Chemically Enhanced Primary Treatment Research Articles

Pilot-scale phosphorus recovery from biogas slurry to produce battery-grade FePO4: Chemical enhanced primary treatment coupled adsorption process

Recovering phosphorus (P) from wastewater was expected to bring win–win profits for environmental protection and clean energy industries. Ferric phosphate (FePO4) was a key raw material for lithium-ion battery production for new energy vehicles, which was a more valuable and promising product for recovering P from wastewater. There were challenges in recovering high-purity FePO4 from wastewater with complex components, especially in achieving large-scale recovery. Here, a pilot-scale platform, the Chemical Enhanced Primary Treatment (CEPT) coupled Fe@aminated-polyacrylonitrile (Fe-NH2-PAN) adsorption, was established for recovering battery-grade FePO4 from biogas slurry. The platform stably removed over 80% of PO43− from biogas slurry during long-term operation, the removed PO43− was enriched in chemical sludge and Fe-NH2-PAN, and then was leached into H2SO4 solution. FePO4 crystal was successfully recovered from the leaching solution (822.35 ± 15.91 mg/L PO43−) with a recovery rate of over 75%. Importantly, the lithium-ion battery prepared from recovered FePO4 exhibited excellent and stable electrochemical performance (with stable discharge specific capacity of 100.4–106.7 mAh/g at 1.0 C). This study provides a new path for large-scale P recovery in WWTPs.

Treatment of polluted river water using potential bioflocculant produced by Klebsiella pneumonia UKD24.

Chemically enhanced primary treatment (CEPT) is a rapid wastewater treatment process involving treating wastewater with two chemical-aided processes, coagulation, and flocculation. In the present study, a natural extracellular polymeric substance flocculant (EPSBF) produced by Klebsiella pneumonia UKD24, a bacterium isolated from the sewage treatment plant, and a synthetic polyacrylamide anionic polymer flocculant (PAM) were evaluated to treat polluted river water. The synthetic PAM showed immediate turbidity reduction after agitation, while the EPSBF expressed a rapid decrease in optical density. After 20 min of the settling period, the EPSBF showed reduced rates of turbidity, optical density, and chemical oxygen demand at 74.14 ± 5.2%, 89.37 ± 0.76%, and 87.21 ± 0.73%, respectively, while PAM showed 67.08 ± 4%, 85.68 ± 2%, and 86.57 ± 2%, respectively. EPSBF treatment significantly improved the water quality parameters in terms of total dissolved solids, total suspended solids, conductivity, and oxidation-reduction potential than PAM treatment. However, the EPSBF has shown a more water-holding capacity and relatively weak flock formation, producing more sludge volume than PAM. Furthermore, though the sludge produced by the EPSBF treatment had a higher moisture content, it showed shorter capillary suction time (CST). In contrast, sludge formed in PAM treatment had lower moisture content, but it exhibited prolonged CST value indicating that PAM treatment sludge showed slow dewaterability.

Direct application of chemically enhanced primary treatment in a municipal wastewater treatment plant: A case study

A feasible and efficient implementation of an Fe-based chemically enhanced primary treatment (CEPT) in a large conventional wastewater treatment plant (WWTP) was thoroughly evaluated. The influence of the velocity gradient and hydraulic retention time in the coagulation and flocculation stages, as well as the coagulant (FeCl3) dosage, were evaluated at lab-scale. Standard Jar Tests were performed to simulate CEPT, and the results were compared with those obtained by primary settling without coagulant. The increase in FeCl3 dosage and flocculation hydraulic retention time (HRTF) increased the primary settling COD removal capacity between 6.6% and 18.1%, highlighting its effect on the easily biodegradable COD fraction. The COD removal capacity increased up to 16.8% when working with an HRTF of less than 4 min, facilitating CEPT direct application in conventional WWTPs, avoiding the need to incorporate flocculation chamber, with a corresponding decrease in the associated implementation cost. The presence of residual Fe in the primary settling effluent and an increase in the primary sludge volume were the main drawbacks of the process. The coagulation and flocculation velocity gradients or the coagulation hydraulic retention time did not significantly influence the process.

