Influent Wastewater Characteristics Research Articles

Mechanistic investigation of azo dye removal from carbon-deficient dyeing wastewater using horizontal-vertical constructed wetlands

Azo dye degradation can be achieved by simulating a series of anaerobic and aerobic conditions within the constructed wetland (CW) system. The current investigation evaluated the effectiveness of a baffled horizontal-vertical CW system, planted with Typha angustifolia, simulating anaerobic-aerobic conditions to treat carbon-deficient synthetic dyeing wastewater containing 100 mg/L Reactive Yellow 145 (RY145) azo dye. In the absence of an available carbon source in dyeing wastewater, an optimum quantity of sodium acetate was supplemented as the substrate for microbial degradation of RY145. Influent dyeing wastewater characteristics were 5555 ADMI colour, 461 mg/L chemical oxygen demand (COD) and 39 mg/L total nitrogen (TN). During the operation period, the CW system achieved 97% colour, 87% COD, 95% ammonium nitrogen (NH4+-N) and 71% TN removals at 4 d hydraulic retention time (HRT). Favourable environmental conditions, such as low redox conditions and substrate availability in horizontal CW, contributed to a significant reduction in colour (96%). Most TN reduction (67%) happened in horizontal CW by denitrification and plant assimilation. The metagenomic study revealed that Proteobacteria, Bacteroidetes, Chloroflexi and Firmicutes were responsible for pollutant degradation within horizontal CW. The UV–visible spectra and high-resolution liquid chromatograph mass spectrometer (HR-LCMS) analysis confirmed that dye degradation intermediates generated from the breakage of azo bonds were eliminated in vertical CW with high redox conditions. The results of the phytotoxicity and fish toxicity experiments demonstrated a substantial toxicity reduction in the CW system-treated effluent.

Performance analysis of three pilot-scale multi-compartment anaerobic baffled reactors treating domestic wastewater at psychrophilic temperatures in Colorado.

A transition from inefficient aerobic wastewater treatment methods to sustainable approaches is needed. Anaerobic bioreactors are a viable solution as they consume less energy, reduce biosolid production, and provide a source of renewable methane-rich biogas. A barrier to widespread implementation of anaerobic technologies is the lack of design guidance, especially in colder climates. This study bridges this knowledge gap by deriving design principles from three long-running pilot-scale anaerobic baffled reactors (ABRs) operating under psychrophilic conditions. The ABRs removed an average of 56% and 80% chemical oxygen demand (COD) and suspended solids, respectively, with a methane yield of 0.21L CH4 /g CODrem . Methane production may be improved with increased influent sCOD concentrations and decreased sulfate concentrations. Results suggest that ABRs can treat a range of wastewater strengths accompanied by useable methane production. Despite sharing location, temperature, and HRT, the ABRs displayed distinct performances, highlighting the significance of influent wastewater characteristics. PRACTITIONER POINTS: ABRs achieved 56% and 80% removal efficiencies for COD and suspended solids. Average biogas was 63% methane, and methane yield was 0.21 L CH4 /g CODrem . Volumetric methane production was positively correlated with the influent sCOD/sulfate ratio and negatively correlated with influent sulfate loading.

Factors Influencing Gaseous Emissions in Constructed Wetlands: A Meta-Analysis and Systematic Review.

Constructed wetlands (CWs) are an eco-technology for wastewater treatment and are applied worldwide. Due to the regular influx of pollutants, CWs can release considerable quantities of greenhouse gases (GHGs), ammonia (NH3), and other atmospheric pollutants, such as volatile organic compounds (VOCs) and hydrogen sulfide (H2S), etc., which will aggravate global warming, degrade air quality and even threaten human health. However, there is a lack of systematic understanding of factors affecting the emission of these gases in CWs. In this study, we applied meta-analysis to quantitatively review the main influencing factors of GHG emission from CWs; meanwhile, the emissions of NH3, VOCs, and H2S were qualitatively assessed. Meta-analysis indicates that horizontal subsurface flow (HSSF) CWs emit less CH4 and N2O than free water surface flow (FWS) CWs. The addition of biochar can mitigate N2O emission compared to gravel-based CWs but has the risk of increasing CH4 emission. Polyculture CWs stimulate CH4 emission but pose no influence on N2O emission compared to monoculture CWs. The influent wastewater characteristics (e.g., C/N ratio, salinity) and environmental conditions (e.g., temperature) can also impact GHG emission. The NH3 volatilization from CWs is positively related to the influent nitrogen concentration and pH value. High plant species richness tends to reduce NH3 volatilization and plant composition showed greater effects than species richness. Though VOCs and H2S emissions from CWs do not always occur, it should be a concern when using CWs to treat wastewater containing hydrocarbon and acid. This study provides solid references for simultaneously achieving pollutant removal and reducing gaseous emission from CWs, which avoids the transformation of water pollution into air contamination.

