Raw Municipal Wastewater Research Articles

Municipal wastewater treatment using an innovative two-stage sequential microalgal co-cultivation system with different hydraulic retention time: A sustainable approach to circular economy

The present study proposes a sustainable circular bioeconomy approach for municipal wastewater (MWW) treatment, employing a sub-pilot two-stage sequential microalgal co-cultivation system (TSSCS), and evaluates the impact of hydraulic retention time (HRT) on MWW treatment efficiency, as well as biomass and biomolecule productivity. In the first stage of TSSCS, 2 ratios of Tetraselmis indica and one ratio of Picochlorum sp. (2TS:1PC) were used for the treatment of 75% raw MWW + 25% ASN-III, while in the second stage, 2PC:1TS was employed for the treatment of 50% 2TS:1PC effluent+ 50% ASN-III. At the end of the first and second stages of TSSCS, nutrient removal efficiencies were as follows: total nitrate (TN) was <80% and 90% on HRT-10 and HRT-12; total phosphate (TP) was <85% and 95% on HRT-16, and chemical oxygen demand (COD) was <75% and <85% on HRT-14 and HRT-10, respectively. In the TSSCS, 2TS:1PC (S1) and 2PC:1TS (S2) showed maximum biomass productivity of 2.65 and 2.78g/L on /L on HRT-14 and HRT-12, respectively. Additionally, biomass of 2TS:1PC (S1) and 2PC:1TS (S2) contains lipid content (38.67 and 40.67%), β-carotene (4.09 and 3.00mg/g), and astaxanthin (0.69 and 0.31mg/g), respectively.

Building a simple multivariable filtration model to predict irreversible fouling when directly filtering municipal wastewater

This paper describes a simple generic model designed to predict membrane fouling in municipal wastewater (MWW) treatment. The work was conducted using data from a direct membrane filtration demo-system (middle/long-term filtration periods of about 35 – 124 days) to calibrate the model. Two influents were treated by the demo-system: raw pre-treated MWW and primary settler supernatant from a full-scale MWW treatment plant. A resistance-in-series mathematical model structure was proposed considering fouling due to two different mechanisms: persistent cake layer formation (from suspended material) and pore blocking (from soluble and colloidal compounds). The proposed model represented transmembrane pressure dynamics at different operating solids concentrations (around 1, 2.6, 6 and 11 gL−1) using 7 model parameters, achieving 7–28 mbar differences between the experimental data and model predictions in all cases (calculated as the root mean square error). The model was also able to match the results from two different influents (raw MWW and primary settler supernatant) by modifying 3 of the 7 parameters while low uncertainties were obtained in long-term filtrations, demonstrating its robustness. This model thus provides a good potential to generate reasonable membrane fouling predictions while its simple and open structure makes it easy to implement with complementary materials. Further research will be carried out to enhance the model’s precision and validate its potential for optimizing filtration and fouling control processes.

Performance evaluation and parameter estimation of the advanced primary filtration (APF) process in wastewater treatment plants

Conventional technologies employed in wastewater treatment plants (WWTPs) demand significant energy consumption. Concurrently, the wastewater infrastructure is experiencing a heavy strain as a result of the increased influent loads and pollutants. Advanced primary filtration (APF) is an emerging wastewater treatment process for early removal of suspended solids from raw wastewater. In this work, the APF process comprises of a two-stage filtration system, consisting of a proprietary rotating belt filter (RBF) (collectively known as microsieve) followed by a proprietary continuous backwash upflow media filter (CBUMF). The principal focus of this study is the assessment of the APF process performance, and the prediction of the total suspended solids (TSS) effluent concentrations of the APF process, using a parameter estimation method. According to pilot scale experimental results, the percentages of TSS (average TSS removal rate of 51 %) and biological oxygen demand (BOD5) (average BOD5 removal rate of 30 %), removed by the microsieve were notably higher compared to conventional primary treatment (sedimentation). The removal efficiency of the APF process during stable operation, varied from 69 to 86 % for TSS, as compared to 50–70 % typically achieved with primary sedimentation. The removal performance of BOD5 varied from 44 to 82 %, as compared to 25 to 40 % typically achieved with primary sedimentation. The chemical oxygen demand (COD) removal rates for the APF process ranged between 62 and 90%, as compared to 25–40 % typically achieved with primary sedimentation. The early removal of TSS prior to aeration tank has the potential to significantly enhance the capacity of the WWTP and decrease the energy requirements of the aeration tank. A high degree of concordance between model predictions and experimental data was observed. This study demonstrated the potential of using the APF process for the early removal of TSS from raw municipal wastewater just upstream of the aeration tank.