Effect of FeCl3 concentration in chemically enhanced primary treatment on the performance of a conventional wastewater treatment plant. A case study

The effect of coagulant dosage in a chemically enhanced primary treatment (CEPT) on the performance of a conventional wastewater treatment plant (WWTP) has been investigated. Lab-scale experiments simulations were carried out in order to evaluate the effect of coagulant addition on the primary settling performance. In these experiments, FeCl3 was used as coagulant. Later, the WWTP was theoretically simulated using a commercial software (WEST®) to evaluate the effect of coagulation/flocculation on the global system, based on the results obtained at lab-scale. According to these results, the CEPT modifies the organic matter balance in the WWTP, decreasing the contribution of readily (SS) and slowly (XS) biodegradable fractions of COD to the aerobic biological process up to 27.3% and 80.8%, respectively, for a dosage of FeCl3 of 24 mg L−1. Consequently, total suspended solids in the aerobic reactor and the secondary purged sludge decreased up to 33% and 13%, respectively. However, the influence on effluent quality was negligible. On the contrary, suspended solids concentration in the sludge to be treated by anaerobic digestion increased, mainly regarding the Ss and Xs fractions, which caused an 8.1% increase in biogas production potential, with approximately 60% of CH4 concentration.

Efficient treatment of leather wastewater using a combination of CEPT and SBR with a novel flocculant

The suspended solids in leather wastewater serve as carriers for many pollutants, and traditional treatment methods have certain limitations. Hence, this research integrated chemically enhanced primary treatment (CEPT) with sequential batch reactor (SBR) technologies by using ecologically friendly vermiculite flocculants instead of conventional ones. In the CEPT phase, with solely addition of the vermiculite flocculant, the removal rates for turbidity, chemical oxygen demand (COD), suspended solids (SS), and total phosphorus (TP) reached 97.9 %, 62.1 %, 94.5 %, and 88.6 %, respectively. Upon adding both the vermiculite flocculant and a coagulant aid, the removal ratios improved to 98.9 %, 75.1 %, 97.6 %, and 88.6 %. Processing after SBR biochemical treatment further enhanced the removal ratios to 99.9 %, 96.7 %, 99.9 %, and 95.5 % for turbidity, COD, SS, and TP, respectively. Additionally, the high-throughput sequencing revealed a dynamic change in the dominant microbial phyla throughout the treatment process, which is associated with the effectiveness of treating COD, TP, and TN. In summary, the use of the vermiculite flocculant combined with the CEPT+SBR approach demonstrates significant ecological and environmental advantages in treating leather wastewater, providing valuable insights for future treatment strategies.

Applicability of hybrid treatment to reduce the footprint of domestic and industrial wastewater of developing countries

Wastewater pollution is a serious concern, especially in developing countries such as Pakistan. The untreated domestic and industrial wastewater is typically discharged into sewers, natural drains, or water bodies. There is a dire need to evaluate the applicability of low-cost treatment technologies. Hybrid wastewater treatment (HWWT), comprising of chemically enhanced primary treatment (CEPT) and intermittent sand filter (ISF), was adopted to treat domestic, process and manufacturing, and food industry wastewaters. The wastewater pollution and contamination were assessed in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS). The removal efficiency (RE) performance of HWWT was compared with the CEPT system only. Considering the CEPT only, the RE of BOD was ≈70 % for domestic, >80 % for process and manufacturing, and ≈50 % for the food industry. For COD, the RE was high in process & manufacturing (RE ≈ 81 %), followed by food (RE ≈ 55 %) and domestic wastewater (RE ≈ 17 %). Furthermore, the CEPT provided >95 % TSS removal in all wastewater types. The HWWT increased TSS removal by ≈2 %, BOD removal by ≈13 %, and COD removal by ≈27 % compared to the CEPT system. Therefore, HWWT proved more efficient in treating both domestic and industrial wastewater. The HWWT reduced the greywater footprint (GWF) by 50–60 % when compared to the CEPT system. This study provided knowledge of the characteristics of domestic and industrial wastewater. Furthermore, provides a basis to assess the applicability and performance of various wastewater treatment systems under given settings.

