Influent Quality Research Articles

Model construction and application for effluent prediction in wastewater treatment plant: Data processing method optimization and process parameters integration

Wastewater treatment based on the activated sludge process is complex process, which is easily affected by influent quality, aeration time and other factors, leading to unstable effluent. Facing increasingly stringent sewage discharge standards in China, it is necessary to build a prediction model for early warning of effluent quality. In this study, nine machine learning algorithms were adopted to construct models for the prediction of effluent Chemical Oxygen Demand (COD). In order to improve the prediction accuracy of the models, model optimization was conducted by introducing the hysteresis condition [Hydraulic Retention Time (HRT) of 18 h], data processing method (K-FOLD) and process parameters [dissolved oxygen (DO), sludge return ratio (SRR) and mixed liquid suspended solids (MLSS)]. Results showed that both K-Nearest Neighbour (KNN) and Gradient Boosting Decision Tree (GBDT) displayed excellent prediction effects, the best results of MAPE, RMSE and R2 were 7.34%/1.29/0.92(COD, KNN). The optimized models were further applied to the prediction of effluent total phosphorus (TP), total nitrogen (TN) and pH. The MAPE/RMSE/R2 were 7.43%/0.92/0.93(TN, GBDT), 17.81%/0.19/0.99(TP, KNN), 0.53%/0.16/0.99 (pH, KNN) respectively, indicating high prediction accuracy. The change and comparison of modeling conditions provide a new insight to wastewater prediction models. In addition, this study is close to the actual application scenario of WWTPs operation and management, also laying a foundation for the reverse regulation of energy saving and consumption reduction of wastewater treatment plants (WWTPs).

Bacteriophages in Biological Wastewater Treatment Systems: Occurrence, Characterization, and Function.

Phage bacteria interactions can affect structure, dynamics, and function of microbial communities. In the context of biological wastewater treatment (BWT), the presence of phages can alter the efficiency of the treatment process and influence the quality of the treated effluent. The active role of phages in BWT has been demonstrated, but many questions remain unanswered regarding the diversity of phages in these engineered environments, the dynamics of infection, the determination of bacterial hosts, and the impact of their activity in full-scale processes. A deeper understanding of the phage ecology in BWT can lead the improvement of process monitoring and control, promote higher influent quality, and potentiate the use of phages as biocontrol agents. In this review, we highlight suitable methods for studying phages in wastewater adapted from other research fields, provide a critical overview on the current state of knowledge on the effect of phages on structure and function of BWT bacterial communities, and highlight gaps, opportunities, and priority questions to be addressed in future research.

Evaluation of Al-Thagher Wastewater Treatment Plant

This study aims to evaluate the performance of the sewage treatment plant in Al-Thagher city, in the north of Basrah governorate, the southern part of Iraq. The plant’s performance was estimated based on an analysis of influent and effluent wastewater quality data that represented the monthly averages from Feb. 2017 to Dec. 2018. The results show that the values of temperature (T), pH, ammonia (NH3–N), chemical oxygen demand (COD) and biological oxygen demand (BOD) in all collected samples from the effluent of the plant met the Iraqi water quality standard (IWQS), whereas the values of electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), sulfate (SO4–2), chloride (Cl–1) and phosphate (PO4–P) met the Iraqi water quality standard (IWQS) in some months and did not meet the standard in other months. The average removal efficiencies were in the following order: COD (77.12%) > BOD (77.03%) > TSS (62.26%) > NH3–N (59.99%) > PO4–P (12.42%) > Cl–1 (1.97%). The removal percentages for the remaining parameters had negative values. The Canadian Council of Ministers of the Environment water quality index (CCME WQI) value of the treated water was 51.80 and classified as “marginal.” The coefficients of determination between each parameter in influent or effluent were calculated. Finally, linear regression equations between these parameters were formulated so that the value of one parameter could be used to predict the value of a different parameter.

