Full-scale Wastewater Treatment Processes Research Articles

Combining large-scale investigation and quantum chemical calculation of pharmaceuticals: Spatiotemporal patterns of occurrence and structural insights into removal

This study investigated the spatiotemporal distribution of 17 pharmaceuticals in wastewater treatment plants (WWTPs) from 17 provinces across China, and explored structural insights into their removal in full-scale wastewater treatment processes by quantum chemistry. Briefly, 10 pharmaceuticals were detected in above 85 % of samples, of which ibuprofen and sulfamethoxazole dominated with concentrations up to the μg/L level. Seasonally, concentrations of psychoactive drugs (PDs) were 1.3–2.6 times higher in summer than in other seasons. Spatially, higher average concentrations were detected in northern WWTPs, and regions with similar economic levels exhibited similar contamination patterns. Pharmaceutical removal in WWTPs ranged from 41.4 % (carbamazepine) to 87.2 % (sulfamethizole), with the secondary treatment segment, especially aerobic treatment units, maintaining an important position. Molecular structural mechanisms behind these removal performances were further revealed. Firstly, we demonstrated a significant association of pharmaceutical overall removal with electrophilicity index (ωcubic) as well as the lowest unoccupied molecular orbital energy (ELUMO). Highly electrophilic pharmaceuticals may persist in WWTPs and their sensitivity to electron exchange reactions accounted for the discrepant removal. In terms of treatment segments, pharmaceuticals with reaction sites masked in molecular structure, such as ibuprofen and venlafaxine, showed a propensity for tertiary treatment suitability. Furthermore, enzymes of aerobic units exhibited excellent docking affinity to pharmaceutical molecules with an average affinity of −7.2 kcal/mol, and hydrogen-bond interactions played an important factor in promoting biodegradation. Our results emphasize the necessity of assessing pharmaceutical contamination on a larger spatiotemporal scale. Moreover, the structural insights into removal phenomena offer scientific molecular-level justification for the design and optimization of pharmaceutical treatment technologies in WWTPs.

Occurrence, distribution, and behaviors of erythromycin A, production byproducts, transformation products, and resistance genes in a full-scale erythromycin A production wastewater treatment system

Antibiotic production wastewater from pharmaceutical manufacturing is a significant source of antibiotic and resistance gene pollution in the environment. Given that Erythromycin A (Ery-A) is a widely used antibiotic in both human clinical and livestock breeding, it is imperative to ascertain its presence, along with related compounds, in the biological treatment processes of production wastewater. In this study, the occurrence and behavior of Ery-A, its production byproducts, transformation products, and resistance genes were first systematically investigated in a full-scale anaerobic-aerobic system for treating Ery-A production wastewater. Simultaneously, residual antibacterial activity in wastewater and sludge was evaluated throughout the wastewater treatment process. Ery-A contributes only 24.2 – 36.0% to the antibacterial activities. Ery-A-derived compounds including production byproducts (erythromycin B and erythromycin C) and transformation products (anhydro erythromycin A, N-demethyl-erythromycin A, and erythromycin A enol ether), are determined to contribute to the antibacterial activities of the wastewater treatment system. High concentrations of antibiotics with antibacterial activity (up to 1,258.9 mg/kg·TS for erythromycin A enol ether) adsorbed in the sludge result in near collapse of the first-stage anaerobic sludge system. Sludge biodegradation in second-stage anaerobic and anoxic-aerobic tanks is essential in removing Ery-A-related compounds from wastewater. The Ery-A-related compounds in the secondary effluent and excess sludge are determined to be 44.5 g/h and 1.5 g/h through the mass balance analysis, respectively. The discharge of MLS resistance genes from the secondary effluent and excess sludge is 1.0 × 1016 copies/h and 7.1 × 1015 copies/h, respectively. These findings highlight the significant concern over the release of Ery-A-related compounds and MLS resistance genes from the Ery-A production wastewater treatment system. As a result, it is crucial to implement strategies for the removal of Ery-A-related compounds from production wastewater before biological processes. This study is the first to report the occurrence and behavior of Ery-A-related compounds and resistance genes along the full-scale wastewater treatment processes. Additionally, it sheds light on the importance of byproducts and transformation products with antibacterial activity from Ery-A in the Ery-A production wastewater treatment system.