A State-of-The-Art Technical Review on Chemically Enhanced Primary Treatment Plant

This review paper aims to provide a comprehensive assessment of chemically enhanced primary treatment (CEPT) processes in wastewater treatment plants (WWTPs). The outdated and ineffective performance of existing treatment plants has raised concerns regarding public health and environmental safety. CEPT has emerged as a promising alternative approach to enhance the efficiency and effectiveness of primary treatment. By adding chemical coagulants or precipitants to the wastewater, CEPT facilitates the aggregation and settling of suspended solids and contaminants, leading to improved treatment outcomes. This review evaluates the performance and effectiveness of different chemical coagulants, including ferric chloride (FeCl3), polyaluminum chloride (PACl), and alum, in terms of their ability to remove various pollutants such as suspended solids, turbidity, organic matter, nutrients, and emerging contaminants.
 The findings from the reviewed studies indicate that different coagulants exhibit varying efficiencies in removing specific parameters such as turbidity, total suspended solids (TSS), chemical oxygen demand (COD), and phosphorous. Alum, ferric chloride, and ferric sulfate showed effectiveness in tannery wastewater treatment, while PACl maximized the removal of macro pollutants. The use of organic carbon sources and sludge recycling demonstrated cost reductions and improved nutrient removal. CEPT was found to be effective in TSS and BOD removal, potentially allowing for compact treatment facilities and enhancing the capacity of biological treatment units. The utilization of recovered alum from water treatment sludge (WTS) in CEPT showed comparable efficiencies to fresh alum. The paper also identifies research gaps and future directions in the field of chemically enhanced primary treatment, while discussing the challenges and limitations associated with CEPT processes. While the reviewed studies provide valuable insights into the performance of different coagulants and coagulant aids, further research is necessary to assess their long-term effects and cost-effectiveness in large-scale applications. The optimal choice of coagulant depends on specific wastewater characteristics and treatment goals. Understanding and optimizing CEPT processes will contribute to the development of innovative solutions for challenges in wastewater treatment systems caused by urbanization, population growth, and emerging contaminants in the major city like Kathmandu.

Coupling ozonation with hydrogen peroxide and chemically enhanced primary treatment for advanced treatment of grey water

Grey water is a valuable water source due to its high-volume generation. This study was conducted with grey water that was obtained from a hotel with 1000 inhabitants and average flowrate of 40 m3/day. The main objective of the study was to determine the optimum operational conditions for ozonation process in terms of micropollutant removal along with conventional parameters and to enhance the removal efficiency of ozonation process by coupling with hydrogen peroxide or chemically enhanced primary treatment (CEPT) process. The results indicated that the COD removal efficiencies were around 37% by both sole ozonation and peroxone processes. However, CEPT+ozonation process increased the COD removal efficiency to 71%. On the other hand, TSS removal efficiency by peroxone and CEPT+ozonation processes were 57% and 89%, while TP removal efficiencies were 26% and 74%, respectively. All micropollutants that were detected in grey water, were removed until the limit of detection (LOQ) with all treatment processes. Overall evaluation of the results indicated that CEPT combined with the ozonation process was more effective in terms of removal of conventional parameters compared to sole ozonation and peroxone processes. Therefore, CEPT+ozonation process with the optimum ozone dosage and contact time is recommended to increase the possibility to reuse the treated grey water. A feasibility analysis was conducted for optimum ozonation mode and CEPT+ozonation, and the results revealed that unit total cost and unit operational cost for ozonation system was 0.027 $/m3 and 0.01 $/m3, respectively. The unit operational cost for CEPT+ozonation system was 0.124 $/m3.

Impact of primary treatment methods on sludge characteristics and digestibility, and wastewater treatment plant-wide economics

Biogas production from anaerobic sludge digestion plays a central role for wastewater treatment plants to become more energy-efficient or even energy-neutral. Dedicated configurations have been developed to maximize the diversion of soluble and suspended organic matter to sludge streams for energy production through anaerobic digestion, such as A-stage treatment or chemically enhanced primary treatment (CEPT) instead of primary clarifiers. Still, it remains to be investigated to what extent these different treatment steps affect the sludge characteristics and digestibility, which may also impact the economic feasibility of the integrated systems. In this study, a detailed characterization has been performed for sludge obtained from primary clarification (primary sludge), A-stage treatment (A-sludge) and CEPT. The characteristics of all sludges differed significantly from each other. The organic compounds in primary sludge consisted mainly of 40% of carbohydrates, 23% of lipids, and 21% of proteins. A-sludge was characterized by a high amount of proteins (40%) and a moderate amount of carbohydrates (23%), and lipids (16%), while in CEPT sludge, organic compounds were mainly 26% of proteins, 18% of carbohydrates, 18% of lignin, and 12% of lipids. The highest methane yield was obtained from anaerobic digestion of primary sludge (347 ± 16 mL CH4/g VS) and A-sludge (333 ± 6 mL CH4/g VS), while it was lower for CEPT sludge (245 ± 5 mL CH4/g VS). Furthermore, an economic evaluation has been carried out for the three systems, considering energy consumption and recovery, as well as effluent quality and chemical costs. Energy consumption of A-stage was the highest among the three configurations due to aeration energy demand, while CEPT had the highest operational costs due to chemical use. Energy surplus was the highest by the use of CEPT, resulting from the highest fraction of recovered organic matter. By considering the effluent quality of the three systems, CEPT had the highest benefits, followed by A-stage. Integration of CEPT or A-stage, instead of primary clarification in existing wastewater treatment plants, would potentially improve the effluent quality and energy recovery.