Feasibility Evaluation of Wastewater Treatment Plant System: A Case Study of Domestic Wastewater System in Sleman Regency, Yogyakarta, Indonesia

Domestic Wastewater Treatment Plant (DWWTP) type 1 and DWWTP type 2 were being evaluated. DWWTP type 1 is located in Sembir area while DWWTP type 2 is located in Tambakrejo area which are both in Sleman Regency, Special Region of Yogyakarta (Daerah Istimewa Yogyakarta or DIY), Indonesia. The emphasis of this research is to choose the manhole material which has the least leakage to the soil, influent discharge performance and wastewater treatment quality effluent. The method used to measure the discharge was by averaging daily discharge for twelve hours, while the E. Coli bacteria under the manhole was also being analyzed. Pollution Index method was also used to evaluate the pollution levels of the wastewater treatment effluent. Results of the study indicated that DWWTP type 1 performance was not optimal because the number of users was greater than that of the design. The impacts were excessive capacity, improper detention time and several parameters of the effluent did not meet the Indonesian legal regulation, including Chemical Oxygen Demand (COD), with efficiency of 34.43%. Wastewater treatment quality effluent parameters which met the Indonesian legal regulation were pH, TSS, TDS, Oil and Grease and Chlorine for DWWTP type 1. Pollution Index (PI) of DWWTP type 1 was 7.02 and PI of DWWTP type 2 was 6.96 which were relatively categorized as moderately polluted. DWWTP type 2 performance was optimal with mean discharge lower than the design discharge. Parameters of the effluent which met the Indonesian legal regulation were pH, TSS, TDS, Oil and Grease, Detergent and COD for DWWTP type 2. The COD of DWWTP type 2 met the Indonesian legal regulation with high efficiency of 73.24%. The E. Coli bacteria was not found in soils under the ring type precast concrete manholes. Hence ring type precast concrete base manhole is recommended.

Total value wall: Full scale demonstration of a green wall for grey water treatment and recycling

Greywater treatment and reuse for non-potable purposes in urban areas has become a widely researched topic to reduce the burden on fresh water resources. This study reports on the use of a green wall for treating grey water and reusing the effluent for toilet flushing, called Total Value Wall (TVW). Initially, the effectiveness of (mixtures of) different substrates, i.e. lava, lightweight expanded clay aggregates, organic soil and biochar was investigated by means of column tests. All substrates were first examined for hydraulic characteristics and later on the columns were fed with synthetic grey wastewater and followed up in terms of removal efficiency of COD and detergents. The mixture consisting of lava (50%), organic soil (25%) and biochar (25%) proved to be optimal both in terms of percolation rates and removal efficiencies, and was thus selected for the full-scale system. The full-scale TVW of 14.4 m2 was installed at a terraced house in Ghent (Belgium), and was loaded with grey water at 100 L per day. Influent and effluent quality were routinely monitored by grab sampling, water savings were monitored by means of flow meters, and electricity consumption was also accounted for. The TVW was further equipped with sensors that measure temperature, Particulate Matter (PM10) and CO2 in the air. The full-scale system obtained effluent concentrations of 13 mg.L−1 TSS, 91 mg.L−1 COD and 5 mg.L−1 BOD5. Ammonium and total coliforms were removed with removal rates of 97% and 99% (2 log units) respectively. However, an increase in effluent concentration of nitrate and phosphate was observed due to leaching from the selected substrate. Available data from the temperature sensors have clearly demonstrated the additional benefit of the TVW as an insulating layer, keeping the heat outside on warmer days, and keeping the heat inside on colder days. Overall, this study demonstrated that the TVW is a sustainable system for greywater treatment and reuse.

