Sludge Production Research Articles

Bioremediation of Sulfate in Water Environment: An Overview of Removal Pathways and Influencing Factors

Sulfate-laden wastewater generated from various natural and industrial activities, including mining, metallurgy, electroplating, and battery manufacturing and recycling, has the potential to contaminate both ground and surface water bodies. It is harmful to all forms of life and the environment. Thus, developing an efficient treatment system to address sulfate pollution is necessary. Biological sulfate reduction (BSR) involving sulfate-reducing bacteria offers a better removal of sulfate than conventional physicochemical methods. BSR offers various advantageous such as lower sludge production, removal and recovery of metals, and production of elemental sulfur. However, the performance of bioreactors depends on wastewater sources, microbes involved, and operating conditions. Currently, limited studies are available encapsulating the current state of the art of biological sulfate remediation aimed at optimization of bioreactor design and operation. Therefore, this paper attempts to provide a comprehensive review of the sources of sulfate, its health and ecological effects, microbes involved in sulfate reduction, and its removal pathways that would be beneficial for future bioreactor design. In addition, theoretical and practical aspects of influencing factors have been discussed. Considering the results of the reviewed articles, operating, and set-up conditions are recommended to obtain the higher sulfate removal. It includes dissimilatory sulfate reduction by mixed bacterial culture using sodium lactate as an electron donor with pH near about neutral, mesophilic conditions, COD/SO2−4 ratio of 0.67-1.7, ORP less than −100 mV, and lesser sulfide concentration. This overview helps to develop an effective strategy for bioremediation of sulfate and decreasing the sulfate-rich industrial effluent footprint.

A study of continuous-flow electrocoagulation process to minimize chemicals dosing in the full-scale treatment of plastic plating industry wastewater

A continuous-flow electrocoagulation unit was used to replace the existing chemical coagulation in plastic plating industry wastewater treatment plants, aiming to enhance pollutant removal and cost efficiency. This study was conducted at an on-site wastewater treatment plant, with the electrocoagulation process monitored for nine consecutive months. A novel electrocoagulation unit equipped with multi-rod helical systems (i.e., made of an iron anode and a stainless-steel cathode) was used in this study, with the treatment flow adjusted to optimize the operational costs. The results indicate that energy consumption can be maintained at 7200 kWh/month while achieving >99 % removal of heavy metals (Cr, Ni, and Cu), with removal rates of 78.64 ± 0.13 mg/L.day (Cr), 105.47 ± 0.07 mg/L.day (Ni), and 38.30 ± 0.09 mg/L.day (Cu). The chemical cost was reduced by approximately 50 %. Furthermore, an over 50 % reduction in sludge production was achieved, with the acid and alkaline by-products entirely recycled. Compared to the previously applied chemical coagulation, electrocoagulation can reduce operational costs from US$ 6.11 to US$ 2.87 per m3 of wastewater treated. These results confirm that electrocoagulation can be optimized and implemented to replace conventional chemical coagulation.

Research on the Resource Recovery of Medium-Chain Fatty Acids from Municipal Sludge: Current State and Future Prospects.

The production of municipal sludge is steadily increasing in line with the production of sewage. A wealth of organic contaminants, including nutrients and energy, are present in municipal sludge. Anaerobic fermentation can be used to extract useful resources from sludge, producing hydrogen, methane, short-chain fatty acids, and, via further chain elongation, medium-chain fatty acids. By comparing the economic and use values of these retrieved resources, it is concluded that a high-value resource transformation of municipal sludge can be achieved via the production of medium-chain fatty acids using anaerobic fermentation, which is a hotspot for future research. In this study, the selection of the pretreatment method, the method of producing medium-chain fatty acids, the influence of the electron donor, and the technique used to enhance product synthesis in the anaerobic fermentation process are introduced in detail. The study outlines potential future research directions for medium-chain fatty acid production using municipal sludge. These acids could serve as a starting point for investigating other uses for municipal sludge.