Application of Palm Kernel Shell Granular Filter Medium for Decolourisation and COD Removal from Clarified Palm Oil Mill Effluent

Palm oil mill effluent (POME) is characterised by high colour, COD and solids. Extraction and drying of the suspended solids for reuse as solid fuel shows great promise. However, the clarified wastewater may require further treatment to meet discharge limits. This study was aimed at evaluating the efficiency and kinetics of COD and colour removal from clarified POME using palm kernel shell (PKS) granular filter media and a sand filter as reference. The wastewater was collected from a small-scale palm oil processing mill in the Abura Aseibu Kwamankese District of Ghana and clarified using a solid-liquid separation system. The filter media of particle size 1.18mm was packed into acrylic cylinders (6cm dia.) to a height of 35.4 cm. The characteristics of influent wastewater and filter media were determined prior to the experiment following standard methods. Each filter was run as a batch system under anaerobic conditions by maintaining a minimum supernatant height of 10cm. Effluents were drawn from the bottom of each filter after 0, 24, 48, 72, 96, and 120 h for analysis using standard analytical methods. The removal efficiencies for the PKS and sand filters were, respectively, 77% and 79% for COD and 69% and 62% for colour. The COD removal was consistent with first-order kinetics for both PKS and sand filters. However, colour removal in PKS and sand filters followed second- and zero-order kinetics respectively. The correlation coefficients of the selected kinetic models show a strong correlation between the experimental and predicted results. Further research is required to establish the retention time required to bring the pollutant levels below the allowable limits for discharge into the environment.

BioWin® modeling of anaerobic sludge blanket treatment of domestic wastewater

Anaerobic bioreactors treating wastewater have lower operating costs and waste sludge generation and produce more energy-rich methane than traditional aerobic systems. The ability to simulate performance of anaerobic mainstream treatment allows for comparison to the existing aerobic treatment paradigm. Required modifications were determined for a computer simulation tool, BioWin, to predict wastewater treatment performance of a multi-compartment anaerobic baffled reactor system. The model was calibrated using one month of data and validated using two years of data pooled into three temperature regimes. The validation results were within 10 % of actual, measured values recorded from a multi-year study of a pilot-scale anaerobic bioreactor treating domestic wastewater. Sensitivity analysis showed the simulation was most sensitive to changes to the influent wastewater characteristics and acetogen and methanogen kinetic parameters. Thus, using BioWin, anaerobic domestic wastewater treatment can be integrated into wastewater facility design scenarios.

Long-term phosphorus sorption and leaching in sand filters for onsite treatment systems

The sorption capacities of sand filters used for onsite wastewater treatment and their associated risks of phosphorus (P) leaching on contact with rainwater were investigated in column experiments and with modelling tool for over 300 days. Columns packed with sand were exposed to real domestic wastewater of different characteristics and hydraulic loading modes. The wastewater fed into the columns was effluent collected from three different treatment units in the field: a septic tank (ST), biofiltration tank (BF) and Polonite® filter bag (PO). The risk of P leaching to groundwater and surface water was also assessed, by exposing the same sand columns to natural rainwater. Overall results indicated that sand soils can exhibit different adsorption and desorption capacities for electrical conductivity (EC), Total-P, phosphate-P and total suspended solids, depending on the characteristics of influent wastewater, loading rate and total operation time. The removal efficiencies of the sand columns increased in the order ST (98.16%) > PO (93.36%) > BF (81.57%) for PO4-P and slightly decreased ST (97.11%) > PO (92.06%) > BF (76.76%) for Total-P columns. All sand columns loaded with actual wastewater solutions from septic tanks and biofiltration tank have demonstrated high risks of phosphorus leaching (>99.99%) to the groundwater. The modelling was successful captured behavior of EC tracer and adsorption of PO4-P with acceptable prediction uncertainty in the PO < 8% columns. The modelling results indicated that the decrease of loading rate from 83.3 mL d-1 to 20.83 mL d-1 led to an average increase of removal efficiency and prolong operational lifetime and mass of adsorbed Total-P in the sand soil. This study concludes that sand is a valuable filter medium at low loading rate for phosphorus removal in full-scale operations of onsite treatment systems, however very vulnerable for leaching P when in contact with rainwater.