Influent Quality and Quantity Prediction in Wastewater Treatment Plant: Model Construction and Evaluation

Influent Quality and Quantity Prediction in Wastewater Treatment Plant: Model Construction and Evaluation

Optimization of Hydrolysis-Acidogenesis Phase of Swine Manure for Biogas Production Using Two-Stage Anaerobic Fermentation

The traditional pig manure wastewater treatment in Taiwan has been low in methane production efficiency due to unstable influent concentration, wastewater volume, and quality. Two-stage anaerobic systems, in contrast, have the advantage of buffering the organic loading rate in the first stage (hydrolysis-acidogenesis phase), allowing a more constant feeding rate to the second stage (methanogenesis phase). Response surface methodology was applied to optimize the operational period (0.5–2.0 d) and initial operational pH (4–10) for hydrolysis and acidogenesis of the swine manure (total solid 5.3%) at 35 °C in batch operation mode. A methanogenesis verification experiment with the optimal condition of operational period 1.5 d and pH 6.5 using batch operation resulted in peak volatile acid production 7 g COD/L, methane production rate (MPR) 0.3 L-CH4/L-d, and methane yield (MY) 92 mL-CH4/g-CODre (chemical oxygen demand removed). Moreover, a two-stage system including a hydrolysis-acidogenesis reactor with the optimal operating condition and a methanogenesis reactor provided an average MPR 163 mL/L-d and MY 38 mL/g volatile solids, which values are 60% higher than those of a single-stage system; both systems have similar dominant methane-producing species of Firmicutes and Bacteroidetes with each having around 30%–40%. The advantages of a two-stage anaerobic fermentation system in treating swine manure for biogas production are obvious.

Dynamic relationship between dissolved organic matter and soluble microbial products during wastewater treatment

Dynamics of the dissolved organic matter (DOM) and soluble microbial products (SMP) significantly affected the sustainability of wastewater treatment plants and effluent qualities. In this study, the origin, transformation, and seasonal variation of DOM components in the anaerobic/anoxic/oxic (A2O) units were illustrated with fluorescence analysis. Results show that the anaerobic process transformed humic acid-like substances (HA) and SMP into fulvic acid-like substances (FA) and aromatic proteins (AP), which indicated the decomposition of macromolecules. In cold seasons, the anoxic process turned AP to HA, SMP, and FA; but the oxic process reversed the transformation. In warm seasons, 6.0% of AP decreased while 3.1% of HA, 1.8% of SMP, and 1.0% of FA increased during the oxic process. Proteobacteria strains were isolated from the activated sludge to stimulate the SMP generation, it was found higher temperature facilitated the transformation of FA and HA (humics) to SMP and AP (proteins), which resulted more proteins presented in the wastewater DOM. These findings indicated that the treatment efficiency and DOM quality in A2O processes were influenced by influent quality and/or temperature conditions, and highlighted the generation of SMP by sludge microorganisms, based on which the corresponding strategies considering the seasonal DOM/SMP dynamics were recommended for the stringent regulation of effluents and the sustainability of the receiving water bodies. Besides, the overall fluorescence intensity was positively correlated with the quantified biopolymer contents in SMP, implying the potential of using the fluorescence-derived information to indicate more quantified DOM properties.

Intelligent sensor validation for sustainable influent quality monitoring in wastewater treatment plants using stacked denoising autoencoders

Wastewater treatment plants (WWTPs) influent conditions can dramatically affect a treatment unit's state and effluent quality. WWTP sensors may record faulty measurements due to abnormal events or the malfunction of the system, leading to serious problems in the system's operation and the violation of effluent discharge standards. Therefore, automatic fault detection and faulty data reconciliation are crucial for an efficient and stable WWTP monitoring. In this study, a holistic framework for sensor validation of WWTP influent conditions is presented considering the non-linearity, measurement noise, and complexity of the WWTP's data. A stacked denoising autoencoder (SDAE) model is proposed to detect, identify, and reconcile faulty data based on data from a real WWTP in South Korea. The proposed SDAE architecture presented a detection rate (DR) between 74% and 98%. The faulty sensor was identified using an SDAE-based sensor validity index (SVI). Data reconciliation showed that the SDAE was the most suitable reconciliation method based on the root mean square error (RMSE) for total nitrogen (TN) influent conditions of 4.04 mg N/L. Finally, faulty, noisy, and reconciled measurements were evaluated in a WWTP model to determine the proposed method's resilience potential.

