Recycling Of Sludge Research Articles

Responses of Freshwater Invertebrates to Imhoff Tank Sewage Effluents: A Preliminary Study in Four Watercourses with Different Ecological Status (Abruzzo, Central Italy)

In many EU countries, a large proportion of domestic effluents is treated in small, decentralized wastewater treatment plants (WWTPs) which often lack appropriate treatment technologies. The low efficiency of these systems and their incorrect maintenance often contribute to environmental deterioration, with a large quantity of inadequately treated sewage dispersed in the soil or discharged into superficial watercourses. In the Abruzzo region (Central Italy), almost all rivers and streams receive wastewater from Imhoff tanks with only primary treatments. The ecological impacts of these effluents have rarely been investigated. This paper aimed to evaluate the response of freshwater invertebrates to Imhoff effluents in receiving watercourses with different ecological status. Our results showed that wastewater from Imhoff plants negatively affected the structure and composition of freshwater communities, with a reduction in the richness and abundance of more sensitive taxa and an increase in the most tolerant ones. These negative effects were more accentuated during low flow periods and in streams with moderate ecological status. To improve the ecological status of rivers and streams and to limit the diffusion of pathogens and micropollutants in freshwater, a more efficient (secondary treatments, possibly with nature-based solutions) and sustainable (water reuse or sewage sludge recycling) approach to wastewater treatment in decentralized WWTPs is urgently needed.

Multi-Source Ferrous Metallurgical Dust and Sludge Recycling: Present Situation and Future Prospects

Multi-Source Ferrous Metallurgical Dust and Sludge Recycling: Present Situation and Future Prospects

Recycling of granite sludge for the preparation of high‐strength glazed glass‐ceramics using stepwise sintering

AbstractThe reutilization of granite sludge generated in granite cutting and processing possesses economic and ecological benefits. In this study, high‐strength glazed glass‐ceramics were prepared entirely from granite powder using dense sintering and instantaneous glaze firing. The densification and glaze formation are clarified in terms of phase evolution to study their effects on the flexural strength and surface glossiness of the glass‐ceramics. The milling process promotes particle refinement and the removal of colored minerals, thus increasing the powder whiteness and sinterability. After dense sintering at 1100°C, instantaneous glaze firing at high temperatures decreases the flexural strength while greatly increases the surface glossiness of the glass‐ceramics due to the dissolution of quartz and feldspars in the liquid phase. After the acid‐leached powder was densely sintered and fired with a rapid heating of 50°C/min to 1300°C, the pinhole‐free glazed glass‐ceramic has a flexural strength of 112.5 MPa and a surface glossiness of 54.7 GU (glossiness unit), meeting the quality requirements of the bright glazed tiles in the market. The stepwise sintering process provides a simple processing route for recycling granite sludge into decorative construction tiles and high‐temperature glazes, promising the scalable and value‐added utilization of granite sludge.

Recycling waste dredged sludge into bifunctional coating for one-step separation of multitasking dye contaminated oil/water emulsions

Effective strategies for disposing of waste dredged sludge (WDS) and separating multitasking oil/water emulsions in one way are in urgently demand but still insufficient. Herein, a bifunctional waste dredged sludge-coated polyvinylidene fluoride membrane (WDS-PVDF membrane) was prepared via vacuum filtration for one-step separation of emulsified oil and water-soluble dye. Compared with traditional membranes, WDS-PVDF membrane has advantages in the selected green solvent, low-cost raw materials, and facile fabrication process. Without chemical modification, hierarchical roughness and unique chemical composition endowed the membrane extraordinary underwater superoleophobicity and anti-oil-fouling performance. Significantly, the membrane could separate emulsified oil and water-soluble dye in one step with high separation efficiency (for emulsified oil: > 99.3 %, and for methylene blue: > 99.5 %). Therefore, this work not only offers an effective strategy for large-scale recycling and reutilization of waste sludge, but also for practical complex oily wastewater treatment.

Sustainable treatment and recycling of oily sludge: Incorporation into gel -system to improve oil recovery.