Estimation of N2O emissions from wastewater characteristics in constructed wetlands

Conventional wastewater treatment plants (WWTPs) contribute significantly to the nitrous oxide (N2O) emissions. On the other hand, the contribution of constructed wetlands (CWs) to N2O emissions is not clear. In this study, a literature review was initially conducted to study the factors that are correlated with N2O emissions from these systems. Afterwards, a statistical formula was developed using the metaregression method for estimating N2O emission factors (EFs) from CWs. This formula related EFs with influent wastewater characteristics (chemical oxygen demand-COD, total nitrogen-TN, COD/TN) and was applied to 56 small Greek settlements for predicting N2O emissions in an alternate scenario where CWs technology would be applied instead of conventional WWTPs. The estimated N2O EFs for the alternate scenario at these settlements ranged between 0.21% and 3.20% (as N2O/TN influent load), while the average value was equal to 0.94%. The specific N2O emission was estimated to 60.82 mg N2O per day and person equivalent. The application of different scenarios with wastewater of different strength showed that the lowest N2O EF in CWs is expected for wastewater with high initial COD and TN concentrations. To compare N2O emissions from CWs and conventional WWTPs, the Ordinary Least Squares multiple regression method was also applied to develop a general statistical equation that relates N2O EFs from conventional WWTPs with wastewater characteristics. According to the results, the estimated N2O emissions from the Greek settlements for conventional wastewater treatment are larger for 77% of the studied cases compared to the emissions found if CW technology had been applied instead.

Comprehensive evaluation of the carbon footprint components of wastewater treatment plants located in the Baltic Sea region

Finland and Poland share similar environmental interests with regard to their wastewater effluents eventually being discharged to the Baltic Sea. However, differences in the influent wastewater characteristics, treatment processes, operational conditions, and carbon intensities of energy mixes in both countries make these two countries interesting for carbon footprint (CF) comparison. This study aimed at proposing a functional unit (FU) which enables a comprehensive comparison of wastewater treatment plants (WWTPs) in terms of their CF. Direct emissions had the highest contribution (70%) to the total CF. Energy consumption dominated the total indirect emissions in both countries by over 30%. Polish WWTPs benefitted more from energy self-sufficiency than Finnish plants as a result of higher electricity emission factors in Poland. The main difference between indirect emissions of both countries were attributed to higher chemical consumption of the Finnish WWTPs. Total pollution equivalent removed (TPErem) FU proposed enabled a better comparison of WWTPs located in different countries in terms of their total CF. High correlations of TPErem with other FUs were found since TPErem could balance out the differences in the removal efficiencies of various pollutants. Offsetting CF was found a proper strategy for the studied WWTPs to move towards low-carbon operation. The studied WWTPs could reduce their CF from up to 27% by different practices, such as selling biofuel, electricity and fertilizers. These findings are applicable widely since the selected WWTPs represent the typical treatment solutions in Poland, Finland and in the Baltic Sea region.