Sialylation and Sulfation of Anionic Glycoconjugates Are Common in the Extracellular Polymeric Substances of Both Aerobic and Anaerobic Granular Sludges.

Anaerobic and aerobic granular sludge processes are widely applied in wastewater treatment. In these systems, microorganisms grow in dense aggregates due to the production of extracellular polymeric substances (EPS). This study investigates the sialylation and sulfation of anionic glyconconjugates in anaerobic and aerobic granular sludges collected from full-scale wastewater treatment processes. Size exclusion chromatography revealed a wide molecular weight distribution (3.5 to >5500 kDa) of the alkaline-extracted EPS. The high-molecular weight fraction (>5500 kDa), comprising 16.9-27.4% of EPS, was dominant with glycoconjugates. Mass spectrometry analysis and quantification assays identified nonulosonic acids (NulOs, e.g., bacterial sialic acids) and sulfated groups contributing to the negative charge in all EPS fractions. NulOs were predominantly present in the high-molecular weight fraction (47.2-84.3% of all detected NulOs), while sulfated glycoconjugates were distributed across the molecular weight fractions. Microorganisms, closely related to genera found in the granular sludge communities, contained genes responsible for NulO and sulfate group synthesis or transfer. The similar distribution patterns of sialylation and sulfation of the anionic glycoconjugates in the EPS samples indicate that these two glycoconjugate modifications commonly occur in the EPS of aerobic and anaerobic granular sludges.

Microbial Roles in Dissolved Organic Matter Transformation in Full-Scale Wastewater Treatment Processes Revealed by Reactomics and Comparative Genomics.

Understanding the degradation of dissolved organic matter (DOM) is vital for optimizing DOM control. However, the microbe-mediated DOM transformation during wastewater treatment remains poorly characterized. Here, microbes and DOM along full-scale biotreatment processes were simultaneously characterized using comparative genomics and high-resolution mass spectrometry-based reactomics. Biotreatments significantly increased DOM's aromaticity and unsaturation due to the overproduced lignin and polyphenol analogs. DOM was diversified by over five times in richness, with thousands of nitrogenous and sulfur-containing compounds generated through microbe-mediated oxidoreduction, functional group transfer, and C-N and C-S bond formation. Network analysis demonstrated microbial division of labor in DOM transformation. However, their roles were determined by their functional traits rather than taxa. Specifically, network and module hubs exhibited rapid growth potentials and broad substrate affinities but were deficient in xenobiotics-metabolism-associated genes. They were mainly correlated to liable DOM consumption and its transformation to recalcitrant compounds. In contrast, connectors and peripherals were potential degraders of recalcitrant DOM but slow in growth. They showed specialized associations with fewer DOM molecules and probably fed on metabolites of hub microbes. Thus, developing technologies (e.g., carriers) to selectively enrich peripheral degraders and consequently decouple the liable and recalcitrant DOM transformation processes may advance DOM removal.

Occurrence and transformation of phosphonates in textile dyeing wastewater along full-scale combined treatment processes