Oily sludge is very difficult to treat in solid waste, how to achieve on-site treatment and recycling of the sludge is rarely reported. This research proposes a new treatment method for oily sludge by adding the oily sludge into the gel water plugging system designed for low-performing oilfields-sludge re-injection technology. The gel system of oily sludge can resist dehydration for 150 days at a high temperature up to 140 °C and a salinity of 2.11 × 105 mg/L, and its strength reaches grade I. The microstructure of the gel was revealed using scanning electron microscopy (SEM). The addition of oily sludge made the gel system microstructure develop a dense three-dimensional network structure, which can effectively improve the strength and temperature resistance of the gel system. Differential scanning calorimetry (DSC) experiments show that the gel with oily sludge can maintain temperature resistance even at 188 °C. Laboratory displacement experiments show that the breakthrough pressure of the gel system can reach 3418 kPa/m, and the plugging rate is above 98%. The performance of the system was improved by adding oily sludge into the gel as an enhancer, which provided a research idea for harmless treatment, resource utilization and clean production of oily sludge.

Enhanced the plant germination in sandy soil by novel sludge-based biochar prepared with residual sludge after EPS extraction as soil amendment

The preparation of novel sludge-based biochar and its application as soil amendments are considered as an environmentally friendly way to realize sludge recycling. In this study, a novel sludge-based biochar (RBC) was prepared by residual sludge after extracellular polymers (EPS) extraction, and the effect of RBC as soil amendment on the ryegrass germination in sandy soil was explored. The results indicated that the biochar yield by residual sludge after EPS extraction was higher than that by raw sludge. Compared with the raw sludge-based biochar (SBC), a variety of new functional groups and crystalline structures were formed in RBC, and the specific surface area and pore volume were significantly increased. Furthermore, a largest NH4+-N adsorption capacity of 7.6 mg/g was achieved by HNO3 modified RBC (MRBC) under an optimum pH of 7. Moreover, the ryegrass germination rate and ryegrass height were increased by 52.0 % and 213.4 % in sandy soil with MRBC adsorbed with NH4+-N as soil amendment compared with that in sandy soil with SBC addition. Accordingly, RBC has great potential for the preparation of novel sludge-based biochar and plays a prominent role as a soil amendment in enhancing plant growth in sandy soil. The above research will provide a new direction for the advanced resource utilization of sewage sludge.

A two-step approach of ozonation pre-oxidation and re-flocculation to regulate drinking water treatment sludge: Sludge reflux and enhanced coagulation

The characteristics of drinking water treatment sludge (DWTS) are important factors limiting the coagulation effect after sludge recycling. To enhance the coagulation performance of DWTS recycling, a two-step pretreatment strategy was employed, including ozonation pre-oxidation and the re-flocculation of polymeric aluminum chloride (PACl) and polyacrylamide (PAM). Ozonation pre-oxidation transformed insoluble organic matter into dissolved organic matter (DOM), reducing the organic content by 12.58% for UV254 and 8.94% for dissolved organic carbon (DOC) in the DWTS recycling process. Following re-flocculation with PACl and PAM, the size, zeta potential, and settling velocity of the ozonated sludge were further increased from 30.27 μm, −12.57 mV, and 2.06 mm/s to 187.6 μm, −3.49 mV, and 6.42 mm/s, respectively, which exhibited higher turbidity removal in DWTS recycling process. Following the two-step method, larger, denser, and more reversible flocs were observed during the recycling process, and the settling efficiency of the flocs was enhanced, which enabled achieving better water quality in a shorter duration. These findings provide innovative insights into drinking water plant optimization and sludge management.