Effects of influent composition on biological activity, acclimation time and microbial community profile of activated sludge

Background: The performance and stability of activated sludge (AS) processes are strongly related to influent wastewater characteristics. Objective: To investigate the influence of different chemical compositions of influent wastewater, in terms of source of carbon, on activated sludge. Methods: Response was measured in oxygen uptake rate (OUR), volatile suspended solids in the mixed liquor (MVLSS), chemical oxygen demand (COD), and microbial community profile, obtained using Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Results: Results showed that the microbial community profile obtained in both reactors is consistent with those reported for full-scale AS bioreactors treating sewage. However, when the source of carbon is less bioavailable (bioreactor 1), there was a statistically significant difference (p-value&lt;0.05, 95% confidence) in the biological activity of the biomass, both in terms of MLVSS growth and OUR in comparison with the reactor with source of carbon more bioavailable (bioreactor 2). This difference also impacted the time required for complete acclimation: it could be considered completed in 15 days in bioreactor 2, whereas in bioreactor 1, acclimation required more than 120 days to be completed, as during this period there was no net biomass growth even though there was high COD removal.

Diversity and functional prediction of microbial communities involved in the first aerobic bioreactor of coking wastewater treatment system.

The pre-aerobic process of coking wastewater treatment has strong capacity of decarbonization and detoxification, which contribute to the subsequent dinitrogen of non-carbon source/heterotrophic denitrification. The COD removal rate can reach > 90% in the first aerobic bioreactor of the novel O/H/O coking wastewater treatment system during long-term operation. The physico-chemical characteristics of influent and effluent coking wastewater in the first aerobic bioreactor were analyzed to examine how they correlated with bacterial communities. The diversity of the activated sludge microbial community was investigated using a culture-independent molecular approach. The microbial community functional profiling and detailed pathways were predicted from the 16S rRNA gene-sequencing data by the PICRUSt software and the KEGG database. High-throughput MiSeq sequencing results revealed a distinct microbial composition in the activated sludge of the first aerobic bioreactor of the O/H/O system. Proteobacteria, Bacteroidetes, and Chlorobi were the decarbonization and detoxification dominant phyla with the relative abundance of 84.07 ± 5.45, 10.89 ± 6.31, and 2.96 ± 1.12%, respectively. Thiobacillus, Rhodoplanes, Lysobacter, and Leucobacter were the potential major genera involved in the crucial functional pathways related to the degradation of phenols, cyanide, benzoate, and naphthalene. These results indicated that the comprehensive understanding of the structure and function diversity of the microbial community in the bioreactor will be conducive to the optimal coking wastewater treatment.

A coupled RTD and mixed-order kinetic model to predict high rate algal pond wastewater treatment under different operational conditions: Performance assessment and sizing application

A coupled residence time distribution (RTD) and mixed-order model was developed to simulate the performance of a pilot high rate algal pond (HRAP) for wastewater treatment under different operational conditions requiring simple influent and effluent wastewater characteristics as input data. The model showed potential in general assessment of the HRAP system performance, successfully capturing the magnitude as well as general trend of COD, TKN, TN and TP concentrations with acceptable accuracy (Nash-Sutcliffe Efficiency (NSE) value up to 0.99). However, due to the common limitation of black box model type, the detailed agreement between model and experimental data was highly varied, sometime unsatisfactory performance (NSE < 0) was obtained, especially for highly complex processes like TKN or TN removal. Besides, general information on the dynamics of algal bacterial processes under different operational conditions could be revealed by analyzing calibrated reaction order n and reaction rate constant kn values with higher n value corresponding to higher complexity of the process and higher kn values associating with higher removal rate. Moreover, the model could also be used as a quick and convenient support for HRAP design and construction by providing estimated hydraulic retention time (HRT) values required for single HRAP system treating wastewater in different case studies. Further validation with outdoor HRAP system is necessary to increase the accuracy of the model prediction.

Occurrence and Removal of Veterinary Antibiotics in Livestock Wastewater Treatment Plants, South Korea