Insight into performance of nitrogen removal enhanced by adding lactic acid-rich food waste fermentation liquid as carbon source in municipal wastewater treatment

Lactic acid-rich fermentation liquid (LAFL) of food waste is found to act as a promising alternative carbon source for nitrogen removal in wastewater treatment. Here, LAFL was employed to investigate its impacts on nitrogen removal during raw municipal wastewater treatment with a comparison to sodium acetate (NaAc). Results indicated that nitrogen removals were comparable when incorporated with LAFL and NaAc (92.89 % v.s. 91.23 %). Unlike the utilization of NaAc, using LAFL could avoid suppressing the relative abundance of the nitrification genes and thus pose a negative risk to nitrogen removal during prolonged operation. The introduction of LAFL increased the stability and robustness of the functional microbial community and effectively reduced excess activated sludge (AS) generation by 109 % compared to NaAc addition, consequently enhancing nitrogen removal but diminishing the treatment cost. In general, LAFL exhibits prospective engineering application potentials and economic advantages in improving nitrogen removal by AS process.

Fungi-assisted bio-flocculation of Picochlorum sp.: A novel bio-assisted treatment system for municipal wastewater

Integration of microalgal cultivation with wastewater reclamations are sustainable valorizations approach to nutrients removal and lipid-rich biomass production. Lower growth rates and higher harvesting costs are the major bottlenecks of algal-based wastewater treatment process. Therefore, this study was carried-out to investigate lipid-rich biomass production using wastewater and demonstrate the low-cost biomass harvesting method. Picochlorum sp. BDUG 100241 (PC) was explored in various combinations of untreated raw municipal wastewater (UTMWW) and secondary treated municipal wastewater (STMWW) with a conventional ASN-III medium. The day-night cycles, pH, and aeration were optimized to improve PC biomass production. For harvesting of PC biomass, different concentrations of filamentous fungi Aspergillus niger MTCC 281 (A. niger) and Stropharia sp. ITCC-8422 assisted bioflocculation approach was investigated. In the first phase of optimization, PC showed maximum nutrient removal efficiency and growth in 50 % STMWW +50 % ASN-III. The present results indicated that a 12:12 h day-night cycle and a pH of 7.0 with aeration resulted in the highest nutrient removal efficiency of COD (90.92 %), phosphate (92.26 %) and nitrate (87.20 %). This optimized conditions also improved the biomass production (2.66 g/L), lipid content (44.04 %), photosynthetic and carotenoids (astaxanthin and β-carotene) production. Further, 10 % Stropharia sp. and A. niger granulated pellets signified the bioharvesting of PC biomass with maximum bioflocculation efficiency of 90.15 % and 92.48 %, respectively. The incorporation of bioflocculants, namely Stropharia sp. and A. niger for the harvesting of microalga biomass facilitated the removal of nutrients, enhanced biomass production (4.21 and 4.01 g/L), and augmented lipid content (43.0 % and 47.33 %) respectively.

Novel eco-friendly polylactic acid nanocomposite integrated membrane system for sustainable wastewater treatment: Performance evaluation and antifouling analysis