Ecological filter walls for efficient pollutant removal from urban surface water

Urban surface water pollution poses significant threats to aquatic ecosystems and human health. Conventional nitrogen removal technologies used in urban surface water exhibit drawbacks such as high consumption of carbon sources, high sludge production, and focus on dissolved oxygen (DO) concentration while neglecting the impact of DO gradients. Here, we show an ecological filter walls (EFW) that removes pollutants from urban surface water. We utilized a polymer-based three-dimensional matrix to enhance water permeability, and emergent plants were integrated into the EFW to facilitate biofilm formation. We observed that varying aeration intensities within the EFW's aerobic zone resulted in distinct DO gradients, with an optimal DO control at 3.19 ± 0.2 mg L−1 achieving superior nitrogen removal efficiencies. Specifically, the removal efficiencies of total organic carbon, total nitrogen, ammonia, and nitrate were 79.4%, 81.3%, 99.6%, and 79.1%, respectively. Microbial community analysis under a 3 mg L−1 DO condition revealed a shift in microbial composition and abundance, with genera such as Dechloromonas, Acinetobacter, unclassified_f__Comamonadaceae, SM1A02 and Pseudomonas playing pivotal roles in carbon and nitrogen elimination. Notably, the EFW facilitated shortcut nitrification-denitrification processes, predominantly contributing to nitrogen removal. Considering low manufacturing cost, flexible application, small artificial trace, and good pollutant removal ability, EFW has promising potential as an innovative approach to urban surface water treatment.

Contribution to the Management and Valorization of Fecal Sludge in the Urban Commune of Kissidougou, Mamou, Republic of Guinea

Background and Aim : This research is a continuation of our work on the management and recovery of domestic waste. Its general objective is to take stock of the fecal sludge in the urban commune of Kissidougou, with a view to proposing appropriate treatment techniques. So, to achieve this objective, we carried out a field survey in the twenty-four neighborhoods of the urban commune, where we met ten households per neighborhood, or two hundred and forty households. Method : The specific production methods, characteristics of sanitation works, demand for mechanical emptying, and turnover of the emptying operator were used Results : The results obtained show that the housing typology of Kissidougou is characterized by a dominance of low standing estimated at 61%, followed by 37% of medium standing compared to only 2% of traditional type. Wastewater and excreta sanitation works are mainly traditional with 61%, followed by septic tanks with 14%, 13% improved latrines, 10% without specific purpose and only 1% VIP. The frequency of emptying is estimated at 40% for between 2 to 5 years, 29% (more than 2 years), 19% of the population surveyed, once the latrines are full, they give up; 7% have not changed their oil for 10 years; Likewise, 51% of the population do manual emptying; while 43% have an imprecise method of emptying their works; 4% empty their works mechanically and only 1% (other and not yet emptied). For a population of nearly 110000 inhabitants, the estimated annual specific production of faecal sludge is 64240 m3/year, or a specific production depending on households of 3014 m3/year. The quantity of sludge mechanically drained per year is 0.4m3/year; that manually is 6.24 m3/year. Thus, the characteristic of the sanitation works gives 314.12 m3/year and that of the operation of the mechanical emptying operator is 730 m3/year. Conclusion : The results show that 30% of the population do not know how much they paid to empty their latrines ; while 18% say they paid 300000 GNF, 13% paid 350000 GNF ; 10% invested 450000 GNF for emptying their latrines, 8% of the population paid 400000 GNF and others 500000 GNF ; 6% of respondents said nothing about the emptying situation ; 5% pay 650000 GNF and 4% do their emptying at 600000 GNF. Keywords: Faecal sludge, sanitation works, Management and recovery

Should wastewater treatment plants' operational mode radically change to minimize GHG emissions?