In this study, livestock wastewater treatment plants in South Korea were monitored to determine the characteristics of influent and effluent wastewater, containing four types of veterinary antibiotics (sulfamethazine, sulfathiazole, chlortetracycline, oxytetracycline), and the removal efficiencies of different treatment processes. Chlortetracycline had the highest average influent concentration (483.7 μg/L), followed by sulfamethazine (251.2 μg/L), sulfathiazole (230.8 μg/L) and oxytetracycline (25.7 μg/L), at five livestock wastewater treatment plants. Sulfathiazole had the highest average effluent concentration (28.2 μg/L), followed by sulfamethazine (20.8 μg/L) and chlortetracycline (11.5 μg/L), while no oxytetracycline was detected. For veterinary antibiotics in the wastewater, a removal efficiency of at least 90% was observed with five types of treatment processes, including a bio-ceramic sequencing batch reactor, liquid-phase flotation, membrane bioreactor, bioreactor plus ultrafiltration (BIOSUF) and bio best bacillus systems. Moreover, this study evaluated the removal efficiency via laboratory-scale experiments on the conventional contaminants, such as organic matter, nitrogen, phosphorus and veterinary antibiotics. This was done using the hydraulic retention time (HRT), under three temporal conditions (14 h, 18 h, 27 h), using the anaerobic–anoxic–oxic (A2O) process, in an attempt to assess the combined livestock wastewater treatment process where the livestock wastewater is treated until certain levels of water quality are achieved, and then the effluent is discharged to nearby sewage treatment plants for further treatment. The removal efficiencies of veterinary antibiotics, especially oxytetracycline and chlortetracycline, were 86.5–88.8% and 87.9–90.8%, respectively, exhibiting no significant differences under various HRT conditions. The removal efficiency of sulfamethazine was at least 20% higher at HRT = 27 h than at HRT = 14 h, indicating that sulfamethazine was efficiently removed in the A2O process with increased HRT. This study is expected to promote a comprehensive understanding of the behavior and removal of veterinary antibiotics in the livestock wastewater treatment plants of South Korea.

Modeling of a full-scale sewage treatment plant to predict the nutrient removal efficiency using a long short-term memory (LSTM) neural network

A long short-term memory (LSTM)-based neural network was proposed and developed to predict the ammonium (NH4-N), total nitrogen (TN), and total phosphorus (TP) removal efficiency of an anaerobic-anoxic-oxic membrane bioreactor (A-A-O MBR) system after data visualization using Python programming. The influent wastewater characteristics, including, total organic contents, NH4-N, TN, TP, chemical oxygen demand, suspended solids, and operating parameters, such as dissolved oxygen, oxidation-reduction potential, and mixed-liquor suspended solids, were considered as inputs, while removal efficiency was taken as an output parameter. First, data analysis and its normalization were conducted to improve the learning speed of the model. Performance criteria of the proposed model were evaluated based on statistical values, including the mean-square error (MSE) and root-mean-square error-observations standard deviation ratio (RSR). Based on the goodness-of-fit values, the proposed LSTM model achieved good performance in the testing dataset; calculation results deviated little, indicated by the MSE values of 0.0047, 0.015, and 0.018 for NH4-N, TN, and TP, and RSR values of 0.0104, 0.129, and 0.141, respectively. The proposed LSTM model predicted the most precise removal efficiency for NH4-N of A-A-O MBR system, while TN and TP predictions were comparatively less accurate, but still acceptable. The proposed LSTM model is promising for predicting the nutrient removal efficiency of the A-A-O MBR system in real-time and can aid in establishing process control strategies. Therefore, the proposed LSTM model is an adequate interpolation tool to predict the nutrient removal efficiency of the A-A-O MBR process in wastewater treatment systems.

Side-stream enhanced biological phosphorus removal (S2EBPR) process improves system performance - A full-scale comparative study

To address the common challenges in enhanced biological phosphorus removal (EBPR) related to stability and unfavorable influent carbon to phosphorus ratio, a side-stream EBPR (S2EBPR) process that involves a side-stream anaerobic biological sludge hydrolysis and fermentation reactor was proposed as an emerging alternative. In this study, a full-scale pilot testing was performed with side-by-side operation of a conventional anaerobic-anoxic-aerobic (A2O) process versus a S2EBPR process. A comparison of the performance, activity and microbial community between the two configurations was performed. The results demonstrated that, with the same influent wastewater characteristics, S2EBPR configuration showed improved P removal performance and stability than the conventional A2O configuration, especially when the mixers in the side-stream anaerobic reactor were operated intermittently. Mass balance analysis illustrated that both denitrification and EBPR were enhanced in S2EBPR configuration, where return activated sludge was diverted into the anaerobic zone to promote fermentation and enrichment of polyphosphate accumulating organisms (PAOs), and the influent was bypassed to the anoxic zone for enhancing denitrification. A relatively higher PAO activity and total PAO abundance were observed in S2EBPR than in A2O configuration, accompanied by a higher degree of dependence on glycolysis pathway than tricarboxylic acid cycle. No significant difference in the relative abundances of putative PAOs, including Ca. Accumulibacter and Tetrasphaera, were observed between the two configurations. However, higher microbial community diversity indices were observed in S2EBPR configuration than in conventional one. In addition, consistently lower relative abundance of known glycogen accumulating organisms (GAOs) was observed in S2EBPR system. Extended anaerobic retention time and conditions that generate continuous and more complex volatile fatty acids in the side-stream anaerobic reactor of S2EBPR process likely give more competitive advantage for PAOs over GAOs. PAOs exhibited sustained EBPR activity and delayed decay under extended anaerobic condition, likely due to their versatile metabolic pathways depending on the availability and utilization of multiple intracellular polymers. This study provided new insights into the effects of implementing side-stream EBPR configuration on microbial populations, EBPR activity profiles and resulted system performance.