Estimating effluent turbidity in the drinking water flocculation process with an improved random forest model

AbstractDuring drinking water treatment, the uncertain changes of raw water quality bring great difficulties to the control of flocculant dosage, especially because the feedback information based on the effluent turbidimeter of the sedimentation tank can only be obtained after a long time when the influent water quality changes due to the large lag characteristics of the flocculation process. Prediction of effluent turbidity of the sedimentation tank can effectively solve the aforementioned problem. Given that it is difficult for the ordinary random forest (RF) model to accurately predict the effluent turbidity of a sedimentation tank for complicated changes of raw water quality, an improved random forest (IRF) model composed of long-term and short-term parts is proposed, which can capture the periodicity and time-varying characteristics of influent water quality data. The experimental results show that the root mean square error and mean absolute percentage error of IRF model in Baiyangwan waterworks are improved 67.52% and 67.91% respectively, compared with those of the ordinary RF model. The proposed effluent turbidity predictions are also successfully developed in Xujiang waterworks and Xiangcheng waterworks of Suzhou, China. This research provides an effective method for real-time prediction of the effluent turbidity of sedimentation tank according to the influent water quality data.

Nitrogen removal performance and microbiological characteristics of a three-stage series of vertical flow constructed wetlands.

In this study, the treatment performance and underlying molecular mechanisms of nitrogen transformation in a three-stage series of vertical flow constructed wetlands (T-VFCWs) treating rural domestic sewage were investigated at three different hydraulic loading rates (HLRs). Specifi-cally, the T-VFCWs composed of three sequential vertical flow constructed wetlands (termed V-1, V-2 and V-3), which were built according to the topography. The results showed that high pollutant removal rates could be achieved when the T-VFCWs was operated to treat rural domestic sewage, even though the HLR increased from 0.10 to 0.20 m3·m-2·d-1. Effluent quality of the T-VFCWs could reach Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002) class A standard. Regarding to the T-VFCWs operated under the oxygen-limiting conditions, three different pathways for nitrogen transformation could be respectively formed in V-1, V-2 and V-3, owing to the specific influent quality of each subunit. Consequently, the T-VFCWs were effective in nitrogen removal as a result of the collaboration of the three subunits. When the T-VFCWs ran constantly during the test, nitrogen removal in V-1, V-2, and V-3 respectively relied on the nitritation/denitrification process, the completely autotrophic nitrogen removal over nitrite (CANON) process, and the denitrification process. The contributions of three subunits for total nitrogen (TN) and NH4+-N removal were (51.3±4.4)% and (63.7±2.6)%, (30.9±4.8)% and (35.5±4.5)%, (17.8±5.0)% and (0.8±0.1)%, respectively. This study could provide scientific basis and technical support for the research and the engineering application of hybrid constructed wetlands.

분리막 전처리공정인 사여과층의 여과성능평가

Membrane fouling due to the accumulation of natural organic matter, inorganic components and colloidal/particulate matter on the surface and/or in the pores of the membrane decreases the membrane permeability and therefore impedes the implementation and efficient performance of membranes in the production of drinking water regardless of influent water quality. The objective of this study was carried out to investigate the operating conditions of sand filteration (SF) influencing the permeability performance and fouling of membrane filtration (MF) processes. Applied filtration rates during this experiment were <120 m/d for the SF and 0.5 ㎥/㎡.d for MF. Influent concentration were on average turbidity <130 ntu and total organic carbon (TOC) <11 mg/L. As a result, both SF process and SF/MF system achieved the efficiencies of more than 90% in removing turbid matter, while the removal efficiency of TOC were 10-30% for SF process and 40-60% for SF/MF system. The SF/MF system achieved 2 times higher than that of SF process in removing TOC due to biofiltration by the bio-cake layer formed on the surface of media. For transmembrane pressure (TMP), TMP increasing rate of MF was in proportion to an increasing rate of turbid and organic matters. These results indicate that the introduction of the biofilm sand filter prior to MF process is necessary for membrane fouling mitigation.