Toward Energy Neutrality: Novel Wastewater Treatment Incorporating Acidophilic Ammonia Oxidation.

Chemically enhanced primary treatment (CEPT) followed by partial nitritation and anammox (PN/A) and anaerobic digestion (AD) is a promising roadmap to achieve energy-neutral wastewater treatment. However, the acidification of wastewater caused by ferric hydrolysis in CEPT and how to achieve stable suppression of nitrite-oxidizing bacteria (NOB) in PN/A challenge this paradigm in practice. This study proposes a novel wastewater treatment scheme to overcome these challenges. Results showed that, by dosing FeCl3 at 50 mg Fe/L, the CEPT process removed 61.8% of COD and 90.1% of phosphate and reduced the alkalinity as well. Feeding by low alkalinity wastewater, stable nitrite accumulation was achieved in an aerobic reactor operated at pH 4.35 aided by a novel acid-tolerant ammonium-oxidizing bacteria (AOB), namely, Candidatus Nitrosoglobus. After polishing in a following anoxic reactor (anammox), a satisfactory effluent, containing COD at 41.9 ± 11.2 mg/L, total nitrogen at 5.1 ± 1.8 mg N/L, and phosphate at 0.3 ± 0.2 mg P/L, was achieved. Moreover, the stable performances of this integration were well maintained at an operating temperature of 12 °C, and 10 investigated micropollutants were removed from the wastewater. An energy balance assessment indicated that the integrated system could achieve energy self-sufficiency in domestic wastewater treatment.

Photo-Fenton and Electro-Fenton performance for the removal of pharmaceutical compounds in real urban wastewater

The objective of this study was to evaluate the performance of Photo-Fenton (PF) and Electro-Fenton (EF) processes and find the best option for the removal of pharmaceutical compounds in a real urban effluent of wastewater treated by a chemically-enhanced primary treatment (CEPT). In both processes was used the iron residual (average 2.4 mg L−1) resulting from CEPT avoiding further iron salts addition. Central composite designs (CCD) with response surface methodology (RSM) were applied to select the operational conditions. Humic acid (HA) was the chelating agent in the PF process, where Fe3+:HA molar ratios and H2O2 concentrations were the factors. While current density and the electrolysis time were the factors in the EF process. The operational conditions selected for evaluating the removal of pharmaceutical compounds were a 1:6.8 for Fe3+:HA molar ratio and 100 mg L−1 for H2O2 in PF, and 80 mA cm−2 and 100 min for EF. EF was evaluated with a Boron Doped Diamond electrode anode and cathode (BDD/BDD cell) without the addition of supporting electrolyte. In PF, the removal efficiencies were between 24.2% and 56% for gabapentin, ibuprofen, naproxen, pentoxifylline, and venlafaxine. Compounds such as carbamazepine and fenofibric acid increased their concentration after the PF process. This increase was related to the enzymatic cleavage of glucuronides and the possible presence of •OH radical scavengers that decreased the process efficiency. By contrast, EF showed an average removal efficiency of between 53.3% and 99.9% for all identified compounds, resulting in the best option for treating this real effluent of wastewater. These results in EF could be related to a synergic effect between homogeneous •OH and BDD(•OH) that contributed to improving the oxidation of the contaminants. The electrical energy per order (EEO) was determined with values between 11.5 and 144.9 kWh log−1 m−3, suggesting a need to apply other preliminary treatments that reduce the current density (i.e., coupled treatments with the biological process).

A comparative study on polyaluminum chloride (PACl) and Moringa oleifera (MO) chemically enhanced primary treatment (CEPT) in enhanced biogas production: anaerobic digestion performance and the Gompertz model.