Phosphonates discharged from wastewater treatment plants (WWTPs) have attracted increasing concerns because of their potential impact on eutrophication and potential risks to aquatic ecosystems. However, very few studies are available on their occurrence and transformation in WWTPs, partly due to the lack of sensitive methods for phosphonate analysis in complex matrices. Herein, based on our recent progress in phosphonate analysis, the occurrence and transformation of phosphonates along the full-scale wastewater treatment processes of two textile dyeing WWTPs were revealed. A set of typical phosphonates, including six phosphonate chelators (PCs) and four potential degradation products of PCs (DP-PCs) were quantified in different units and the final dewatered sludge. Three PCs (2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), 1-hydroxyethane 1,1-diphosphonic acid (HEDP) and nitrilotris(methylene phosphonic acid) (NTMP)) at upmost mg/L and a considerable amount of four DP-PCs (9.12–608 μg/L) were detected in the influents of both WWTPs. In the subsequent treatment, NTMP could be removed more efficiently than PBTC and HEDP, especially in the coagulation unit, and the dissolved phosphonates were eliminated more readily than other dissolved organic phosphorus fractions. Of particular note, the toxicologically critical DP-PC (i.e., aminomethylphosphonic acid) was produced during the coagulation and biological treatment units. The final precipitation unit seemed essential to ensure satisfactory removal of PCs and DP-PCs. In addition, a significant accumulation of phosphonates in dewatered sludge (up to 7.81 g/kg) and the widespread occurrence of harmful DP-PCs also reminded us to pay more concerns on their potential risks during further sludge disposal in future.

Microbial community evolution and fate of antibiotic resistance genes along six different full-scale municipal wastewater treatment processes

The evolution of microbial community and the fate of ARGs along different full-scale wastewater treatment processes (i.e., Anaerobic-Anoxic-Oxic, Oxidation Ditch, and Cyclic Activated Sludge System) were investigated in this study. We found that the sludges of bioreactors treating similar influent showed the similar microbial communities, independent of the treatment technologies. The horizontal gene transfer (HGT) mainly occurred in aeration tank rather that anaerobic/anoxic tank. More co-occurrence of potential pathogens and ARGs was found in wastewater than in sludge. Microbial biomass was the key driver for the fate of ARGs in wastewater, while mobile genetic elements (MGEs) was the key factor for the fate of ARGs in sludge. Combination of wastewater characteristics, microbial diversity, microbial biomass, and MGEs contributed to the variation of ARGs. Finally, it was found that enhanced nutrients removal process and tertiary treatment would benefit ARGs removal.

Evaluation of Diagnosis-based Control Strategy for NH<sub>4</sub>-N and NOX-N Removal of a Full-scale Wastewater Treatment Process

Evaluation of Diagnosis-based Control Strategy for NH<sub>4</sub>-N and NOX-N Removal of a Full-scale Wastewater Treatment Process

Fate of cefotaxime-resistant Enterobacteriaceae and ESBL-producers over a full-scale wastewater treatment process with UV disinfection

Disinfection by UV radiation is one of the most promising solutions to reduce the bacterial load and antibiotic resistance in the final effluents of urban wastewater treatment plants (UWTP). Our aim was to evaluate the fate of cefotaxime-resistant Enterobacteriaceae and Extended Spectrum Beta-Lactamase (ESBL) producers in a full-scale system that includes UV-C disinfection. Over treatment, the abundance of cefotaxime-resistant Enterobacteriaceae was reduced, with reductions of 1.9 log units after secondary treatment (STW samples) and 1.8 log following UV disinfection (UTW samples). These reductions, did not reflect the variations in the prevalence of cefotaxime-resistant Enterobacteriaceae, estimated to be of 3% in raw wastewater (RW), 18% in STW and 3% in UTW. A significant increase of cefotaxime-resistant bacterial counts (0.5 log; p < 0.05) was observed after 3 days of storage. In a total of 1799 cefotaxime-resistant Enterobacteriaceae isolates, 15% harboured blaCTX-M (n = 274), 11% blaTEM (n = 194) and 4% blaSHV (n = 72). While the ESBL gene prevalence decreased over treatment, the prevalence of the intI1 gene decreased after ST but slightly increased in UTW samples. The blaCTX-M-carriers were identified as Escherichia coli and Klebsiella pneumoniae, mostly multi-drug resistant (90.5%) and carrying integrase genes (82.8%). The blaCTX-M gene variants (48 blaCTX-M-15, 9 blaCTX-M-32, 8 blaCTX-M-1, 5 blaCTX-M-27, and 2 blaCTX-M-14) were flanked by ISEcp1, ISEcp1/IS26, IS903 and ORF477 in 8 different arrangements. The IncF plasmid replicon type was highly prevalent among blaCTX-M-carrying Escherichia coli (74.5%) while IncR predominated among K. pneumoniae (54.5%).Our results confirmed the potential of UV-C disinfection to remove antibiotic resistant bacteria. Still, resistant Enterobacteriaceae (about 30 × 106 cells per m3 of water), presenting traits that might potentiate antibiotic resistance spread, are released in the final effluent. In addition, a significant regrowth was observed after storage. These results suggest that improvements of wastewater disinfection are still required to minimize the risks associated with UWTP discharges.