Performance evaluation of aerobic fluidized bed bioreactor coupled with tube-settler for hospital wastewater treatment

The need for wastewater treatment does not only arise from an environmental conservation point of view. But also, from the fact that it can be reused for secondary proposes. The most of hospitals being present in urban space, still their wastewater treatment are not fully explored. The Fluidized Aerobic Bed Bioreactor (FABB) treats wastewater in a liquid-solid phase among various wastewater treatment processes. This study employed a fluidized aerobic bed reactor coupled with a tube settler for hospital wastewater treatment. The treatment efficiency was evaluated based on the removal of pollutants and nutrients with associated parameters pH, Alkalinity, total suspended solids (TSS), and mixed liquor suspended solids (MLSS). The efficiency was determined by evaluating the influent and effluent quality of samples. The BOD5 was reduced at an average of 69% in FABB, and for tubesettler, it resulted in consumption of only 39%. Similar types of results were obtained when considering it for COD, i.e., 72% and 38%, respectively, for FABB and tube settler. The nitrification was observed in both nitrate accumulation by 103% and 3.65% in FABB and tube settler. In the absence of anaerobic conditions, the denitrification process could not be achieved. Hence the cycle was not completed. Lower phosphate reduction was achieved, 63% and 23%, however concentration in influent were below the permissible limit of 5 mgL−1. The study concludes that FABB can be successfully employed for hospital wastewater treatment. Additionally, tubesettler may be used in place of a secondary clarifier in the treatment of hospital wastewater.

Laboratory Efficacy of Locally Available Backwashing Methods at Removing Fouling in Hollow-Fiber Membrane Filters Used for Household Water Treatment.

Hollow-fiber membrane filters (HFMFs) for household water treatment (HWT) can efficaciously remove disease-causing organisms in laboratory settings. However, lower effectiveness in use in low- and middle-income countries (LMICs) and humanitarian contexts (HCs) has been observed and attributed to membrane fouling and the associated cleaning. In LMICs/HCs, it is not possible to prevent and control fouling using commonly known methods (e.g., testing influent water, maintenance regimes), and the literature on fouling/cleaning of HFMFs distributed in LMICs is scarce. As such, controlled laboratory experiments were conducted to determine the efficacy of locally available (in LMICs/HCs) backwashing solutions at removing fouling using different influent waters and HFMF types. Four commonly distributed HFMFs were selected; fouling layers were developed by filtering three influent water compositions, representing LMIC/HC waters, for 10-days, and bleach, water, or vinegar backwashing solutions were used for daily backwashing. Filter performance indicators included: fiber mechanical properties (strain at break, break force), water quantity performance (flow), water quality performance (turbidity, E. coli), and imaging. The study found fouling developed rapidly and altered mechanical properties and water quantity indicators within 200 h of filtration. Fouling did not decrease water quality indicators. Backwashing improved the filter’s mechanical properties and water quantity performance, but it did not fully recover the initial performance. Additionally, recovery differed between backwashing solutions, and no universal cleaning recommendation appropriate for HFMFs in LMICs/HCs was identified. Overall, fouling development and control depended on HFMF type, influent water quality, and backwashing solution type; thus, caution before distributing HFMFs for long-term use in LMICs/HCs is recommended.

Effect of operating mode on the performance of sand filters treating greywater.