A comparative study was performed to estimate biogas production from sludge produced by organic and inorganic chemically enhanced primary treatments (CEPTs). To this end, the effects of two coagulants, polyaluminum chloride (PACl) and Moringa oleifera (MO), on CEPT and biogas production in anaerobic digestion were surveyed within an incubation period of 24 days. The optimal dosage and pH of PACl and MO were optimized in terms of sCOD, TSS and VS parameters in the CEPT process. Next, the digestion performance of anaerobic digestion reactors fed with sludge obtained from PACl and MO coagulants at a batch mesophilic reactor (37 ± 1 °C) was surveyed from the biogas production, volatile solid reduction (VSR) and Gompertz model. At the optimal conditions (pH = 7 and dosage = 5 mg L-1), the removal efficiency of COD, TSS and VS in CEPT assisted with PACL was 63, 81 and 56%, respectively. Moreover, CEPT assisted with MO led to the removal efficiency of COD, TSS and VS until 55, 68 and 25%, respectively. The highest methane yield (0.598 L gVS removed-1) was obtained in an anaerobic digestion reactor with sludge from the MO coagulant. The anaerobic digestion of CEPT sludge instead of primary sludge resulted in higher sCOD removal efficiency, and 43-50% of sCOD was observed compared with the removal of 32% for the primary sludge. Furthermore, the high coefficient of determination (R2) demonstrated the trustworthy predictive precision of the modified Gompertz model with actual data. The combination of CEPT and anaerobic digestion, especially using natural coagulants, provides a cost-effective and practical way to increase BMP from primary sludge.

Occurrence and stability of PCMX in water environments and its removal by municipal wastewater treatment processes

Para-chloro-meta-xylenol (PCMX) is a synthetic antiseptic used extensively to control the spread of germs and viruses, and as a result, enormous amount of PCMX could be discharged to water environments through drainage. To investigate the extent of PCMX contamination, water samples were collected from rivers and coastal waters in Hong Kong, and PCMX concentrations were determined by a newly developed method using liquid chromatography-tandem mass spectrometry combined with stable isotope-dilution. We discovered widespread PCMX pollution in the water environment. Then, we revealed for the first time that PCMX in wastewater is not effectively removed by chemically enhanced primary treatment (CEPT), one of the wastewater treatment processes used in Hong Kong (∼75% of wastewater) and other megacities around the world. This suggests that the CEPT effluent or the primary treatment effluent is an unintended continuous source of pollution for PCMX in water environments. Finally, we found that PCMX was relatively stable in the water environment and could pose a risk to aquatic organisms. These findings underscore the importance of raising public awareness of the environmental consequences from overuse of PCMX-based disinfectants and the need to reevaluate the various wastewater treatment processes in removing PCMX.

Fouling reduction in nanofiltration membranes in the treatment of municipal sewage - effect of coagulant type used for prior chemically enhanced primary treatment.

The limiting factor in wide-scale application of membranes for wastewater treatment is membrane fouling. Coagulation has emerged as an effective technique for fouling control. In this research, municipal wastewater was treated using a two-stage treatment. In stage-1, chemically enhanced primary treatment (CEPT) was rendered using an optimum dose of two coagulants, i.e. alum, ferric chloride and a 1:1 mix of both. The optimum doses for coagulants were determined using ajar test. In stage-2, a nanofiltration (NF) membrane was used to further treat the effluent from stage-1. In CEPT, the 1:1 mixture of coagulants showed maximum removals, i.e. 75-77% for the total suspended solids and 73-75% for the chemical oxygen demand (COD). Stage-2 provided 85-95% removals for turbidity (0.88 nephelometric turbidity units), COD (41 mg/L), total dissolved solids (101 mg/L), hardness (11 mg/L as CaCO3), chlorides (80 mg/L), and heavy metals (copper [0.03 mg/L] and lead [0.02 mg/L]). The operational time of the NF membrane was 46 min, 55 min and 70 min using alum, ferric chloride, and mix (1:1), respectively. Significant reduction was observed in membrane fouling for 1:1 mixture of coagulants. The effluent met the US Environmental Protection Agency guidelines for non-potable reuse.