The operation of municipal wastewater treatment plants (WWTPs) invariably results in significant emission of greenhouse gases (i.e., CH4, N2O, and CO2) into the atmosphere. We propose to consider a radical change in the way municipal WWTPs are operated, with the aim of minimizing GHG emissions while recycling most of the nutrient mass. The means to this end are to reduce the WWTP energy demand while maximizing the recovery of resources (phosphorus, ammonia, methane). The suggested concept involves operating the activated sludge process at a low sludge retention time (SRT < 2 d), i.e., under conditions that maximize the heterotrophic mass yield and eliminate nitrification. The ammonia concentration that remains in the water (considering N in the excess sludge and struvite production in the sludge-dewatering supernatant line) would be separated from the WWTP effluents using a unique ion-exchange material (ZnHCF), which would be regenerated using a low-volume 4 M NaCl solution. The ammonia would be then stripped at high pH and re-adsorbed by an acidic solution for reuse as fertilizer. The high bacterial yield and lack of nitrification in the aerobic step are expected to boost methane yield 3–4-fold, induce lower oxygen consumption, and most importantly, yield much lower N2O release. An approximate energy mass balance shows the concept to merit further consideration, owing to the potential significant reduction in N2O(g) emissions and recovery of resources. Empirical work followed by LCA is required to corroborate the hypothesis presented herein.

CuS assisted Fe(III)-induced peracetic acid activation for bisphenol A degradation: significance of synergetic roles of copper and sulfur in enhanced Fenton-like process

Peracetic acid (PAA), as a promising synthetic organic acid disinfectant, is widely used in advanced oxidation processes to produce radicals for micropollutant abatement. While PAA activation driven by common Fenton-like processes suffers from the slow iron cyclic conversion and production of ferric sludge. This study introduces a metal sulfide, i.e., CuS, to assist the Fe(III)-induced PAA activation via multiple pathways, including the direct PAA activation and Fe(II)/Fe(III) cyclic conversion acceleration, termed as the CuS/Fe(III)/PAA process, to produce •OH, O2•−, Fe(IV), CH3C(O)O•, and CH3C(O)OO•, capable of degrading bisphenol A (BPA), one of representative endocrine disruptors in wastewater, thus overcoming the limitation of conventional Fenton-like processes. Cu(I), S22−, and S2− are determined to be catalytic sites of CuS responsible for the promotion of PAA activation. The CuS/Fe(III)/PAA process exhibits excellent degradation performances under acid conditions and performed high reactivities toward the degradation of various contaminants. The introduction of metal sulfide into the Fe(III)/PAA process improves the PAA activation and micropollutant degradation and reduces accumulation of iron sludge. Of particular significance is that water matrices performed limited effects on the BPA degradation, suggesting the potential of CuS/Fe(III)/PAA process to degrade micropollutants in real water treatment.

Introducing a new method to assess the benefits of resources recovered from wastewater to the natural environment

Resources recovery can improve the economic efficiency and reduce the negative environmental impacts of municipal wastewater treatment plants (MWWTP). The recovered resources can also actively benefit the natural environment enabling a reciprocal relationship between human society and nature. Focusing on these benefits can reveal new resources recovery opportunities. Moreover, for certain environmental impact categories such as emissions of reactive nitrogen, mere damage reduction is insufficient because these emissions are already beyond planetary limits. However, quantitative methods to assess nature benefits are lacking. A new method is developed to calculate the potential nature benefits in three categories: Freshwater restoration, biomass assimilation of nutrients, and soil organic matter sequestration and it is demonstrated on a real-life MWWTP. Focusing on resources recovery helps to purify the wastewater sufficiently for discharge and to benefit the natural environment. Treated wastewater discharge into a river can support freshwater restoration depending on the effluent quality. High quality is achieved by the sufficient removal of the nutrients and organic matter and discharging into a high-flow stream. The recovery of nutrients helps to close the nutrient cycle through biomass assimilation. To maximize this benefit, the nutrient recovery efficiency from the MWWTP must be maximized. But, increasing the nutrient uptake efficiency in agriculture is also crucial, especially for nitrogen. The wastewater sludge products can be applied to soil to sequester organic matter and the products with low volatile solids should be preferred. The development of the new method is a start to recognizing and assessing the potentially positive role of humans in nature.

