimal trajectory to reduce the aeration energy without degrading the treated water quality. A full-scale MBR plant with the DQN-based autonomous aeration system can decrease the MBR's aeration energy consumption by 34% compared to other aeration systems while maintaining the treatment efficiency within effluent discharge limits.

Hysteresis effect on backwashing in a submerged MBR was investigated with dead-end hollow fiber membranes. The out-of-step changes in TMP and flux is the real hysteresis effect which is common but easily overlooked. Methods of visualization and ultrasonic spectrum analysis were implemented. The results showed that fouling layer is just the culprit of hysteresis effect. Fouling level and fiber length were determined as two key factors that affect hysteresis effect by data and model derivation. Moreover, a hysteresis evaluation index "τ bw " is proposed to quantify the result of TMP vs time. The relationship between influence factors and "τ bw " is interactive. A linear relationship between fouling level and "τ bw " was found as well as an extreme value between fiber length and "τ bw ". A lower fouling level (lower backwashing flow) and optimal backwashing duration will be helpful for an effective backwashing no matter for membrane fouling control or energy cost reduce., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

As a host for therapeutic protein expression, Chinese hamster ovary (CHO) cells are widely utilized in the mainstream biopharmaceutical industry. Cell culture process development plays an important role in transitioning laboratory research to manufacturing. Among different mathematic tools, kinetic modeling is commonly achieved through analyzing cell culture data to design process parameters, optimize media, and scale up bioreactors. In this review, we examine key factors for upstream process development, and summarize currently used kinetic modeling strategies. In addition, two original examples of kinetic modeling application optimizing cell culture performance are presented. A comprehensive understanding is provided for the kinetic modeling and its applications in cell culture process development.

Secondary effluent from paper mill was characterized by poor biodegradability and containing recalcitrant compounds. In this study, four bioreactors, including a sequencing batch biofilm reactor (SBBR), a stirred-tank reactor (STR) and two submerged aeration reactors (SAR) were used to treat secondary effluent from a recycled paper mill respectively. The results indicated that chemical oxygen demand (COD) was increased by SAR2 treatment and COD removal efficiency for SBBR, SAR1 and STR was 39.7%, 15.7% and 30.9% respectively. It is suggested that recalcitrant compounds were removed by SBBR, SAR1 and STR respectively. Total nitrogen (TN) and total phosphorus (TP) of wastewater were increased by treatments of each bioreactor, which suggested that endogenous respiration of biomass occurred during the treatment. Microbial analysis of sludge from different bioreactors suggested that the removal of recalcitrant compounds in SBBR and STR might be related to the presence of unique microorganisms in each reactor., (Copyright © 2019 Elsevier B.V. All rights reserved.)