MABR process development downstream of a carbon redirection unit: opportunities and challenges in nitrogen removal processes

ABSTRACT Carbon redirection has become the desired option for sustainable and energy-efficient wastewater treatment due to its contribution to a circular economy. However, its impact on downstream processes such as nitrification and denitrification requires further investigation. This research characterizes the nitrogen removal performance, footprint, aeration mode, and microbial composition of a flow-through membrane aerated biofilm reactor (MABR) downstream of a chemically enhanced primary treatment (CEPT) carbon redirection unit. The batch and long-term studies demonstrated relatively higher nitrification rates than those reported using conventional primary treated wastewaters. The results indicated that reducing carbon in the liquid train positively impacted nitrification by achieving 87 ± 12% (1.4 ± 0.4 g/m2.d) ammonia removal with an effluent 2.5 ± 2.8 mg/L ammonia concentration at a short hydraulic retention time (HRT) of 2.5 h. Despite the lower (1.9 ± 1) soluble COD:N, up to 75 ± 25% (0.6 ± 0.4 g/m2.d) total nitrogen removal was achieved at 4 h HRT by implementing intermittent aeration. The batch tests using the developed biofilms showed nitrification (denitrification) capacity up to 11 ± 1.7 gNH4-N/m2.d (8.5 ± 0.5 gNO3-N/m2.d) and 2.7 ± 0.6 gNH4-N/m2.d (2 ± 0.3 gNO3-N/m2.d) corresponding to ammonia and nitrate concentrations ranging from 10–30 mg/L and 2–10 mg/L, respectively. Microbial analysis indicated that the nitrifiers such as Nitrosomonas and Nitrospira were the dominant species. The ammonia-oxidizing, nitrite-oxidizing, and denitrifying bacteria relative abundances were 10.3 ± 1.5%, 20.7 ± 1.7%, and 20.0 ± 2.8% under continuous aeration and 1.3 ± 0.07%, 1.8 ± 0.09%, and 40.5 ± 3.1% under intermittent aeration, supporting the observed ammonia and total nitrogen removal processes, respectively. Overall, the results demonstrated that MABR downstream of the CEPT behave differently; thus, design guides should be updated accordingly.

Chemically enhanced primary treatment, microsieving, direct membrane filtration and GAC filtration of municipal wastewater: a pilot-scale study

ABSTRACT Chemically enhanced primary treatment (CEPT) followed by microsieving and direct membrane filtration (DMF) as ultrafiltration, was evaluated on pilot scale at a municipal wastewater treatment plant. In addition, a granular activated carbon (GAC) filter downstream of DMF was evaluated for the removal of organic micropollutants. Up to 80% of the total organic carbon (TOC) and 96% of the total phosphorus were removed by CEPT with microsieving. The additional contribution of subsequent DMF was minor, and only five days of downstream GAC filtration was possible due to fouling of the membrane. Of the 21 organic micropollutants analysed, all were removed (≥ 98%) by the GAC filter until 440 bed volumes, while CEPT with microsieving and DMF removed only a few compounds. Measurements of the oxygen uptake rate indicated that the required aeration for supplementary biological treatment downstream of CEPT with microsieving, both with and without subsequent DMF, was 20−25% of that in the influent wastewater. This study demonstrated the potential of using compact physicochemical processes to treat municipal wastewater, including the removal of organic micropollutants.

Enhanced primary treatment for net energy production from sewage – The genetic clarification of substrate-acetate-methane pathway in anaerobic digestion

• Substrate-acetate-methane pathway in AD fed with CEPT sewage sludge was elucidated. • Net energy increased from −0.36 kWh to 0.06 kWh per m 3 sewage treated. • Total COD degradation achieved with 7.44 g/day with methane yield at 0.42 m 3 /kg VSS in . • Bio-analysis confirmed high cellulolytic bacteria/methanogens and low syntrophs. • Cellulosome related genes were identified in a methanogen Methanosarcina . Organic matters such as cellulose are key components in municipal sewage, and its degradation consume significant aeration energy in biological process. Pre-harvesting organic particles by chemical enhanced primary treatment (CEPT) could prevent energy consumption while increase bioenergy potential in anaerobic digestion (AD). This study provides biological proof of an “substrate-acetate-methane pathway” that may result in energy positive practice in sewage treatment. When applying CEPT sludge in AD, a stable methane yield at 0.42 m 3 /kg VSS in was achieved. Meanwhile, the results of mass balance suggested that for biogas conversion of CEPT sewage sludge, cellulose and protein degradation played a key factor at low organic loading operation (2 gVSS/L-day, SRT = 15 days), while lipid degradation was more significant at high loading operation (3 gVSS/L-day, SRT = 20 days). Microbial analysis revealed high abundance of cellulolytic bacteria, cellulosome related genes, and methanogens; and low abundance of syntrophs, suggesting effective degradation and uptake of amorphous cellulose to acetate. An unexpected result showed that cellulosome genes were identified from two high abundance species of Methanosarcina . In line with the reduced total volatile fatty acids and propionate (to 1,200 and 600 mg/L, respectively), such cellulolytic and methanogenic synergy implies unique syntrophs bypass for bioenergy production. With the combination of CEPT sludge and AD, the net energy of sewage treatment could increase from −0.36 kWh to 0.06 kWh per cubic meter wastewater treated, including reduced energy consumption in aeration process.