Decision tree for identification and prediction of filamentous bulking at full-scale activated sludge wastewater treatment plant

This study attempted to model sludge bulking in a full-scale wastewater treatment plant operated as a 3-stage Phoredox process. Principal component analysis and a regression tree model were employed to describe the correlations between influent wastewater characteristics and operational conditions (as inputs) and sludge volume index (SVI) as an output. A classification tree model was used to determine the environmental factors that affected the proliferation of filamentous microorganisms. Fluorescent in situ hybridisation analysis identified filamentous species of Microthrix parvicella, Thiothrix I & II, and Eikelboom Types 0041, 0092, and 021 N. It was found that SVI increased with an increment in sludge retention time, but it negatively correlated with soluble chemical oxygen demand (sCOD) and ammonium-nitrogen. The dominance of Microthrix parvicella was observed with a decline in temperature below 15.5 °C, causing an increase in SVI during the winter and spring seasons. The overgrowth of Thiothrix could be linked to the unbalanced ratio between readily biodegradable COD and nutrient species. The filament Type 0092 contributed to high SVI, and it prevailed with a decrease in food-to-microorganisms ratio below 0.08 1/d. Based on the satisfactory training, validation, and generalization procedures, the proposed models could be applied for the prediction of sludge bulking episodes.

Data Mining Application in Assessment of Weather-Based Influent Scenarios for a WWTP: Getting the Most Out of Plant Historical Data

Since the introduction of environmental legislations and directives, the impact of combined sewer overflows (CSO) on receiving water bodies has become a priority concern in water and wastewater treatment industry. Time-consuming and expensive local sampling and monitoring campaigns are usually carried out to estimate the characteristic flow and pollutant concentrations of CSO water. This study focuses on estimating the frequency and duration of wet-weather events and their impacts on influent flow and wastewater characteristics of the largest Italian wastewater treatment plant (WWTP) located in Castiglione Torinese. Eight years (viz. 2009–2016) of historical data in addition to arithmetic mean daily precipitation rates (PI) of the plant catchment area are elaborated. Relationships between PI and volumetric influent flow rate (Qin), chemical oxygen demand (COD), ammonium (N-NH4), and total suspended solids (TSS) are investigated. A time series data mining (TSDM) method is implemented with MATLAB computing package for segmentation of time series by use of a sliding window algorithm (SWA) to partition the available records associated with wet and dry weather events. According to the TSDM results, a case-specific wet-weather definition is proposed for the Castiglione Torinese WWTP. Two significant weather-based influent scenarios are assessed by kernel density estimation. The results confirm that the method suggested within this study based on plant routinely collected data can be used for planning the emergency response and long-term preparedness for extreme climate conditions in a WWTP. Implementing the obtained results in dynamic process simulation models can improve the plant operational efficiency in managing the fluctuating loads.