An efficient emulsion microreactor was constructed for selective conversion of lignosulfonate via hydrogen transfer reaction based on the self-surfactivity of this natural aromatic polymer. Industrial Raney Ni and isopropanol were used as catalyst and hydrogen donor, respectively. The results showed that the emulsion microreactor has a remarkable process intensification effect on the lignosulfonate depolymerization. Under mild condition of 473 K for 2.0 h, 116.1 mg g -1 of volatile phenolic monomer can be obtained, which is twice of that from other investigated processes without emulsion of this work. In particular, 39.3 mg g -1 of which is composed of 4-ethyl guaiacol, an important and versatile chemical currently from petrochemical industry. Furthermore, the solvent separates to two phases automatically after reaction due to the consumption of lignosulfonate, which makes handy products enrichment and separation. Additionally, the emulsion microreactor is significantly affected by hydrogen donor and is efficient for other lignin sources as well., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study undertakes a state-of-the-art review on thermophilic membrane bioreactors (ThMBRs). Thermophilic aerobic membrane bioreactors (ThAeMBR) and thermophilic anaerobic membrane bioreactors (ThAnMBR) have been widely tested for various high-temperature industrial wastewater treatments at lab- and pilot-scale studies and full-scale applications. The biological and membrane performances of the ThAeMBRs and ThAnMBRs could be better, comparable or poorer, as compared to the mesophilic ones. In general, sludge yield was much lower, biodegradation kinetic was higher, and microbial community was less diversity in the ThAeMBR and ThAnMBR systems. The results from the literature show that ThMBR technology has demonstrated many advantages and is a promising technology for industrial wastewater treatment and sludge digestion. Furthermore, challenges and opportunities of various ThMBRs for industrial applications are identified and discussed., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Co-production of glucose, furfural and other green materials based on a lignocellulosic biorefinery is a promising way to realize the commercial application of corncob residues. An effective process was developed for glucose production using low temperature bisulfite pretreatment and high-solids enzymatic hydrolysis. Corncob residues from furfural production (FRs) were pretreated with 0.1g NaHSO 3 /g dry substrate at 100°C for 3h. Lignin was sulfonated and sulfonic groups were produced during pretreatment, which resulted in decreasing the zeta potential of the samples. Compared with raw material, bisulfite pretreatment of FRs increased the glucose yield from 18.6 to 99.45% after 72h hydrolysis at a solids loading of 12.5%. The hydrolysis residues showed a relatively high thermal stability and concentrated high derivatives. Direct pretreatment followed by enzymatic hydrolysis is an environmentally-friendly and economically-feasible method for the production of glucose and high-purity lignin, which could be further converted into high-value products., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Oleanolic (OA) and ursolic acid (UA) are plant secondary metabolites with diverse pharmacological properties. To reach reasonable productivities with plant cell suspension cultures, elicitation is a widely used strategy. Within the presented work, the effects of different elicitors on growth and production of OA and UA in a Salvia fruticosa cell suspension culture were examined. Beside commonly used elicitors like jasmonic acid (JA) and yeast extract, the influence of medium filtrates of the endophytic fungi Aspergillus niger and Trichoderma virens was investigated. The best eliciting effects were achieved with JA and fungal medium filtrates. Both increased the triterpene content by approximately 70 %. Since JA showed significant growth inhibition, the volumetric triterpene yield did not increase. But, adding fungal filtrates increased the volumetric triterpene yield by approximately 70 % to 32.6 mgOA l(-1) and 65.9 mgUA l(-1) for T. virens compared to the control with 19.4 mgOA l(-1) and 33.3 mgUA l(-1). An elicitation strategy combining fungal medium filtrate of T. virens with sucrose feeding significantly enhanced cell dry weight concentration to 22.2 g l(-1) as well as triterpene content by approximately 140 %. In total, this led to an approximately 500 % increase of volumetric triterpene yield referring to the control with final values of 112.9 mgOA l(-1) and 210.4 mgUA l(-1). Despite the doubled cultivation duration, productivities of 6.7 mgOA l(-1) day(-1) and 12.4 mgUA l(-1) day(-1) were reached. These results demonstrate methods by which increased productivities of triterpenes can be achieved to attain yields competing with intact plants.

This paper critically reviews the impacts of supplementing trace elements on the anaerobic digestion performance. The in-depth knowledge of trace elements as micronutrients and metalloenzyme components justifies trace element supplementation into the anaerobic digestion system. Most of the earlier studies reported that trace elements addition at (sub)optimum dosages had positive impacts mainly longer term on digester stability with greater organic matter degradation, low volatile fatty acids (VFA) concentration and higher biogas production. However, these positive impacts and element requirements are not fully understood, they are explained on a case to case basis because of the great variance of the anaerobic digestion operation. Iron (Fe), nickel (Ni) and cobalt (Co) are the most studied and desirable elements. The right combination of multi-elements supplementation can have greater positive impact. This measure is highly recommended, especially for the mono-digestion of micronutrient-deficient substrates. The future research should consider the aspect of trace element bioavailability., (Copyright © 2016. Published by Elsevier Ltd.)