Water contamination caused by heavy metals, nutrients, and organic pollutants of varying particle sizes originating from domestic and industrial processes poses a significant global challenge. There is a growing concern, particularly regarding the presence of heavy metals in freshwater sources, as they can be toxic even at low concentrations, posing risks to human health and the environment. Currently, membrane technologies are recognized as effective and practical for treating domestic and industrial wastewater. However, these technologies are hindered by fouling issues. Furthermore, the utilization of conventional membranes leads to the accumulation of non-recyclable synthetic polymers, commonly used in their production, resulting in adverse environmental consequences. In light of our previously published studies on environmentally friendly, biodegradable polylactic acid (PLA) nanocomposite mixed matrix membranes (MMMs), we selected two top-performing PLA-based ultrafiltration nanocomposite membranes: one negatively charged (PLA-M−) and one positively charged (PLA-M+). We integrated these membranes into systems with varying arrangements to control fouling and eliminate heavy metals, organic pollutants, and nutrients from raw municipal wastewater collected by the local wastewater treatment plant in Abu Dhabi (UAE). The performance of two integrated systems (i.e., PLA-M+/PLA-M− and PLA-M−/PLA-M+) was compared in terms of permeate flux, contaminant removal efficiencies, and fouling mitigation. The PLA-M+/PLA-M− system achieved removal efficiencies of 79.6 %, 92.6 %, 88.7 %, 85.2 %, 98.9 %, 94 %, 83.3 %, and 98.3 % for chemical oxygen demand (COD), nitrate (NO3−-N), phosphate (PO43−-P), ammonium (NH4+-N), iron (Fe), zinc (Zn), nickel (Ni), and copper (Cu), respectively. On the other hand, the PLA-M−/PLA-M+ system recorded removal efficiencies of 85.8 %, 95.9 %, 100 %, 81.9 %, 99.3 %, 91.9 %, 72.9 %, and 98.9 % for COD, NO3−-N, PO43−-P, NH4+-N, Fe, Zn, Ni, and Cu, respectively. Notably, the PLA-M−/PLA-M+ system demonstrated superior antifouling resistance, making it the preferred integrated system. These findings demonstrate the potential of eco-friendly PLA nanocomposite UF-MMMs as a promising alternative to petroleum-based polymeric membranes for efficient and sustainable wastewater treatment.

Coupling AnMBR, Primary Settling and Anaerobic Digestion to Improve Carbon Fate When Treating Sulfate-Rich Wastewater

The present work involved an assessment of the technical feasibility of coupling AnMBR, primary settling and anaerobic digestion to treat sulfate-rich wastewater at ambient temperature. The innovative approach used focused on reducing the carbon footprint of wastewater treatment while maximizing the energy recovered from influent organic matter. In this process, primary settling reduces the COD/SO4-S ratio in the influent of the AnMBR system and completely removes organic matter by sulfate-reducing bacteria (SRB), while increasing the COD/SO4-S ratio in the sidestream anaerobic digester (AD), enhancing energy recovery and biogas quality. This approach has the significant advantage of only producing methane in the AD, so that the AnMBR produces a high-quality, methane-free effluent with no environmental impact from fugitive methane emissions. The performance of this treatment scheme was assessed by operating a demonstration-scale AnMBR plant fed by primary settled municipal wastewater at the hydraulic retention times of 25, 12 and 8.5 h. The results showed that the COD and BOD removed by SRB enabled setting the discharge limits at 25 and 12 h and lowered the carbon footprint to levels below those of an AnMBR plant fed by raw municipal wastewater, mainly by eliminating fugitive methane emissions.

Achieved advanced wastewater phosphate removal via improved ionic interference resistance in a migration-electric-field assisted electrocoagulation (MEAEC) system with modified-biochar pseudocapacitor electrode

The capacitive deionization-assisted electrocoagulation system has promising application potential in advanced phosphate removal of its low electricity consumption and sacrificial anode material. Phosphate removal in wastewater is crucial since excess phosphate might lead to eutrophication. However, the complex ion composition in raw wastewater can influence the effective phosphate removal by competing with the precipitable metal ions during electrocoagulation. In this study, a novel migration electric-field assisted electrocoagulation (MEAEC) with an assisted capacitive electrode made of N-doped and Fe-La co-modified biochar (LFNB) to achieve specific phosphate electro-adsorption for effective advanced phosphate removal. The LFNB-MEAEC achieved ultrahigh phosphate removal with the effluent of 0.1 mg/L in synthetic and raw municipal wastewater and met the first Grade A standard of total phosphate in the discharge standard of pollutants for municipal wastewater treatment plant (DSPMWTP) in China. The commonly observed coexisting ions in wastewater and a pH range of 2–12 did not significantly fluctuate the phosphate removal of LFNB-MEAEC. Cyclic voltammetry and charging-discharging tests confirmed the high phosphate affinity and excellent durability of LFNB in ion-interference circumstances. The MEAEC assisted with selective-adsorption capacitive electrodes and provided an effective and practical method for advanced phosphate removal from low-phosphorus-contaminated wastewater. The MEAEC with a selective-adsorbed capacitive electrode improved phosphate removal by 21 % (from 74 ± 1.7% to 95 ± 1.0%), reduced the energy consumption by 65.7% (0.012 kWh m−3-wastewater), and saved the sacrificial anode material by 67.5% (from 200 to 65 g m−3-wastewater) than those of MEAEC without phosphate-selective electrode in the same period (Sacrificial anode working time 200 s).