Capturing organics from municipal wastewater using a primary sludge-derived polymer

Among the numerous organics capture technologies, chemical enhanced primary treatment (CEPT) offers several distinct advantages, including low energy consumption, less oxidation of organic matter, and large-scale operation. However, CEPT currently relies heavily on metal salt-based coagulants, which have some limitations in terms of agent costs, sludge volume, and alkalinity variation. This preliminary study proposes the use of organic matter from municipal wastewater as raw materials (i.e., primary sludge) for the preparation of organic polymer, which would be used in place of conventional inorganic coagulants for organics recovery. An organic flocculant (PSBs-g-PAM-co-PDMC) was prepared by grafting DMC [(2-methacryloyloxyethyl) trimethyl ammonium chloride] and AM (acrylamide) onto the backbone of primary sludge-derived biopolymers (PSBs), which formed during the of sludge hydrothermal treatment. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential analysis, and gel permeation chromatography were used to characterize the chemical properties of PSBs-g-PAM-co-PDMC. These methods confirmed the incorporation of AM and DMC into the PSBs' backbone. PSBs-g-PAM-co-PDMC was used to investigate the COD (chemical oxygen demand) capture characteristics of real municipal wastewater. The results indicated that by dosing 30 mg/L PSBs-g-PAM-co-PDMC, approximately 60.0% of the COD was removed. At a low dosage (≤10 mg/L), COD can be efficiently reduced by removing predominantly particulate COD, while at a higher dosage, the further decrease of COD depends on the removal of colloidal COD. Both increasing and decreasing the pH have an effect on the COD removal mechanism. Additionally, the effluent quality and production cost were analyzed.

Feasibility Study on Wastewater Treatment Using Chemically Enhanced Primary Treatment

A techno-economic analysis was performed to investigate wastewater treatment feasibility using chemically enhanced primary treatment (CEPT) compared to conventional primary treatment (PT). An experimental study was conducted to investigate the performance of CEPT at optimum conditions, and experimental results were used to feed the techno-economical study with required input data. The wastewater treatment was focused on reducing BOD5, COD, and TSS. The comparison between CEPT and PT was concerned with removal efficiency and process economics. CEPT process has shown better efficiency compared to PT process. The experimental work indicated that ferric chloride is the optimum coagulant agent since it is highly efficient and available at a low cost. The optimum coagulant experimental results showed that the turbidity removal efficiency was 82%, COD removal 84%, BOD removal 68.1%, and SS removal 85%. The techno-economic study was performed to investigate the feasibility of CEPT. The techno-economic evaluation indicated that CEPT is a cost-effective and technically viable process for wastewater treatment. The techno-economic evaluation indicated that CEPT is a cost-effective and technically viable process for wastewater treatment as the operating cost can be reduced by 66% compared to PT.

Biorefinery potential of chemically enhanced primary treatment sewage sludge to representative value-added chemicals - A de novo angle for wastewater treatment

Chemically enhanced primary treatment (CEPT) is an emerging sewage treatment strategy due to its high efficiency and small land requirement. CEPT sludge can be easily dewatered and used for energy recovery through incineration. However, with large amount of reusable nutrients (40% organic carbon, 23% lipids, and 17% protein), the value of CEPT sludge may have been underestimated. In this study, the biorefinery potential of CEPT sludge has been proven via production of 28.9 g/L ethanol or 50.3 g/L lactic acid (LA) or 1.43 filter paper unit (FPU)/mL cellulase from 10 g of CEPT sludge experiment. Inhibition on cell growth and potential inhibitors from plasticizers, pharmaceuticals, and surfactants were determined. Nevertheless, production titer was not affected or performed even better than the non-inhibitors controls. CEPT sludge showed significant potential in biochemical conversion, and the related products may offer an opportunity to support wastewater treatment toward sustainability and carbon neutrality.