Anaerobic ammonium oxidation (anammox) has been proved to be a promising nitrogen removal method for treating ammonium-rich wastewater. However, because of the low-growth rate of anammox bacteria, maintenance of a sufficient amount of anammox biomass in reactor became a key factor in application. Gel immobilization is an efficient method to prevent biomass from being washed out and to promote hyper-concentrated cultures. This study focused on a nitrogen removal process by anammox enrichment culture immobilized in polyvinyl alcohol and sodium alginate (PVA-SA) gel beads. The rapid startup of reactor demonstrated that gel entrapment was supposed to be a highly effective technique for immobilizing anammox bacteria. The anammox bacteria present in the enrichment were identified to be Jettenia-like species (>98%). Moreover, the effect of hydraulic retention time (HRT), pH, and temperature on immobilized anammox processes were investigated. The effect of pH and temperature on the anammox process was evidently weakened in PVA-SA immobilized gel beads, however, the effect of HRT on the anammox reaction was enhanced. Therefore, a stable operated reactor could be obtained in an anaerobic sequencing batch reactor, which proved gel immobilization was an excellent method to maintain the biomass in anammox reactor for application.

Filamentous fungi are widely used to produce cellulase, but how the fermentation conditions affect their production is not well known. In this study, cellulase production by Trichoderma viride in submerged fermentations with free cells in a stirred-tank reactor (STR) and immobilized cells in a rotating fibrous-bed bioreactor (RFBB) were investigated. Compared to free-cell fermentation, immobilized-cell fermentation gave 35.5% higher FPase activity and 69.7% higher saccharification yield of sugarcane bagasse (SCB). The secretory proteins in the fermentation broths were analyzed with two-dimensional gel electrophoresis (2-DE) and MALDI-TOF-TOF mass spectrometry, which identified 24 protein spots with differential expression levels. Among them, cellobiohydrolase CBH II and endoglucanase EG II were highly expressed and secreted in the immobilized-cell fermentation, while the free-cell fermentation produced more CBH І and EG ІV. These results showed that immobilized-cell fermentation with T. viride in the RFBB was advantageous for cellulase production., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A fermentation process using Clostridium tyrobutyricum immobilized in a fibrous-bed bioreactor (FBB) was developed for butyric acid production from sugarcane bagasse (SCB) hydrolysate. SCB was first treated with dilute acid and then hydrolyzed with cellulases. The hydrolysate containing glucose and xylose was used as carbon source for the fermentation without detoxification. The bacterium was able to grow at a specific growth rate of ∼0.06 h(-1) in media containing 15-20% (w/v) SCB in serum bottles. In batch cultures in the FBB, both glucose and xylose in the SCB hydrolysate were simultaneously converted to butyrate with a high yield (0.45-0.54 g/gsugar) and productivity (0.48-0.60 g/Lh). A final butyrate concentration of 20.9 g/L was obtained in a fed-batch culture, with an overall productivity of 0.51 g/Lh and butyrate yield of 0.48 g/g sugar consumed. This work demonstrated the feasibility of using SCB as a low-cost feedstock to produce butyric acid., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A liquid marble micro- bioreactor is used to conduct blood typing as a typical biological assay. This study portrays the potential of using such microreactors for biochemical and biological analysis., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An adaptive network based fuzzy inference system (ANFIS) model was employed to predict effluent chemical oxygen demand (COD(eff)) and ammonia nitrogen (NH(4)(+) (eff)) from an anaerobic/anoxic/oxic (A(2)/O) process, and meanwhile a self-adapted fuzzy c-means clustering algorithm was used to identify the model's architecture and optimize fuzzy rules. When constructing the model or predicting, the on-line monitoring parameters, namely hydraulic retention time (HRT), influent pH (pH), dissolved oxygen in the aerobic reactor (DO) and mixed-liquid return ratio (r), were adopted as the input variables. Compared with the artificial neural network (ANN) model whose weight vector was optimized by a real-code genetic algorithm (GA), the ANFIS presented better estimate performance. When predicting, the mean absolute percentage errors (MAPEs) of 1.8458% and 2.8984% for COD(eff) and NH(4)(+) (eff) could be achieved using ANFIS; the root mean square errors (RMSEs) for COD(eff) and NH(4)(+) (eff) were 1.6317 and 0.1291, respectively; the correlation coefficient (R) values of 0.9928 and 0.9951 for COD(eff) and NH(4)(+) (eff) could also be achieved. The results indicated that reasonable monitoring A(2)/O process performance, just using on-line monitoring parameters, has been achieved through the ANFIS.