Co-pretreatment (calcium peroxide + freeze) to improve anaerobic fermentation of waste activated sludge: Method optimization and mechanism insights

The reduction, harmlessness, and recycling of waste-activated sludge (WAS) can be accomplished by anaerobic fermentation, where sludge disintegration is the key speed-limiting process. Co-pretreatment, as a derivative of pretreatment, has attracted more and more attention. However, obtaining optimal co-pretreatment conditions is difficult. Response surface methodology (RSM) can combine statistical analysis with mathematics to optimize the parameters. Therefore, in the current work, RSM optimization for CaO2-freezing co-pretreatment conditions to improve the production of short-chain fatty acids (SCFAs) from WAS was carried out using the Box-Behnken Design based on Design Expert software. We obtained the optimal values of three pretreatment parameters: −18 °C freezing temperature, 48.6 h freezing time, and 0.19 g CaO2/g VSS addition. After 5 days of fermentation, the maximum cumulative yield of SCFAs was 162.34 mg COD/g VSS. CaO2-freezing co-pretreatment promoted the solubilization and release of organic matter in WAS during anaerobic fermentation, which not only provided more organic matter for the subsequent production of SCFAs but also improved the methane production capacity in the anaerobic digestion stage. 16S rRNA genes sequencing revealed that the abundance of SCFAs-producing bacteria (i.e., Macellibacteroides and Proteiniclasticum) was significantly enriched in the fermentation tank after CaO2-freezing co-pretreatment. All in all, this study successfully optimized the co-pretreatment conditions based on RSM, providing new insights and effective solutions for the environmentally friendly and efficient realization of solid waste recycling.

Persulfate catalyst synthesized with waterworks sludge for degrading Safranine T in the presence of boron

ABSTRACT Energy conservation and emission reduction are the general trend of the present world. In this study, a catalyst of 3WSH based on the waste recycle of waterworks sludge (WS) and Chinese herbs was prepared using one-step calcination treatment and then characterized by SEM, XRD, XPS, FTIR and BET. The catalytic performance of 3WSHB for activating potassium persulfate (PDS) was evaluated through the degradation of Safranine T (ST) in the presence of boron powder (B). The effects of vital parameters on ST removal were systematically studied, including PDS concentration, 3WSHB dosage, initial solution pH, B dosage, temperature and coexisting cations. The highest efficiency of ST removal was up to 93.0% under the optimal condition with 1.85 mM of PDS, 0.3 g/L of 3WSHB, 0.35g/L of B, 7 of pH. EPR and free radical quenching experiments demonstrated that •OH was the dominant reactive oxygen species for ST degradation in the PDS/3WSHB/B system. Moreover, the intermediates determined by HPLC-MS indicated that the oxidization of benzene ring substituents in ST and a hydrogen abstraction by electron transfer might occur during ST degradation. The dissatisfied reuse performance of 3WSHB might be attributed to its low Fe content and simple reusing way. The results demonstrate the effectiveness of WS recycling and reuse in the field of pollutant remediation.

Biochar Amendment in Vermi-Wetland for Enhancing Nitrification during Excess Sludge Recycling

Vermi-wetland is a sustainable technology for recycling excess sludge in small-town areas. Although biochar (BC) amendment into the vermi-wetland could considerably boost the effectiveness of treating sludge, its impact on the nitrogen transformation in vermi-wetland remains unclear. Hence, this study aimed to explore the mechanism and performance of BC amendment into the vermi-wetland for enhancing nitrogen transformation during excess sludge recycling. The semi-aquatic plant Acorus calamus and the earthworm Eisenia fetida were planted in the designed vertical vermi-reactor, with corncob BC added to the upper and lower layers of one vermi-reactor, in comparison with the vermi-reactor without BC. The vermi-reactor with BC significantly lowered (p < 0.05) ammonia nitrogen (NH4+-N) and nitrite nitrogen (NO2−-N) in the effluent by 1.63 and 4.85-fold, respectively, and increased considerably nitrate nitrogen (NO3−-N) in the effluent by 1.5-fold. The numbers of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in the vermi-reactor with BC were greatly enriched by 6 and 1.42-fold, compared with their counterparts (p < 0.05). Moreover, nirS and nirK gene copies in the vermi-reactor with BC were considerably improved (p < 0.05) by 2.03 and 1.82-fold, respectively. BC significantly enhanced the growth of earthworms by 6.92-fold and promoted plant growth by 1.28-fold. In addition, the AOB members like Nitrosomonas and Nitrosospira and the AOA members like Crenarchaeota and Thaumarchaeota cohabited in BC. Overall, these results suggest that a vermi-reactor amended with BC could enhance the nitrification processes of excess sludge, thereby improving the treatment performance of vermi-wetland.