Enhancement of energy and cost efficiency in wastewater treatment plants using hybrid bio-inspired machine learning control techniques

Global population growth drives demand for clean water, energy, and wastewater production in urban areas. Most existing wastewater treatment plants (WWTPs) are energy- and cost-intensive. To achieve the UN Sustainable Development Goals (SDGs) by 2030, many regions have implemented strict policies for energy consumption and contaminated water discharge, promoting environmental sustainability. This paper attempts to enhance the achievement of SDGs in the wastewater treatment industry by proposing a novel method for hierarchical control of wastewater treatment plants to ensure energy and cost efficiency with less knowledge of the process model, fewer measurements, and fewer control loops. This controller is the combination of a machine learning control technique with a bio-inspired computational algorithm. To evaluate and validate the performance of the proposed controller on the WWTP, the benchmark simulation model no. 1 (BSM1) has been used. The most significant contributions of this paper show that 488.96 KWh/d, 3620.08 Kg/d, and 3454.55 KWh/d of aeration energy cost index, sludge production cost index, and operational cost index are respectively saved when compared to the default control strategy (DCS). Also, 893.69 Kg pollution units per day of effluent fine-related costs have been successfully recovered when compared to the DCS. The experimental results illustrate that the proposed control yields significant amelioration of the energy and cost profile of the WWTP with no effluent violation in dry, rain, and storm weather conditions.

Revealing the differences in metabolisms and nitrogen removal mechanisms of the full and shortcut nitrification-denitrification processes for the treatment of livestock wastewater

The full nitrification-denitrification process (FN) and shortcut nitrification-denitrification process (SN) are both important approaches for treating livestock wastewater. However, most existing studies focus on pollutant removal performance in wastewater treatment, while the differences between the two processes in terms of bacterial communities, metabolic pathways, nitrogen removal mechanisms, and potential pathogen threats have been poorly investigated. In this study, the SN process exhibited lower oxygen demand, reduced sludge production, higher nitrogen removal rate, and lower pathogen threat for treating livestock wastewater. The bacterial communities, the primary participants of pollutant removal in wastewater treatment, were significantly different between the two processes. In the FN process, 15 genera were significantly enriched, including Saccharimonadales, Micropruina, Ferruginibacter, etc. On the other hand, the SN process showed enrichment of 10 genera, including Brachymonas, Tessaracoccus, Ottowia, etc. These enriched genera, such as Brachymonas, Tessaracoccus, and Ottowia in the SN process, were positively correlated with the denitrification genes, facilitating a higher nitrogen removal rate. Moreover, the FN process exhibited significantly higher amino acid metabolism and reproduction-related pathways, contributing to its higher alpha-diversity of the bacterial community. The significantly enriched genes involved in assimilatory nitrate reduction and nitrogen assimilation pathway suggested that nitrogen assimilation played a crucial role in ammonia nitrogen removal, but it also increased sludge production in the FN process. Additionally, the FN process had a higher number and abundance of potential pathogens, indicating a greater pathogen threat. In conclusion, this study provides valuable insights into the differences between the FN and SN processes in terms of bacterial communities, nitrogen removal mechanisms, and potential pathogen threats. It also offers theoretical guidance for adopting appropriate strategies in wastewater treatment.

The effect of aeration mode (intermittent vs. continuous) on nutrient removal and greenhouse gas emissions in the wastewater treatment plant of Corleone (Italy)

The paper reports the results of an experimental study aimed at comparing two configurations of a full-scale wastewater treatment plant (WWTP): conventional activated sludge (CAS) and oxic-settling-anaerobic process (OSA) with intermittent aeration (IA). A comprehensive monitoring campaign was carried out to assess multiple parameters for comparing the two configurations: carbon and nutrient removal, greenhouse gas emissions, respirometric analysis, and sludge production. A holistic approach has been adopted in the study with the novelty of including the carbon footprint (CF) contribution (as direct, indirect and derivative emissions) in comparing the two configurations. Results showed that the OSA-IA configuration performed better in total chemical oxygen demand (TCOD) and ortho-phosphate (PO4-P) removal. CAS performed better for Total Suspended Solids (TSS) removal showing a worsening of settling properties for OSA-IA. The heterotrophic yield coefficient and maximum growth rate decreased, suggesting a shift to sludge reduction metabolism in the OSA-IA configuration. Autotrophic biomass showed a reduced yield coefficient and maximum growth yield due to the negative effects of the sludge holding tank in the OSA-IA configuration on nitrification. The OSA-IA configuration had higher indirect emissions (30.5 % vs 21.3 % in CAS) from additional energy consumption due to additional mixers and sludge recirculation pumps. The CF value was lower for OSA-IA than for CAS configuration (0.36 kgCO2/m3 vs 0.39 kgCO2/m3 in CAS).