Characteristics of greenhouse gas emission in three full-scale wastewater treatment processes

Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic (reversed A2O) and anaerobic/anoxic/aerobic (A2O), were selected to investigate the emission characteristics of greenhouse gases (GHG), including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Results showed that although the processes were different, the units presenting high GHG emission fluxes were remarkably similar, namely the highest CO2 and N2O emission fluxes occurred in the aerobic areas, and the highest CH4 emission fluxes occurred in the grit tanks. The GHG emission amount of each unit can be calculated from its area and GHG emission flux. The calculation results revealed that the maximum emission amounts of CO2, CH4 and N2O in the three wastewater treatment processes appeared in the aerobic areas in all cases. Theoretically, CH4 should be produced in anaerobic conditions, rather than aerobic conditions. However, results in this study showed that the CH4 emission fluxes in the forepart of the aerobic area were distinctly higher than in the anaerobic area. The situation for N2O was similar to that of CH4: the N2O emission flux in the aerobic area was also higher than that in the anoxic area. Through analysis of the GHG mass balance, it was found that the flow of dissolved GHG in the wastewater treatment processes and aerators may be the main reason for this phenomenon. Based on the monitoring and calculation results, GHG emission factors for the three wastewater treatment processes were determined. The A2O process had the highest CO2 emission factor of 319.3 g CO2/kg CODremoved, and the highest CH4 and N2O emission factors of 3.3 g CH4/kg CODremoved and 3.6 g N2O/kg TNremoved were observed in the Orbal oxidation ditch process.

Energy saving membrane treatment of high organic load industrial effluents: From lab to pilot scale

In this study, a nanofiltration unit was implemented at an industrial site, for the treatment of industrial wastewater generated during rubber tubing extrusion. The aim was to reduce the energy input required, while assuring a final effluent quality that meets the requirements of environmental legislation. In a first stage, two membrane process treatments, ultrafiltration and nanofiltration, were evaluated at laboratory scale in order to assess the rejection of pollutants and maximise permeate throughput. Permeate generated from nanofiltration using either an NF90 or an NF270 membrane were shown to meet the effluent discharge requirements (<2000 mg COD/l). The less restrictive membrane, NF270, was chosen for study in a pilot plant at the industrial site, due to its higher membrane permeability. The pilot nanofiltration unit was integrated into the treatment plant operation aiming at optimising the process in terms of the efficiency of pollutant removal with minimal energy input. A feasibility study was performed for this case-study and it was concluded that the energy expenditure of the new process represents only 62% of the current energy consumption of the treatment plant. The proposed solution in this work may be retrofitted to full scale wastewater treatment processes, and may be applicable to industries that employ similar manufacturing processes, and face similar difficulties.

Biodegradation in a soil environment of activated sludge derived polyhydroxyalkanoate (PHBV)