Hemicellulose is a potential by-product currently under-utilized in the papermaking industry. It is a hetero-carbohydrate polymer. For hardwood hemicelluloses, D-xylose is the major component upon depolymerization. At SUNY-ESF, wood extracts were obtained by extracting sugar maple wood chips with hot water at an elevated temperature. The wood extracts were then concentrated and acid hydrolyzed. Ethanologenic bacteria, E. coli FBR5, had a good performance in pure xylose medium for ethanol production. However, FBR5 was strongly inhibited in dilute sulfuric acid hydrolyzate of hot-water wood extract. FBR5 was challenged by hot-water wood extract hydrolyzate in this study. After repeated strain adaptation, an improved strain: E. coli FBHW was obtained. Fermentation experiments indicated that FBHW was resistant to the toxicity of hydrolyzate in the fermentation media of concentrated hydrolyzate, and xylose was completely utilized by the strain to produce ethanol. FBHW was grown in the concentrated hydrolyzate without any detoxification treatment and has yielded 36.8g/L ethanol., (Copyright 2010 Elsevier Inc. All rights reserved.)

Batch experiments were conducted on the degradation of synthetic and municipal wastewater by six different strains, i.e., Agrobacterium sp., Bacillus sp., Enterobacter cloacae, Gordonia, Pseudomonas stutzeri, Pseudomonas putida. By applying a fractional factorial design (FFD) of experiments, the influence of each strain and their interactions were quantified. An empirical model predicting the treatment efficiency was built based on the results of the FFD experiments with an R(2) value of 99.39%. For single strain, Enterobacter cloacae, Gordonia and P. putida (p=0.008, 0.009 and 0.023, respectively) showed significant enhancement on organic removal in the synthetic wastewater. Positive interaction from Enterobacter cloacae, Gordonia (p=0.046) was found, indicating that syntrophic interaction existed, and their coexistence can improve total organic carbon (TOC) degradation. Verification experiments were performed to evaluate the effect of bioaugmentation by introducing three selected strains into an activated sludge reactor for treating municipal wastewater. The removal efficiency of TOC with the bioaugmentation was increased from 67-72% to 80-84% at an influent TOC concentration of 200mg/L. The results derived from this study indicate that the FFD is a useful screening tool for optimizing the microbial community to enhance treatment efficiency.

Coupled granules are self-immobilized aggregates of microorganisms under micro aerobic conditions, which have the dissolved oxygen (DO) level of 0.6 mg.L(-1). The effects of DO concentration on pentachlorophenol (PCP) reduction and its microbial community were investigated in a coupled anaerobic and aerobic reactor. Both the diversity and the dynamicity of the Eubacteria and Archaea community, which were responsible for PCP degradation, were evaluated by means of amplification by polymerase chain reaction (PCR) and separation using the denaturing gradient gel electrophoresis (DGGE) technique. The results demonstrated a major shift in the Eubacteria and Archaea community as the mixed aerobic and anaerobic seeding sludge (1:1 by volume) developed into coupled granules and finally acclimated with PCP throughout the experiment period within 60 days. The numbers of the Eubacteria population decreased from 20, 16 to 11; Shannon diversity index decreased from 2.75, 2.53 to 2.10. In contrast, the number of the Archaea population increased from 12, 14 to 18; and Shannon diversity index increased from 1.87, 1.88 to 2.43. Phylogenetic analysis based on 16SrDNA genes showed the dominance Sphingomonas, Desulfobulbus, Proteobacteria, Actinobacterium, Methanogenic and some uncultured bacteria in the PCP-degrading coupled granules. Microorganism community construction of coupled granules was also deduced.