Short-term effect of reclaimed wastewater quality gradient on soil microbiome during irrigation

To investigate the effect of wastewater (WW) treatment on soil bacterial communities, water of different quality was used to irrigate eight lettuces per tank: raw municipal wastewater (RWW), WW treated with an aerated constructed wetland (CWW) and WW treated with a membrane bioreactor (MBW), and tap water (TW). The physicochemical and microbiological characteristics (quality indicators) of these water types were characterized, and the water and soil bacterial communities were monitored by quantitative PCR (qPCR) and 16S rRNA gene sequencing. Despite marked differences in microbial load and diversity of waters, soil communities remained remarkably stable after irrigation. Microbial biomass was increased only in soils irrigated with RWW. At the end of the irrigation period (day 84), soil and water shared a large fraction of their bacterial communities, from 43 % to 70 %, depending on the water quality, indicating a transfer of bacterial communities from water to soil. Overall, the relative abundance of Proteobacteria and Acidobacteria was increased and that of Actinobacteria was decreased in soils irrigated with MBW, CWW and even more with RWW. Multivariate ordination clearly separated soils in three groups: soils irrigated with the cleanest water (TW), with treated WW (MBW and CWW), and with untreated WW (RWW). Nitrifying, denitrifying, and nitrogen-fixing bacteria were quantified by qPCR targeting amoA, narG, and nifH, respectively. Nitrifying bacteria were the most affected by the water quality, as indicated by amoA copy number increase in RWW-irrigated soil and decrease in CWW-irrigated soil. Overall, the abundance of all three genes was positively influenced by RWW treatment. In conclusion, the 84 days of irrigation influenced the soil microbial communities, and the impact depended on the quality of the used water.

Revealing the fouling characteristics in membrane-based primary treatment (MPT) of municipal wastewater and the antifouling mechanism of influent conditioning

Membrane-based technology is becoming an attractive option for primary treatment of municipal wastewater (MW) due to its superior organic retention capacity and footprint savings. However, limited understanding of fouling mechanisms still hampered its practical application. This study aims to investigate the fouling characteristics in MPT and analyze anti-fouling mechanisms of influent conditioning. In the meantime, the differences between microfiltration (MF) and ultrafiltration (UF) are also discussed. Dozens of filtration experiments with different membranes (0.1 μm and 100 kDa), MW conditioning methods (coagulation and adsorption) were conducted. Results indicated that a hallmark of MPT is the protective ability of particulate matters present in the raw MW. The irreversible fouling rate was 2–4 times higher in the absence of particulates. Besides, the main irreversible foulant types and the cake growth patterns differed with different pore sizes. As for influent conditioning, coagulation and adsorption collaborate effectively in regulating cake characteristics. Polymeric aluminum chloride reduces the tendency of binding between foulants and membrane, while activated carbon increases the porosity of the cake layer.

Evaluating resource recovery potential and process feasibility of direct membrane ultrafiltration of municipal wastewater at demonstration scale

The aim of this work was to assess the feasibility of applying ultrafiltration membranes for the direct filtration of municipal wastewater. The effect of different influents (raw wastewater and the primary settler effluent of a municipal wastewater treatment plant) and operating solids concentration (about 1, 2.6, 6 and 11 g L−1) was evaluated. Increasing the operating solids concentration sharply reduced membrane fouling, achieving a minimum of about 0.55 mbar per day when operating above 6 g L−1. Filtering raw municipal wastewater also had a beneficial effect on the filtration performance, although only when operating at a low solids concentration (under 2.6 g L−1). High quality permeates were obtained regardless of operating conditions, meeting European discharge requirements for no sensible environments. High resource recoveries were achieved thanks to the direct filtration of wastewater, capturing about 80-85 and 20%–40% of the influent COD and nutrients, respectively. The energy and carbon footprint balances showed promising results, achieving energy recoveries and carbon footprints of about 0.46-0.40 kWh per m3 of influent municipal wastewater and -[0.19-0.16] kg CO2-eq per m3 of influent municipal wastewater when considering the process energy demands and potential energy recovery. Additionally, profits can be obtained from MWW treatment by this alternative, achieving about €0.035–0.021 per m3 of influent MWW when operating at a flux of 10 LMH which entail a payback period for the initial membrane acquisition of 12.3–20.1 years.