Mixed culture (activated sludge) polyhydroxyalkanoates (PHAs) produced in conjunction with wastewater treatment and compounded into bioplastics have applications in agriculture. Rates of biodegradation and any influence of degradation products need to be characterised in-situ in soil environments for applications involving PHA-based product degradation (either as a controlled intent in product service or a criterion for product end-of-life management). We performed such characterisation as part of the initial stages of product development of native copolymers of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV). This PHBV was accumulated in and recovered from activated sludge produced in pilot and full-scale wastewater treatment processes. The rates of PHBV biodegradation in soil were quantified using a broad range of HV content material (12 mol %–72 mol %) and referenced to a cellulose control. For mixed culture PHBVs, 90% biodegradation was expected to occur between 10.7 and 22.2 months. Germination studies using a standard cress seed assay indicated that PHA biodegradation products had no influence on germination activity in soil. Soil extracts examined during polymer degradation were non-toxic (Microtox).Mechanisms of biodegradation were examined by means of physico-chemical characterisation and Atomic Force Microscopy (AFM). Biodegradation occurred at the polymer surface and the rate was governed by both biodeterioration and depolymerisation, which were shown to be controlled by a combination of copolymer composition, crystallinity, microstructure and surface morphology.

Bacterial phosphate metabolism and its application to phosphorus recovery and industrial bioprocesses

Enhanced biological phosphorus removal (EBPR) has become a well-established process and is currently applied in many full-scale wastewater treatment processes. Phosphorus recovered from EBPR waste sludge can be used as a raw material for the fertilizer industry, if a sound recycling strategy is developed and applied. In this review, we summarize our current knowledge on phosphate metabolism in bacteria, focusing on molecular mechanisms of bacterial polyphosphate (polyP) accumulation. A simple method for releasing polyP from EBPR waste sludge and recovering phosphorus in a reusable form for the fertilizer industry is presented. We also describe a recent development of bioprocesses for the expanded use of polyP in the production of value-added chemicals.

Hybrid Fuzzy Modeling of Wastewater Quality with Artificial Intelligence Learning

The wastewater treatment process (WWTP) is highly nonlinear and complex, and its dynamics are difficult to model. Process data obtained under multiple operating conditions that have a number of operating models and changes in operating conditions, such as biological WWTP, should be modeled carefully. In this paper, we propose a new hybrid technique for modeling wastewater quality that is based on the Takagi-Sugeno-Kang fuzzy model with artificial intelligence learning and employs real-coded genetic algorithms. The hybrid learning framework integrates the multiple fuzzy model, which can find the rule base and the membership functions of the fuzzy model simultaneously. We applied the proposed method to predict the effluent chemical oxygen demand in a full-scale coke wastewater treatment plant. The modeling results show that the hybrid model can accurately model the real nonlinear processes under diverse operating conditions, and that it is able to identify various operating regions in a full-scale WWTP.

Abundance and ecophysiology of Defluviicoccus spp., glycogen-accumulating organisms in full-scale wastewater treatment processes

The activity of glycogen-accumulating organisms (GAOs) in enhanced biological phosphorus removal (EBPR) wastewater treatment plants has been proposed as one cause of deterioration of EBPR. Putative GAOs from the Alphaproteobacteria, Defluviicoccus spp. (including D. vanus), were studied in full-scale EBPR plants to determine their distribution, abundance and ecophysiology. Fluorescence in situ hybridization (FISH) demonstrated that Defluviicoccus spp. were generally low in abundance; however, in one plant surveyed, Cluster 2 Defluviicoccus constituted 9 % of all Bacteria. FISH combined with microautoradiography revealed that both Cluster 1 and Cluster 2 Defluviicoccus were capable of taking up a narrow range of substrates including acetate, propionate, pyruvate and glucose under anaerobic and aerobic conditions. Formate, butyrate, ethanol and several other substrates were not taken up. Cluster 2 Defluviicoccus demonstrated a phenotype consistent with the current metabolic model for GAOs--anaerobic assimilation of acetate and reduction to polyhydroxyalkanoates (PHA) using the glycolytic pathway, and aerobic consumption of PHA. Polyphosphate-accumulating organisms (PAOs, 'Candidatus Accumulibacter phosphatis') and other putative GAOs ('Candidatus Competibacter phosphatis') co-existed in two plants with Cluster 2 Defluviicoccus, but in both plants, the latter organisms were more abundant. Thus Cluster 2 Defluviicoccus can be relatively abundant and could be carbon competitors of PAOs and other GAOs in EBPR plants.