BioWin Modeling of CalPrex Phosphorus Recovery from Wastewater Predicts Substantial Nuisance Struvite Reduction

The wastewater treatment industry could benefit from new technologies for the removal and recovery of phosphorus (P). The CalPrex precipitation reactor has the potential to recover P in a readily land-applicable form by treating organic acid digestate with calcium hydroxide to produce brushite. Using data from a pilot-scale reactor at the local Nine Springs Wastewater Treatment Plant in Madison, WI, we modified the plant’s BioWin configuration using BioWin 6.2 to model the CalPrex technology and estimate performance under a variety of conditions. We produced dose/response curves for a range of possible lime dosages to estimate the impact of reagent dosage on the quantity and composition of precipitate produced by the CalPrex reactor and characterize the effects on downstream anaerobic digester performance. CalPrex was found to capture 46% of the plant’s influent P, reducing nuisance struvite precipitates by 57% and biosolid sludge production by 14%. The CalPrex module was also tested in two predesigned plant configurations in the BioWin cabinet with the intention of testing applicability to other configurations and searching for the impacts of CalPrex on treatment train performance. This is the first work simulating a full-scale implementation of CalPrex and the first to model interactions of CalPrex with other treatment processes.

Surfactant enhanced persulfate system for the synergistic oxidation and reduction of mixed chlorinated hydrocarbons

Surfactant-enhanced in-situ chemical oxidation (S-ISCO) is widely applied in soil and groundwater remediation. However, the role of surfactants in the reactive species (RSs) transformation remains inadequately explored. This work introduced nonionic surfactant Tween-80 (TW-80) into a nano zero-valent iron (nZVI) activated persulfate (PS) system. The findings indicate that PS/nZVI/TW-80 system can realize the concurrent removal of trichloroethylene (TCE), tetrachloroethene (PCE), and carbon tetrachloride (CT), whereas CT cannot be eliminated without TW-80 presence. Further analysis unveiled that hydroxyl (HO•) and sulfate radicals (SO4－•) were the primary species for TCE and PCE degradation, while CT was reductively eliminated by surfactant radicals generated from TW-80. Moreover, the surfactant radicals were found to accelerate Fe(III)/Fe(II) cycle, reduce the production of iron sludge, and increase PS decomposition. The possible degradation routes of mixed chlorinated hydrocarbons (CHCs) and the decomposition pathways of TW-80 were proposed through the density function theory (DFT) calculation and intermediates analysis. Additionally, the effects of other nonionic surfactants on the simultaneous removal of TCE, PCE, and CT, and the practical applications using the actual contaminated groundwater were also evaluated. This study provides theoretical support for the simultaneous removal of CHCs, particularly those containing perchlorinated contaminants, using the S-ISCO techniques.

A systematic overview of current advancements for chemical, material, and energy production using sewage sludge for industrial ecology and sustainability transition

AbstractUrbanization and population expansion have increased the demand for scarce resources such as land, water, food, and energy. Furthermore, it has heightened environmental concerns, such as pollution and waste management. The difficulties above present significant challenges to the broader goal of attaining global sustainable development. As a result, there is considerable concern about sustainable waste recycling and management solutions. Among these efforts, expanding wastewater treatment facilities has emerged as a critical tool for environmental protection. As a result of the growth of wastewater treatment facilities, there has been a significant increase in sewage sludge (SS) production. Consequently, an urgent need exists to investigate alternative treatment and value-added methods for sewage sludge. This review looks at the current state of sewage applications for energy and resource recovery to foster sustainable development and industrial ecology through sewage sludge feedstocks. Furthermore, it aims to promote additional research into improving existing sewage sludge management systems, ensuring their cost-effectiveness, public acceptance, and environmental sustainability.