A model was developed, based on the power law of growth and Avrami's concepts in nuclei growth to describe the heterogeneous nature of alkaline pulping kinetics, taking into account the effects of effective alkali concentration and temperature. It was then applied against published data to estimate model parameters. The final form of the model applied to alkaline pulping of thin hemp woody core in flow-through reactors could be represented by a first order rate equation with a time-dependent rate constant: [-dY/dt = A.[OH-]b.exp (-E/RT)n.Y.t(n-1). The rate equations applied for delignification, cellulose and xylan losses. It was found that the heterogeneous kinetic models predicted well the delignification and xylan loss of hemp woody core, with R2 values of 0.96 and 0.97, respectively. The model was, however, less accurate in predicting cellulose loss. The values n, which could represent the acceleration/deceleration extent of growth of reacting volumes, were found to be less than unity. This demonstrated the heterogeneous characteristics of alkaline pulping for hemp woody core.

In this study, the mass transfer coefficient of biological floc (K(L)a(bf)) was estimated from the mass transfer coefficient of the mixed-liquor (K(L)a(f)) and the reactor-solution (K(L)a(e)). The biological floc resistance (BFR) and reactor-solution resistance (SR) were defined as the reciprocal of K(L)a(bf) and K(L)a(e), respectively, by applying the concept of serial-resistance originally presented in two-film theory (Lewis and Whitman (1924) Ind Eng Chem 16:1215-1220). The specific biological floc resistance (SBFR) was defined as biological floc resistance per unit biomass concentration. The data indicated that an activated sludge process yielding low BFR/MLR and BFR/SR tended to produce higher oxygen transfer efficiency. Surprisingly, the reactor-solution posed the same level of resistance as clean water in all experiments, except in a 5-day SRT, non-nitrifying, completely mixed activated sludge (CMAS) process run. Furthermore, SBFR successfully represented biological floc and showed a positive correlation to sludge volume index (SVI). In addition, SBFR/SR and oxygen transfer efficiency (OTE(f)) followed an exponential relationship for the complete data set. The method of separating the mixed-liquor into biological floc and reactor-solution improved the understanding of oxygen transfer under process conditions, without resorting to intrusive techniques or direct handling of fragile biological floc., (Copyright 2005 Wiley Periodicals, Inc.)

In this investigation, a laboratory-scale enhanced biological phosphorus removal (EBPR) process was operated under controlled conditions to study the impact of varying the influent ratio of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TP), and the consequential biochemical reactions on oxygen transfer parameters. The data showed that the experiment with high influent phosphorus relative to nitrogen (COD/TP = 51 and TKN/TP = 3.1) achieved higher alpha and oxygen transfer efficiency (OTE(f)). On the other hand, the experiment with high influent nitrogen relative to phosphorus (TKN/TP = 14.7 and COD/TP = 129) resulted in approximately 50% reduction in alpha and OTE(f) under similar organic loading. This suggested that the intracellular carbon storage and the enhanced biological P removal phenomenon associated with the phosphorus-accumulating organisms (PAOs) had a positive influence on OTE(f) in the high phosphorus experiment compared to an active population of nitrifying and denitrifying organisms in the high nitrogen experiment. The intracellular carbon storage by the glycogen-accumulating organisms also appeared to have had a positive effect on oxygen transfer efficiency, although to a lesser extent in comparison to the PAOs. It was also found that oxygen uptake rate (OUR) was not a good indicator of the measured alpha and OTE(f), because it was a combined effect of several biochemical reactions, each having a varying degree of influence. It is difficult to underestimate the crucial role of flocs in mass transfer of oxygen, because microorganisms associated with flocs carry out the biochemical reactions. It seems that the combination of influent characteristics and biochemical reactions in each experiment produced a unique biomass quality (determined by the biomass N to P ratio), ultimately affecting the mass transfer of oxygen. A theoretical explanation for the observed oxygen transfer efficiency under the process conditions is also proposed in this article.