Application of fuzzy partial least squares (FPLS) modeling nonlinear biological processes

We applied a nonlinear fuzzy partial least squares (FPLS) algorithm for modeling a biological wastewater treatment plant. FPLS embeds the Takagi-Sugeno-Kang (TSK) fuzzy model into the regression framework of the partial least squares (PLS) method, in which FPLS utilizes a TSK fuzzy model for nonlinear characteristics of the PLS inner regression. Using this approach, the interpretability of the TSK fuzzy model overcomes some of the handicaps of previous nonlinear PLS (NLPLS) algorithms. As a result, the FPLS model gives a more favorable modeling environment in which the knowledge of experts can be easily applied. Results from applications show that FPLS has the ability to model the nonlinear process and multiple operating conditions and is able to identify various operating regions in a simulation benchmark of biological process as well as in a full-scale wastewater treatment process. The result shows that it has the ability to model the nonlinear process and handle multiple operating conditions and is able to predict the key components of nonlinear biological processes.

A comprehensive insight into floc characteristics and their impact on compressibility and settleability of activated sludge

This paper presents a comprehensive study of sludge floc characteristics and their impact on compressibility and settleability of activated sludge in full scale wastewater treatment processes. The sludge flocs were characterised by morphological (floc size distribution, fractal dimension, filament index), physical (flocculating ability, viscosity, hydrophobicity and surface charge) and chemical (polymeric constituents and metal content) parameters. Compressibility and settleability were defined in terms of the sludge volume index (SVI) and zone settling velocity (ZSV). The floc morphological and physical properties had important influence on the sludge compressibility and settleability. Sludges containing large flocs and high quantities of filaments, corresponding to lower values of fractal dimension ( D f), demonstrated poor compressibility and settleability. Sludge flocs with high flocculating ability had lower SVI and higher ZSV, whereas high values of hydrophobicity, negative surface charge and viscosity of the sludge flocs correlated to high SVI and low ZSV. The quantity of the polymeric compounds protein, humic substances and carbohydrate in the sludge and the extracted extracellular polymeric substances (EPS) had significant positive correlations with SVI. The ZSV was quantitatively independent of the polymeric constituents. High concentrations of the extracted EPS were related to poor compressibility and settleability. The cationic ions Ca, Mg, Al and Fe in the sludge improved significantly the sludge compressibility and settleability.

Glycogen-accumulating organisms in laboratory-scale and full-scale wastewater treatment processes.

Laboratory-scale sequencing batch reactors (SBRs) as models for wastewater treatment processes were used to identify glycogen-accumulating organisms (GAOs), which are thought to be responsible for the deterioration of enhanced biological phosphorus removal (EBPR). The SBRs (called Q and T), operated under alternating anaerobic-aerobic conditions typical for EBPR, generated mixed microbial communities (sludges) demonstrating the GAO phenotype. Intracellular glycogen and poly-beta-hydroxyalkanoate (PHA) transformations typical of efficient EBPR occurred but polyphosphate was not bioaccumulated and the sludges contained 1.8% P (sludge Q) and 1.5% P (sludge T). 16S rDNA clone libraries were prepared from DNA extracted from the Q and T sludges. Clone inserts were grouped into operational taxonomic units (OTUs) by restriction fragment length polymorphism banding profiles. OTU representatives were sequenced and phylogenetically analysed. The Q sludge library comprised four OTUs and all six determined sequences were 99.7% identical, forming a cluster in the gamma-Proteobacteria radiation. The T sludge library comprised eight OTUs and the majority of clones were Acidobacteria subphylum 4 (49% of the library) and candidate phylum OP10 (39% of the library). One OTU (two clones, of which one was sequenced) was in the gamma-Proteobacteria radiation with 95% sequence identity to the Q sludge clones. Oligonucleotide probes (called GAOQ431 and GAOQ989) were designed from the gamma-Proteobacteria clone sequences for use in fluorescence in situ hybridization (FISH); 92% of the Q sludge bacteria and 28% of the T sludge bacteria bound these probes in FISH. FISH and post-FISH chemical staining for PHA were used to determine that bacteria from a novel gamma-Proteobacteria cluster were phenotypically GAOs in one laboratory-scale SBR and two full-scale wastewater treatment plants. It is suggested that the GAOs from the novel cluster in the gamma-Proteobacteria radiation be named 'Candidatus Competibacter phosphatis'.