CO2 addition to increase biomass production and control microalgae species in high rate algal ponds treating wastewater

Challenges regarding microalgal cultivation need to be solved in order to enhance microalgae potential as a feedstock for biofuel, bioenergy, and bioproducts. The optimization of the operating strategy in high rate algal ponds treating wastewater still requires research on microalgal ecosystem response to variations in nutrients availability. For this reason, the aim of this study was to determine the effect of CO2 addition on microalgal population diversity and wastewater treatment performance. To this end, batch and continuous experiments were carried out in an experimental plant constituted by four high rate algal ponds (500 L each) treating urban wastewater with and without pH regulation. As expected, CO2 addition induced a significant increase in biomass concentration (between 66 and 100%). Moreover, a positive effect on microalgal biomass concentration was observed, reducing the effect of the variation in influent wastewater characteristics. Concerning the microalgal populations, the variation of inorganic carbon availability induced a shift in the dominant microalgae species. In spite of this, no variations were observed in terms of wastewater treatment efficiency. Taking together, this study highlighted the positive effect of CO2 addition to increase biomass production and control microalgae species in high rate algal ponds treating wastewater.

Simulation of Oxidation Ditch with STOAT

This paper examines the use of the modified version of ASM model referred to as IAWQ#2B implemented in STOAT simulation package to model the performance of oxidation ditch process. STOAT is a free simulation package for comprehensive modeling and simulation of long-term treatment plants. The dynamic model was calibrated and validated using real operating data from the wastewater treatment plant. The model was able to produce good match in terms of COD, TN, MLSS concentrations, and effluent TSS without adjustment to any default model parameters apart from the wastewater treatment plant operating parameters, and the influent wastewater characteristics which were determined during the data collection campaign. Additionally, the use of chemical polishing for total phosphorus removal (TP) was reasonably predicted by the model. The model was able to identify ‘on-off aeration operation’ as the reason for ammonia spike at the WWTP.

Evaluation of treatment performance of a full-scale membrane bioreactor (MBR) plant from unsteady to steady state condition

A newly installed MBR plant requires domestic sludge inoculation and operation start-up from unsteady state and gradually ends up at steady state condition after the sludge is acclimatized according to influent raw wastewater characteristics. So far, very limited information has been reported in the literature about this initial condition. In this study, treatment performance, sludge characteristics and membrane fouling evaluation of full scale MBR plant was conducted from unsteady to steady state condition. Purpose of the study was to determine an optimum combination of solids retention time (SRT) and flux with desired MLSS range of 8–10–g/L exhibiting excellent treatment performance with good sludge characteristics, and minimum membrane fouling. Membrane fouling at different SRTs was investigated in terms of trans-membrane pressure (TMP). Overall, more than 90% removal of COD was achieved in all combinations of steady state SRTs and fluxes. Complete nitrification (NH4+-N < 1 mg/L) was achieved between 3 and 4 days after startup and NH4+-N remained undetected in effluent throughout the run. PO4−3-P removal of 80% was achieved between 4 and 5 days of startup and remained stable. Sludge characteristics varied at different combinations of SRT and flux combinations. After achieving steady-state, 20 days SRT and 20 LMH flux exhibited the most optimum sludge characteristics and moderate membrane fouling with MLSS between 8 and 10 g/L.

Bacterial community assembly in activated sludge: mapping beta diversity across environmental variables.

Effect of ecological variables on community assembly of heterotrophic bacteria at eight full‐scale and two pilot‐scale activated sludge wastewater treatment plants (AS‐WWTPs) were explored by pyrosequencing of 16S rRNA gene amplicons. In total, 39 samples covering a range of abiotic factors spread over space and time were analyzed. A core bacterial community of 24 families detected in at least six of the eight AS‐WWTPs was defined. In addition to the core families, plant‐specific families (observed at <50% AS‐WWTPs) were found to be also important in the community structure. Observed beta diversity was partitioned with respect to ecological variables. Specifically, the following variables were considered: influent wastewater characteristics, season (winter vs. summer), process operations (conventional, oxidation ditch, and sequence batch reactor), reactor sizes (pilot‐scale vs. full‐scale reactors), chemical stresses defined by ozonation of return activated sludge, interannual variation, and geographical locations. Among the assessed variables, influent wastewater characteristics and geographical locations contributed more in explaining the differences between AS‐WWTP bacterial communities with a maximum of approximately 26% of the observed variations. Partitioning of beta diversity is necessary to interpret the inherent variability in microbial community assembly and identify the driving forces at play in engineered microbial ecosystem.