Assessing the impact of a major electronic music festival on the consumption patterns of illicit and licit psychoactive substances in a Mediterranean city using wastewater analysis

The consumption patterns of five categories of psychoactive substances (PS), including “conventional” illicit drugs, new psychoactive substances (NPS), therapeutic opioids, alcohol and nicotine, were studied in the city of Split, Croatia, using wastewater-based epidemiology (WBE), with an emphasis on the impact of a large electronic music festival. The study involved the analysis of 57 urinary biomarkers of PS in raw municipal wastewater samples collected in three characteristic periods, including the festival week in the peak-tourist season (July) and reference weeks in the peak-tourist season (August) and the off-tourist season (November). Such a large number of biomarkers allowed the recognition of distinct patterns of PS use associated with the festival, but also revealed some subtle differences between summer and autumn seasons. The festival week was characterized by markedly increased use of illicit stimulants (MDMA: 30-fold increase; cocaine and amphetamine: 1.7-fold increase) and alcohol (1.7-fold increase), while consumption of other common illicit drugs (cannabis and heroin), major therapeutic opioids (morphine, codeine and tramadol) and nicotine remained rather constant. Interestingly, NPS and methamphetamine clearly contributed to the festival PS signature in wastewater, but their prevalence was rather low compared to that of common illicit drugs. Estimates of cocaine and cannabis use were largely consistent with prevalence data from national surveys, whereas differences were found for typical amphetamine-type recreational drugs, particularly MDMA, and for heroin. The WBE data suggest that the largest proportion of morphine came from heroin consumption and that the percentage of heroin users seeking treatment in Split is probably rather low. The prevalence of smoking calculated in this study (30.6 %) was consistent with national survey data for 2015 (27.5–31.5 %), while the average alcohol consumption per capita >15 years (5.2 L) was lower than sales statistics suggest (8.9 L).

Advanced oxidation processes for pharmaceutical degradation and disinfection of wastewater: peracetic acid and graphene oxide quantum dots

A combination of graphene oxide quantum dots and peracetic acid (GQDs/PAA) was used to degrade sulfasalazine in municipal wastewater. The impact of reaction parameters such as initial concentrations of oxidant (peracetic acid) and drug (sulfasalazine) and different water matrices was evaluated. The degradation efficiency when using GQDs/PAA (50 mg/L: 0.10 mM) was almost 100% in synthetic water and 80% in municipal wastewater. The primary reactive radicals that caused the degradation of sulfasalazine in wastewater were identified as hydroxy (·OH) as well as the peroxy radicals (CH3C(=O)OO·, CH3C(=O)O·). 83.7% of total organic carbon were eliminated when 0.15 mM PAA was used while nearly 100% degradation of SZZ was achieved. A degradation pathway was proposed using the degradation intermediates obtained on quadrupole time-of-flight liquid chromatography mass spectrometry. The genotoxic and mutagenic potential of the degradation products formed during the degradation of sulfasalazine was assessed using the Ames test. It was demonstrated that none of the intermediates were mutagenic. GQDs/PAA was further tested as a potential disinfectant, and S. aureus was completely inactivated as verified by using LIVE/DEAD Baclight staining. In raw municipal wastewater, GQDs/PAA eliminated more than 90% of bacteria, thus confirming the synergy of GQDs/PAA as both a disinfectant and a photocatalyst.

In situ surface modification of forward osmosis membrane by polydopamine/polyethyleneimine-silver nanoparticle for anti-fouling improvement in municipal wastewater treatment.