Adaptive modeling and classification of the secondary settling tank

In biological wastewater treatment plants the biomass is separated from the treated wastewater in the secondary settler; thus, efficient operation of the secondary settler is crucial to achieving satisfactory effluent quality in the wastewater treatment process (WWTP). In the present work, system identification and soft-computing techniques were used to formulate a model for predicting the solid volume index (SVI) and classification of the sludge bulking phenomenon in the settler. An adaptive time series model was applied to predict the SVI of the secondary settler; this model uses the recursive least square (RLS) method to update the model parameters. The method for classifying the current state of the secondary settler is based on the strong correlation that was observed between the settler state and the values of the time series model parameters, which enabled the time series model parameters to be used as effective features for monitoring the secondary settler. To classify the current state of the secondary settler, a neural network (NN) was used to classify the adaptive time series model parameters, where a hybrid Genetic Algorithm (GA) was used to decide the number of hidden nodes of the NN classifier. Application of the proposed method to a full-scale WWTP demonstrated the utility of the method for simultaneously predicting the SVI value of the secondary settler and classifying the current state of the settler.

PHOSPHATE UPTAKE KINETICS IN RELATION TO PHB UNDER AEROBIC CONDITIONS

A characteristic of the biological phosphorus removal process is the interaction between different intracellular components. Therefore, an understanding of the effects of the intracellular components on biological phosphorus removal is essential for the practical application of the process. In this study, the stoichiometry of poly-hydroxybutyrate (PHB) to P-uptake and the kinetics of uptake of ortho-phosphate in relation to PHB were investigated under aerobic and substrate limiting conditions in batch experiments with activated sludge from a biological phosphorus removal process. The stoichiometry of PHB to P-uptake was investigated by determination of the degradation rate of PHB under aerobic conditions in the presence and absence of ortho-phosphate in the bulk liquid. The degradation of PHB as a function of time was described by a first-order equation. The presence of ortho-phosphate increased the rate of PHB degradation significantly, confirming that the uptake of ortho-phosphate directly required PHB. The fraction of PHB used for uptake of ortho-phosphate from the bulk liquid was estimated to be 30%. Furthermore, batch experiments confirmed that the uptake rate of ortho-phosphate under aerobic conditions was highly dependent on the concentration of PHB in the biomass. The observed uptake rate of ortho-phosphate as a function of the PHB concentration was mathematically described by a Monod equation. The maximum uptake rate of the sludge was estimated to be 14 (mg-P/g-VSS)/h. The obtained results add to the understanding of the mechanisms of the biological phosphorus removal process under the stress conditions with limiting substrate supplies present in the full-scale wastewater treatment process. Furthermore, the results indicate that control strategies to stabilise the process should focus on a maintenance and optimal utilisation of PHB. © 1998 Elsevier Science Ltd. All rights reserved

Molecular Weight Distributions of Soluble Organic Matter in Various Secondary and Tertiary Effluents

Differences in the nature of soluble organic matter were measured for various full-scale wastewater treatment processes. Conventional activated sludge, pure oxygen activated sludge, biofiltration, granular activated carbon, and tertiary sand filtration were evaluated. Effluent soluble organic matter was analyzed by ultrafiltration for the apparent molecular weight distribution of soluble organic carbon and UV-absorbing material. The effects of annual season, secondary treatment process, and tertiary treatment process upon the properties of the effluent soluble organic matter were statistically significant at the 99% level. Effluent properties from the various treatments were sufficiently different to support the concept of the selection of appropriate treatments to minimize the effluent concentration of specific fractions of the soluble organic material as required for specific water reuse applications.