A long-duration laboratory study spanning more than 6 months was conducted to evaluate the effect of operating mode on the performance of sand filters for greywater treatment. Performance of saturated and unsaturated filters operated in continuous or intermittent mode was evaluated using settled real greywater. Effects of pause period and higher loading rate on their performance were also evaluated. Furthermore, the effect of the depth of the filter medium on the performance of the filters was also assessed. The saturated filters operated continuously or intermittently performed significantly better than the respective unsaturated filters. Saturated continuous (SC) and unsaturated intermittent (UI) filters were the best and worst performers amongst the different filters. SC filter removed on an average 98% turbidity, 76% BOD, 88% COD, 84% ammonia-N (NH4-N) and 95% phosphate (PO4-P). Up to 99.68% (2.40 log) removal of faecal coliforms was also achieved by this filter. SC filter showed stable and reliable performance as its effluent quality was insensitive to fluctuations in influent quality. The pause period significantly affected the removal of some of the parameters. Doubling the hydraulic loading rate significantly affected the performance of continuous filters. Though most of the pollutant removal occurred in the top 10 cm in all the filters, a depth of 50 cm was found optimum for the removal of different pollutants. Whilst all the filters produced effluent conforming to different reuse standards except microbial standards, saturated continuous filter (SC) could also meet the faecal coliform standards towards the end of the filter operation.

Combined coagulation and intermittent sand filtration for on-site treatment of greywater

Performance of coagulation followed by intermittent saturated sand filtration system was evaluated for greywater treatment using real greywater. Filters with two different grain sizes were used to study the effect of media size on the removal. Filters were charged daily with 20 L of greywater coagulated with polyaluminium chloride (PACl). Performance of the filters were evaluated based on physicochemical and microbial parameters. Results showed that coagulation followed by sand filtration resulted in 94, 76 and 80% reduction in turbidity, BOD and COD respectively. Also, more than 99% of total and faecal coliform removal was observed. Sand filter with smaller grain size performed significantly better than the sand filter with coarser grain size. Coagulation followed by filtration showed stable and reliable performance as the effluent quality was insensitive to fluctuations in influent quality. Combined coagulation and sand filtration produced effluent conforming to different reuse standards.

Removal of Turbidity and Assessment of Groundwater Contribution during Riverbank Filtration

Indian rivers carry large sediment loads. During monsoon season when river discharge is high, rivers carry suspended particles, silt, clay, and organic substances, causing river water turbidity that is not suitable for drinking. Riverbank filtration (RBF) is a natural process in which one can abstract good quality water from a highly polluted river through abstraction wells. As RBF water is a mixture of riverbank filtered water and groundwater, assuming no turbidity was picked up by the river water as it travelled through the soil matrix to reach the pumping well. A strategy-A was developed in which flow of groundwater contribution toward pumping well was neglected, while simultaneously measuring source water and abstracted water quality; it was observed that the variation of K, the kinetic coefficient, captured the variation in ln(C0), natural logarithm of influent quality, with R2 equal to 0.974. The kinetic coefficient, K, also captured the variation with ln(C0) of turbidity after travel times of 14 days and 21 days, having R2 equal to 0.991 and 0.989, respectively. A strategy-B was developed using the mass balance relationship, wherein the flow of groundwater contribution toward pumping well was utilized in refining the abstracted water quality. It was observed that K, the kinetic coefficient, of strategy-B captured the variation with ln(C0), the natural logarithm of the influent quality of turbidity with R2 equal to 0.972. If both the strategies were to be compared, strategy-B was found to be superior to strategy-A. However, one additional data of measurement on the groundwater turbidity was required for strategy-B. Further, strategy-C was developed with the assumption that there was no turbidity in groundwater, as a low value of turbidity was observed in groundwater. The variation of K, the kinetic coefficient, with ln(C0), the natural logarithm of influent quality of turbidity in strategy-C, showed that when the groundwater turbidity was ignored, the agreement between observed and computed turbidity was adversely affected. The average contribution of groundwater toward pumping well was observed nearly 12.43% and the average contribution of river water toward the pumping well was observed nearly 87.57%, considering the depth of river water. In strategy-C also, the agreement between simulated and observed values of turbidity was satisfactory.