In this work, we demonstrate the surface functionalization of cellulose triacetate membrane with co-deposition of polydopamine (PDA)/polyethyleneimine (PEI) and silver nanoparticles (AgNPs) for antifouling property in municipal wastewater treatment. PDA/PEI was first coated on the membrane surface by single-step co-deposition, while AgNPs were formed in situ through catechol groups of PDA immobilizing silver ions and subsequently reducing. The successful surface modification was verified by different membrane characterization techniques. The modified PDA/PEI-nAg CTA membrane exhibits enhanced hydrophilicity and improved antiadhesion and antimicrobial activity. Furthermore, the functional layer had an indistinctive effect on the membrane transport parameters. In addition, dynamic forward osmosis (FO) fouling experiment with raw municipal wastewater as feed solution indicated that the PDA/PEI-nAg CTA membrane exhibited notably lower water flux decrease compared to the nascent CTA membrane. The results of confocal laser scanning microscopy (CLSM) showed that PDA/PEI-nAg CTA membranes effectively reduced the adsorption of organic foulants (proteins and polysaccharides) and inhibited the formation and development of the fouling layer. The membrane surface modification of the CTA membrane with PDA/PEI and AgNPs efficiently mitigated membrane fouling in municipal wastewater treatment.

Three years of wastewater surveillance for new psychoactive substances from 16 countries

The proliferation of new psychoactive substances (NPS) over recent years has made their surveillance complex. The analysis of raw municipal influent wastewater can allow a broader insight into community consumption patterns of NPS. This study examines data from an international wastewater surveillance program that collected and analysed influent wastewater samples from up to 47 sites in 16 countries between 2019 and 2022. Influent wastewater samples were collected over the New Year period and analysed using validated liquid chromatography – mass spectrometry methods. Over the three years, a total of 18 NPS were found in at least one site. Synthetic cathinones were the most found class followed by phenethylamines and designer benzodiazepines. Furthermore, two ketamine analogues, one plant based NPS (mitragynine) and methiopropamine were also quantified across the three years. This work demonstrates that NPS are used across different continents and countries with the use of some more evident in particular regions. For example, mitragynine has highest mass loads in sites in the United States, while eutylone and 3-methylmethcathinone increased considerably in New Zealand and in several European countries, respectively. Moreover, 2F-deschloroketamine, an analogue of ketamine, has emerged more recently and could be quantified in several sites, including one in China, where it is considered as one of the drugs of most concern. Finally, some NPS were detected in specific regions during the initial sampling campaigns and spread to additional sites by the third campaign. Hence, wastewater surveillance can provide an insight into temporal and spatial trends of NPS use.

Performance evaluation of a diffusive hydrogel-based passive sampler for monitoring of polar organic compounds in wastewater

An upscaled passive sampler variant (diffusive hydrogel-based passive sampler; HPS) based on diffusive gradients in thin films for polar organic compounds (o-DGT) with seven times higher surface area (22.7 cm2) than a typical o-DGT sampler (3.14 cm2) was tested in several field studies. HPS performance was tested in situ within a calibration study in the treated effluent of a municipal wastewater treatment plant and in a verification study in the raw municipal wastewater influent. HPS sampled integratively for up to 14 days in the effluent, and 8 days in the influent. Sampling rates (Rs) were derived for 44 pharmaceuticals and personal care products, 3 perfluoroalkyl substances, 2 anticorrosives, and 21 pesticides and metabolites, ranging from 6 to 132 mL d−1. Robustness and repeatability of HPS deteriorated after exposures longer than 14 days due to microbial and physical damage of the diffusive agarose layer. In situ Rs values for the HPS can be applied to estimate the aqueous concentration of the calibrated polar organic compounds in wastewater within an uncertainty factor of four. When accepting this level of accuracy, the HPS can be applied for monitoring trends of organic micropollutants in wastewater.

Coupling high-rate activated sludge process with aerobic granular sludge process for sustainable municipal wastewater treatment

Achieving a neutral/positive energy balance without compromising discharge standards is one of the main goals of wastewater treatment plants (WWTPs) in terms of sustainability. Aerobic granular sludge (AGS) technology promises high treatment performance with low energy and footprint requirement. In this study, high-rate activated sludge (HRAS) process was coupled to AGS process as an energy-efficient pre-treatment option in order to increase energy recovery from municipal wastewater and decrease the particulate matter load of AGS process. Three different feeding strategies were applied throughout the study. AGS system was fed with raw municipal wastewater, with the effluent of HRAS process, and with the mixture of the effluent of HRAS process and raw municipal wastewater at Stage 1, Stage 2 and Stage 3, respectively. Total suspended solids (TSS), chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total phosphorus (TP) concentrations in the effluent were less than 10 mg/L, 60 mg/L, 0.4 mg/L, and 1.3 mg/L respectively at all stages. Fluctuations were observed in the denitrification performance due to changes in the influent COD/total nitrogen (TN) ratio. This study showed that coupling HRAS process with AGS process by feeding the AGS process with the mixture of HRAS process effluent and raw municipal wastewater could be an appropriate option for both increasing the energy recovery potential of WWTPs and enabling high effluent quality.