Effect of recycled lime sludge, calcined clay and silica fume blended binder-based fibrous concrete with superior impact strength and fracture toughness

This study investigated the impact strength of fibrous concrete and its mode I, mode III, and mixed-mode I/III fracture toughness. Three binders were produced with varying compositions. The first binder was created by combining 95% clinker and 5% gypsum. The second binder consisted of 50% clinker, 30% calcined clay, 15% recycled lime sludge (RLS), and 5% gypsum. The third binder was composed of 50% clinker, 15% RLS, 30% silica fume, and 5% gypsum. There were three groups of binders used to classify the twelve different mixes. Each group comprises four different concrete mixtures: non-fibrous concrete, conventional fibrous concrete and two functionally graded fibrous concrete (FGFC) with three layers. Short-crimped steel fibres were utilized at an average dosage of 1.5% by volume. The fibre dosage of 2 and 2.25% was used in the top and bottom layers of FGFC and 0 and 0.5% were used in the middle. Besides, a microstructure study was performed to evaluate the strength development phases, utilizing X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis techniques. Findings reveal that the mixture comprising an RLS and calcined clay binder combination exhibited the best compressive and impact strength performance. Introducing a three-layered concrete specimen with higher fibre content at the outer layer exhibits exceptional impact resistance compared to traditional fibrous concrete. Besides, fracture toughness under mode III is more critical than mode I and I/III and an increase in the load angle results in a reduced rate of improvement in fracture toughness.

Recycling sludge in agriculture? Assessing sustainability of nutrient recovery in Italy

Abstract Using a hybrid multi-regional input–output approach, we traced sustainability footprints of a nutrient recovery strategy from sewage sludge applied in Italy. We then compared the results with the most common landfilling practice. Overall, accounting for indirect global upstream effects, using sewage sludge for organic fertiliser production generates more jobs and reduces more greenhouse gas emissions than landfilling. By contrast, landfilling stimulates the whole economy more, generating higher indirect turnover and reduces energy carrier use more. Finally, we accounted for uncertainties in these results using an error propagation method based on Monte Carlo simulations.

Dual oxidant strategy involving calcium peroxide and peroxydisulfate for waste activated sludge recycling: Removal of sulfamethoxazole and hydrocortisone

In this study, the removal of sulfamethoxazole (SMX) and hydrocortisone (HC) from waste activated sludge (WAS) was explored using a dual oxidant strategy involving calcium peroxide (CaO2) and peroxydisulfate (PDS). Synergistic effects were observed between CaO2 and PDS at 0.1 g/g TS (total solids), leading to 89 % and 54 % removal of SMX and HC, respectively, in 8 min in sludge. Ca2+, Ca(OH)2, H2O2, and SO42– from CaO2 and PDS hydrolysis promoted pollutant removal. SMX removal was mainly driven by 1O2, which had a 78 % contribution to the removal rate, while HC removal was mainly due to OH and SO4–, with an overall 79 % contribution. Furthermore, removal pathways for SMX and HC during CaO2/PDS were proposed. SMX, HC, and their intermediates with high toxicity transformed into less toxic or nontoxic products during CaO2/PDS oxidation. Moreover, the dewatering ability and solubility of sludge increased after CaO2/PDS treatment. Furthermore, the production of volatile fatty acids during anaerobic fermentation of sludge pretreated with CaO2/PDS increased by 1.8 times relative to the control, with a 13 % increase in acetic acid content. The altered relative abundance of Firmicutes and Proteobacteria played a key role in promoting the recovery of carbon sources from the sludge.