Twelve independent batch experiments (<9h) with fresh municipal activated sludge were conducted to assess the occurrence and the mechanisms of deflocculation under a temperature shift from 30 to 45 degrees C. In each experiment, a transient reactor (2 L) was subjected to the temperature shift and a control reactor was operated at a constant temperature of 30 degrees C. The occurrence of deflocculation was demonstrated by the increase in turbidity and in the concentrations of biopolymers in the sludge supernatant from the transient reactor. The maximum levels of proteins in the supernatants ranged from 53 to 81 mg/L, for DNA from 34 to 36 mg/L, for humic compounds from 20 to 40 mg/L, and for carbohydrates from 21 to 31 mg/L. All the biopolymer concentrations in the control reactor remained below 5-10 mg/L. The release of biopolymers was accompanied by an increase in sludge supernatant conductivity (16-32% increase, up to 1.20 mS/cm), soluble chemical oxygen demand (from 129 to 440 mg/L), total suspended solids (>25 mg/L up to 128 mg/L), and a decrease in the mixed liquor volatile suspended solids (up to 11%). The temperature shift was also found to inhibit microbial metabolism by reducing the sludge biomass substrate removal capacity, as measured by oxygen-uptake rates. The temperature shift had a marginal effect causing sludge lysis (as an increase in beta-galactosidase activity) and had no significant impact on sludge viability (live/dead ratio of bacterial cells). It was concluded that sludge deflocculation under a temperature shift from 30 to 45 degrees C involves the solubilisation of extracellular polymeric substances from the flocs and likely also floc fragmentation. In addition, sludge deflocculation and the inhibition of microbial metabolism explain the poor treatment performance observed in previous continuous reactors under similar temperature shifts.

Cultivation of aerobic granular sludge for pentachlorophenol (PCP) degradation under microaerobic condition (DO concentration was controlled at 0.2-0.7 mg/L) was studied in this paper. Anaerobic granules were selected as inoculum. The changes of appearance were observed and the variations of SVI, VSS/TSS, PN/PS and the size of sludge were measured during cultivating. The capabilities for degradation of PCP, AOX and COD(Cr) were also studied. Observations on mature granules were carried out by scanning electron microscope, and the results indicated bacillus was dominant on the surface of granules while in the inner of granules both bacillus and coccus were the dominant microorganisms. K, Na, Fe, Ca, Mg, Ni, Co, Mn, Cu and Zn were detected in the granules by element analysis.

Colour discharges are gaining renewed focus in the pulp and paper industry as increasingly strict regulatory limits are placed on wastewater quality and aesthetics. In-mill process improvements, such as ECF bleaching and oxygen delignification, have decreased wastewater colour loadings. However, a survey of 12 pulp and paper mill systems found that effluent treatment using aerated stabilisation basins (ASB) leads to average increases in colour of 20-40%. In some instances, this phenomenon may even double the influent colour levels. Activated sludge systems did not produce a colour increase. The measured increases that follow ASB secondary treatment may be sufficient for a mill to fail prescribed discharge standards. A detailed field survey focusing on sections of an integrated bleached kraft mill ASB treatment system was undertaken. The average increase in colour at the final point of discharge was 45%. The major changes in colour concentration occurred in the inlet to the main treatment pond, and in polishing ponds that followed the main treatment pond. Both of these areas receive little or no aeration. No significant change was observed in the highly aerated main pond. These results, along with literature reports, suggested that redox conditions play a major role in influencing colour behaviour. To test this, two series of paired continuously stirred reactors were used to treat whole mill effluent from two ECF bleached kraft mills in parallel. The first series initially treated under anaerobic conditions, followed by an aerobic reactor, while the second series reversed this order. With the initial anaerobic stage, effluent colour increased by 18% and 19% for the first and second series respectively. Subsequent treatment by aerobic bacteria further increased colour by 14% and 6%, for a total increase of 32% and 25%. Initial aerobic treatment, however, did not lead to any significant change in colour for either effluent. Further anaerobic treatment following aerobic conditions produced only small increases in colour. These results are consistent with the ASB and activated sludge system survey, suggesting that anaerobic conditions at the head of treatment systems initiate the observed increases in effluent colour in ASB treatment systems.