Enhanced nitrogen removal from municipal wastewater via a novel combined process driven by partial nitrification/anammox (PN/A) and partial denitrification/anammox (PD/A) with an ultra-low hydraulic retention time (HRT)

Anaerobic ammonia oxidation (Anammox) is a highly productive research area in municipal wastewater treatment. A novel combined process driven by partial nitrification/anammox (PN/A) and partial denitrification/anammox (PD/A) was established in this paper using a sequencing batch reactor (SBR) and two up-flow sludge beds (USBs). Municipal wastewater after carbon removal pretreatment in SBR entered PN/A-USB. PN/A process was initiated and enhanced by optimizing the intermittent aeration mode under low dissolved oxygen (DO). After enhancing and stabilizing the PD/A process, PN/A effluent entered the PD/A-USB along with raw municipal wastewater at a ratio of 4:1 and the combined system was established. Through this, this study achieved a nitrogen removal efficiency (NRE) of 84.9 % from municipal wastewater at an ultra-low total hydraulic residence time (HRT) of 3.9 h. Candidatus Brocadia (1.8 % in PN/A, 1.0 % in PD/A) was the only functional anammox bacterium in the combined process.

Assessment in treatment efficiency of a small-scale municipal wastewater treatment plant with activated sludge

Abstract In this paper, the treatment efficiency of a small-scale wastewater treatment plant (WWTP) with activated sludge was analysed in order to examine the impact of variations in the composition of incoming raw municipal wastewater. The characteristics of the wastewater were analysed with respect to COD, BOD5 and TSS values and loading during the two years, 2018 and 2019. The mixed liquid suspended solid (MLSS), sludge volume index (SVI), food to microorganism ratio (F/M), sludge age and hydraulic retention time (HRT) were used for evaluation of the performance of WWTP. Removal percentage is in the order of TSS &gt; BOD5 &gt; COD during 2018, while in 2019 is in the order BOD5 &gt; TSS &gt; COD. However, better values of removal efficiency for COD, BOD and TSS are obtained in 2019, which is connected to lower oscillation values of MLSS and SVI index. Biodegradability ratio of raw and treated wastewater, plant reliability factor (RF) and equivalent number of inhabitant (ENI) were determined. In addition, the economic cost of small-scale wastewater treatment plant (WWTP) with activated sludge was evaluated and discussed.

Modified bio-electrocoagulation system to treat the municipal wastewater for irrigation purposes

A modified biological-integrated electrocoagulation method was explored to treat municipal wastewater (MWW) for irrigation purposes. To use treated wastewater for irrigation purposes a wide range of contaminants removal was focused on in this study (turbidity, hardness, conductivity, TDS, TSS, chloride, Ammonia nitrogen, BOD, COD, and total coliform). Raw municipal wastewater (RMWW) was treated in a modified Bio-Electrocoagulation (BEC) cell. The cell was operated in a continuous flow mode and consisted of an electrocoagulation stage using aluminum (Al) electrodes followed by a bioremediation stage using a fixed bio-filter (BF), the design of the cell was further modified by the addition of a sand filter (SF). The effect of several parameters such as applied voltage (22, 26, and 30 V), inlet flow rate (1, 3, and 5 Lh-1), and initial pH (pH 3, 5, 7, 7.4, and 9) was investigated to determine the optimum operating conditions for selected responses. The most effective operating conditions for the BEC were investigated for the different irrigation water quality (WQ) indicators. It was observed that pH 7.4 and 26 V provide maximum removal efficiency of contaminants at the flow rate of 1 Lh-1. A fixed film BF plays a positive role to improve the degradation of contaminants after the EC unit up to 4% of NH3–N, 9.3% of BOD, and 7.8% of COD. In addition, using the SF improved the turbidity removal to 42.6%. The WQ specifications of the treated MWW using the BEC cell were compared with the standard specifications for restricted and unrestricted agricultural irrigation water. The overall operating cost of MWW treatment for irrigation purposes by using a modified bio-integrated electrocoagulation method was 0.76 $m−3.