Generation of green electricity from sludge using photo-stimulated bacterial consortium as a sustainable technology

Microbial fuel cell (MFC) is a bio-electrical energy generator that uses respiring microbes to transform organic matter present in sludge into electrical energy. The primary goal of this work was to introduce a new approach to the green electricity generation technology. In this context a total of 6 bacterial isolates were recovered from sludge samples collected from El-Sheikh Zayed water purification plant, Egypt, and screened for their electrogenic potential. The most promising isolates were identified according to 16S rRNA sequencing as Escherichia coli and Enterobacter cloacae, promising results were achieved on using them in consortium at optimized values of pH (7.5), temperature (30°C) and substrate (glucose/pyruvate 1%). Low level red laser (λ = 632.8nm, 8mW) was utilized to promote the electrogenic efficiency of the bacterial consortium, maximum growth was attained at 210 sec exposure interval. In an application of adding standard inoculum (107 cfu/mL) of the photo-stimulated bacterial consortium to sludge based MFC a significant increase in the output potential difference values were recorded, the electricity generation was maintained by regular supply of external substrate. These results demonstrate the future development of the dual role of MFCs in renewable energy production and sludge recycling.

Operational strategies enhancing sewage sludge minimization in a combined integrated fixed-film activated sludge – oxic settling anaerobic system

A lab-scale integrated fixed-film activated sludge (IFAS) reactor was mplemented with the oxic-settling anaerobic (OSA) cycle for reducing sewage sludge production through the addition of an anoxic/anaerobic sludge holding tank (SHT) along the sludge recycle line. The IFAS-OSA system was operated under the different hydraulic retention time (HRT) in the SHT (HRTSHT) of 12 h and 6 h, at an oxidation-reduction potential (ORP) < −91 mV and solid retention time (SRT) between 39 and 126 d. Furthermore, the effect of temperature increase in the SHT (TSHT) from ambient (19.8–25.6 °C) to mesophilic (35 °C) conditions was investigated. The system performances were monitored in terms of sludge minimization and dewaterability efficiencies as well as carbon and nutrients reduction. The observed sludge yield (Yobs) for the IFAS system was 0.37(±0.06) mg VSS/mg COD. After OSA implementation Yobs decreased by 32% and 46–65% at HRTSHT of 12 h and 6 h, respectively, indicating that prolonged exposure to anoxic/anaerobic conditions was not beneficial for sludge reduction. The lowest Yobs of 0.09(±0.05) mg VSS/mg COD (76% lower than that in the IFAS system) was obtained at an HRTSHT of 6 h and when TSHT was set at 35 °C. OSA implementation did not affect COD and NH4+ oxidation of the IFAS system (90–96% and 99%, respectively) and improved total nitrogen (TN) reduction (31–53%) due to improved denitrification in the SHT. On the contrary, sludge dewaterability worsened following OSA implementation, which was linked to the increased levels of exopolymeric substances in the suspended biomass.

Recycling of cathode ray tubes and stone sludge for the synthesis of Al-MCM-41 grafted amine functional group and environmental humidity control material applications

There is a growing need for economical methods by which to reuse industrial waste. This paper reports on the recycling of industrial waste in the preparation of amine functionalized mesoporous molecular sieves (Al-MCM-41), for use as a building material applicable to the energy-free regulation of indoor humidity. The preparation of amine functionalized Al-MCM-41 for experiments involved combining stone sludge, cathode ray tube panel waste glass, an alkali agent (sodium hydroxide), and cetyltrimethylammonium bromide with aminopropyltriethoxysilane in various proportions. The water vapor adsorption of amine functionalized Al-MCM-41 (42.85 g/m2) far exceeded of amine functionalized Al-MCM-41 without surface grafting (28.64 g/m2). Al-MCM-41 with 2.5 vol% amine functional groups achieved the highest 24-h water vapor adsorption performance in compliance with JIS A 1470 standards. This research provides an economical approach to the recovery and recycling of industrial waste that is rich in silicon and aluminum.