The operation of an activated sludge process at a paper mill (AIPM) in Hedera, Israel, was often characterized by disturbances. As part of a research and development project, a study on new biological treatment was initiated. The study included the operation of three pilot units: a. anaerobic treatment by upflow anaerobic sludge blanket (UASB); b. aerobic treatment by two pilot units including activated sludge and membrane bioreactor (MBR), which have been operated in parallel for comparison reasons. The pilot plant working on anaerobic treatment performed COD reduction from 2,365 to 755 mg/L, expressed as average values. Based on the pilot study, a full scale anaerobic treatment system has been erected. During a period of 100 days, after achieving steady state, the MBR system provided steady operation performance, while the activated sludge produced effluent characterized by oscillatory qualities. The following results, based on average values, indicate much lower suspended solids concentrations in the MBR effluent, 2.5 mg/L, as compared to 25 mg/L in the activated sludge. The ability to develop and maintain a concentration of over 11,000 mg/L of mixed liquor volatile suspended solids in the MBR enabled an intensive bioprocess at relatively high cell residence time. This study demonstrates that the anaerobic process, followed by aerobic MBR can provide effluent of high quality which can be considered for economic reuse in the paper mill industry.

Three operating strategies were tested for decreasing activated sludge deflocculation due to temperature shifts from 30 degrees to 45 degrees C: magnesium sludge enrichment, increased sludge retention time (33 d), and spikes of an easily degradable substrate (methanol). The temperature shifts were conducted sequentially in 4 parallel lab-scale sequencing batch reactors (SBRs) treating kraft pulp mill effluent. Three SBRs operated at an SRT = 20 days, and in one of them the sludge was not manipulated, thus, serving as a reference SBR. The temperature shift was associated with decreased soluble chemical oxygen demand (SCOD) removals, decreased sludge settleability and substrate removal capacity, and increased effluent suspended solids (ESS) and turbidity levels. The shift also increased the sludge specific respiration rates and reduced the sludge substrate removal capacity. Sludge deflocculation was assessed as floc solubilisation (increased effluent SCOD levels) and floc fragmentation (increase in effluent solids smaller than 50 microm). Mg enrichment of the sludge and methanol spikes reduced the ESS levels (in 9 and 25%), and the three operating strategies decreased effluent turbidity (in 22-35%) compared to the maximum levels from the non-manipulated reactor (44 mg ESS/L). The stronger sludge floc structure achieved by magnesium enrichment and a high sludge age of 33 days was unsuccessful in significantly decreasing deflocculation. The mechanisms involved in sludge deflocculation require further fundamental research.

The effects of temperature variations on aerobic biological wastewater treatment were evaluated with respect to treatment efficiency, solids discharges, sludge physicochemical properties and microbiology. The effects of controlled temperature shifts (from 35 degrees to 45 degrees C; from 45 degrees to 35 degrees C) and periodic temperature oscillations (from 31.5 degrees C to 40 degrees C, 6-day period, for 30 days) were assessed in 4 parallel, lab-scale sequencing batch reactors (SBRs) that treated pulp and paper mill effluent. Overall, the temperature shifts caused higher effluent suspended solids (ESS) levels (25-100 mg/L) and a decrease (up to 20%) in the removal efficiencies of soluble chemical oxygen demand (SCOD). Lower ESS levels were triggered by a slow (2 degrees C/day) versus a fast (10 degrees C/12h) temperature shift from 35 degrees to 45 degrees C, but the SCOD removal efficiencies decreased similarly in both cases (from 66+/-3% and 65+/-2% to 49+/-3% and 51+/-3%). Temperature oscillations caused an increased deterioration of the sludge settleability [high sludge volume indices (SVI); low zone settling velocities (ZSV)], high ESS levels and lower SCOD removals. The temperature transients were associated with poor sludge settleability (SVI>100 mL/g MLSS, ZSV<1 cm/min), more negatively charged sludge (up to -0.35+/-0.03 meq/g MLSS), increased filament abundance (approximately 4 to 4.5, subjective scale equivalent to very common), and decreased concentrations of protozoa and metazoa (25,000-50,000 microorganisms/mL sludge). The controlled, periodic temperature oscillations had a slight impact on SCOD removal efficiency (5% decrease), and did not seem to select for robust microorganisms that withstood the temperature shift. Sludge deflocculation and filament proliferation caused by these temperature transients may explain the higher ESS levels.