“Gully pit inserts” shown to reduce pollutants in stormwater

‘Gully pit inserts’ (or ‘gully baskets’) are a commonly applied stormwater control measure given they can often be easily integrated into gully pits with no impact to the usability of the area. Stormwater treatment performance monitoring has been undertaken for a gully pit with a fine grade (200-micron) bag of 300mm depth in a car-park in Western Sydney, NSW, Australia. The gully pit insert receives runoff from a 100% impervious car-park area of 400m2. Influent and effluent water quality samples were collected using automated samplers, which were connected to pre-configured and calibrated flow analysis of treated effluent and sample pacing with remote communication and data access. Collected samples were delivered to and analysed in a NATA-accredited laboratory for pH and concentrations of suspended solids and nutrient species. Monitoring was undertaken between December 2019 and March 2021, with a total of fifteen (15) runoff events recorded during this period. The performance testing demonstrated that the gully pit insert was able to achieve significant reductions in stormwater pollutant concentrations, with a concentration reduction efficiency ratio for total suspended solids, total phosphorus and total nitrogen of 52, 67 and 41% respectively.

Economic Model Predictive Control for optimal struvite recovery

Resource recovery from municipal wastewater has been a prime focus for a decade. Although several recovery processes already exist in the market today, the high cost of material, inherent disturbance in the influent quality, lack of real time monitoring of critical parameters, and lack of a robust automation system may result in suboptimal performance. This work attempts to construct a model based predictive control for optimal operation of a struvite recovery unit in a full scale WRRF. A multi-parameter based predictive control has been developed by implementing an Economic Model Predictive Controller (EMPC) for optimal dosing of magnesium hydroxide in a struvite recovery unit. The EMPC used customized objective function for real-time optimization of performance and economical parameters of the crystallization unit. The effectiveness of the proposed EMPC controller is verified through tests conducted on the Benchmark Simulation Model No. 2 (BSM2d.). The results obtained from the simulator-based evaluation of EMPC demonstrate a significant improvement in resource recovery at reduced operational costs. The economic advantages of implementing an EMPC compared to proportional and constant magnesium dosage has also been enumerated.

Treatment of real domestic sewage in a pilot-scale aerobic granular sludge reactor: Assessing start-up and operational control.

Aerobic granular sludge (AGS) has been considered a breakthrough in the wastewater treatment sector given its key characteristics, such as excellent settleability, simultaneous removal of organic and nutrient pollutants, and compactness. However, the formation of granules often delays the start-up of granular-based systems, especially in large-scale settings. This study addressed the start-up of a pilot-scale AGS sequencing batch reactor (SBR) treating domestic sewage, monitored for over 280days. The challenges faced during aerobic granulation using a mixture of activated sludge and anaerobic granular sludge as inoculum and the performance of the reactor on organic matter, nitrogen, and phosphorus removal were discussed. Results showed that robust and stable granules were formed after an initial period of around six months, with the settling time playing a key role on granules development. At least 80% of granules had a diameter greater than 0.2mm and 60% >1mm. In general, the reactor achieved high nitrogen removal efficiency, as well as satisfactory removal of soluble COD. However, total COD abatement was impaired by the various episodes of suspended solids loss with the effluent. Overall, this study demonstrated that the reactor was efficient in the treatment of domestic sewage, but its performance was adversely affected from sudden changes in the influent quality. PRACTITIONER POINTS: Aerobic granular sludge (AGS) applied to small-scale domestic sewage treatment. The control of sludge age in AGS can be a problem due to short sedimentation times. High DO to maintain aerobic granulation can economically make the process economically unfeasible in tropical countries. A sludge with excellent sedimentation properties was obtained. However, maintaining the granule over time is a challenge.