Bifunctional erdite rods as an effective flocculant and catalyst in electro-Fenton systems

Erdite rods were massively produced via a one-step alkaline heating route with the complete recycling of waste waterwork sludge. The sludge was a mixture of Fe, Mn, Al, and Si, but only Fe-bearing substances were converted as erdite rods. The erdite rods had 100 ​nm diameter and 1-5 ​μm length, and was hydrolysed as Fe-SH-rich flocs in wastewater. Its hydrolysis became slow in the presence of electric field but accelerated by adding PMS. p-Nitrophenol was targeted as organic pollutant to determine the rods performance. The removal efficiency of p-nitrophenol was 7.4% by adding erdite rods, but up to 44.6% with the addition of erdite/PMS, and then dramatically increased to 98.7% in the electro-PMS/erdite system. Given that the free Fe was less than 30 ​mg/L, the surface Fe of Fe-SH-rich flocs predominated the PMS activation, in which the surface Fe enriched in electronic field and then was involved in the redox reaction of PMS and then reduced by the adjacent S on flocs. This enabled the recycling of Fe3+/Fe2+ to activate PMS at high level. Thus, the erdite rods showed high p-nitrophenol removal efficiency in the electro-Fenton system in comparison with the other reported reagents, e.g. ferrous sulphate, ferbam, pyrite and FeS.

Oily cold rolling mill sludge conditioned by quicklime to improve dewatering performance: optimization and mechanism study.

Dewatering is critical to oily cold rolling mill (CRM) sludge treatment. Therefore, finding an efficient, energy-saving, and applicable dewatering technology for oily CRM sludge is still urgent. This study investigated the performance of quicklime as a conditioning agent for oily CRM sludge conditioning and dewatering. The interactive effects of quicklime dosage, temperature, and time on filter cake's specific resistance to filtration (SRF) and the dewatering rate of oily CRM sludge were studied by response surface methodology (RSM). The optimal parameters for conditioning oily CRM sludge were quicklime dosage of 18.7%, temperature of 54 °C, and time of 43.3 min, which resulted in filter cake SRF of 0.50 × 1010 m/kg and dewatering rate of 61.2%. The viscosity of oily CRM sludge could be reduced by 90% after conditioned with quicklime, which caused by the neutralization or hydrolysis of high viscosity organic matter in the oil phase with quicklime to produce low viscosity organic matter. The study indicated the excellent performance of quicklime as a conditioning agent for oily CRM sludge treatment and provided an effective route for the recycling of the oily CRM sludge for steel production.

Гальваношламы – источник вторичных материальных ресурсов при получении пигментов-наполнителей для лакокрасочных изделий

Galvanic production occupies one of the first places according to the degree of negative impact on the environment due to the content of heavy metal ions which have toxic, carcinogenic and mutagenic properties. Finding an effective method of recycling and utilization of galvanic sludge will solve the problem of the steady growth of the cost of metals and minimize the negative impact on the environment, which is an important environmental task of great scientific and practical significance. This paper presents the results of studies on the extraction of iron oxide(III) Fe2O3 from ironcontaining galvanic sludge to use it as a filler pigment in the manufacture of paint (red iron oxide). At the initial stage, the original galvanic sludge was dissolved in distilled water to a creamy consistency, and then, sulfuric acid was gradually added until the pH value gradually decreased (pH 6.0–1.5), metal sulfates were obtained. Iron hydroxide(III) Fe(OH)3 was precipitated from filtered sulfate solutions with 40% NaOH alkali solution at pH 1.5–4.1. After preliminary drying at a temperature of ≈ 150 оС, heat treatment was carried out at 600±2 оС for 5–6 h, obtaining iron oxide(III) Fe2O3, which met the requirements of GOST 10503-71 “Oil paints, ready to use. Technical Conditions in terms of particle size, oil capacity, particle density and pH of aqueous extracts. The iron minium paint made on its basis also met the requirements of this GOST on parameters: viscosity, hiding power, drying time, etc. A schematic diagram is proposed for obtaining a filler pigment used for the production of paints and varnishes. The scheme uses a set and layout of equipment widely used in industry (conveyor, batchers, screw feeders, acid and alkali treatment baths, centrifuge, drying and roasting oven).

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.&#x0D; 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.