The anaerobic exposure time (AET) as a novel process parameter in the anaerobic side-stream reactor (ASSR)-based process for excess sludge minimization

Minimization of excess sludge produced by wastewater treatment plants has become a topical theme nowadays. One of the most used approaches to achieve this aim is the anaerobic side-stream reactor (ASSR) process. This is considered affected by the hydraulic retention time (HRT) of the anaerobic reactor, the anaerobic sludge loading rate (ASLR) and the sludge interchange ratio (SIR), although, studies available in the literature did not reflect a clear relationship with the sludge minimization yields.To overcome this, a novel parameter namely anaerobic exposure time (AET) was defined and related to reduction of the observed yield coefficient (Yobs) in a lab-scale plant implementing the ASSR process. Furthermore, the AET was validated by performing a detailed and thorough review of previous literature. Excess sludge production was successfully reduced (10–60 %) with the increase of the AET (7.9–13 h/d), although maintaining the same HRT in the ASSR and a constant sludge interchange ratio (SIR) (100 %). A strong correlation (Pearson = 0.763) was found between the AET, and the Yobs reduction reported in previous studies, also indicating a linear relationship (R2 = 0.92) between these parameters. Contrarily, the correlation between the Yobs with the ASLR and the ASSR-HRT resulted moderate (Pearson = 0.186) or weak (Pearson=−0.346), respectively. Overall, while operating at low AET (< 6 h), maintenance and uncoupling metabolism were found the main sludge reduction mechanisms. Increasing the AET (>8 h) favoured the occurrence of extracellular polymeric substances (EPS) hydrolysis and endogenous decay mechanisms, which improved excess sludge reduction. To conclude, the AET could be considered a reliable parameter to be used for design or control purposes for the ASSR-based process.

Enhancement of medium-chain fatty acids production from sludge anaerobic fermentation liquid under moderate sulfate reduction

In recent years, there has been a marked increase in the production of excess sludge. Chain-elongation (CE) fermentation presents a promising approach for carbon resource recovery from sludge, enabling the transformation of carbon into medium-chain fatty acids (MCFAs). However, the impact of sulfate, commonly presents in sludge, on the CE process remains largely unexplored. In this study, batch tests for CE process of sludge anaerobic fermentation liquid (SAFL) under different SCOD/SO42− ratios were performed. The moderate sulfate reduction under the optimum SCOD/SO42− of 20:1 enhanced the n-caproate production, giving the maximum n-caproate concentration, selectivity and production rate of 5.49 g COD/L, 21.4% and 4.87 g COD/L/d, respectively. The excessive sulfate reduction under SCOD/SO42− ≤ 5 completely inhibited the CE process, resulting in almost no n-caproate generation. The variations in n-caproate production under different conditions of SCOD/SO42− were all well fitted with the modified Gompertz kinetic model. Alcaligenes and Ruminococcaceae_UCG-014 were the dominant genus-level biomarkers under moderate sulfate reduction (SCOD/SO42− = 20), which enhanced the n-caproate production by increasing the generation of acetyl-CoA and the hydrolysis of difficult biodegradable substances in SAFL. The findings presented in this work elucidate a strategy and provide a theoretical framework for the further enhancement of MCFAs production from excess sludge.

Hybrid Fenton-electrochemical reactor and system as post-treatment of textile wastewater

Textile effluents contain different kinds of chemical additives and mostly are treated by biological processes. However, COD, ammonium, and color cannot be removed completely from wastewater. Decolorization agents are commonly used as a post-treatment method, although high cost and hazardous sludge byproduct are often reported as their main weaknesses. This study proposes a hybrid system of Fenton and electrochemical to replace the costly decolorization agents, as it is low-cost and highly efficient with no sludge production. This system consists of one cylindrical reactor with a working volume of 50 L and 12 pairs of Ti/RuO2 mesh cylinder and graphite carbon rod electrodes. It was also equipped with wastewater tank, pump, power supply, mixer, pH meter, and ammonia meter. The effects of wastewater volume, potential, retention time, pH, mixing speed, ferrous sulphate and salt concentration on COD, ammonium, and color removals were investigated and discussed. This system was able to reduce color, COD, and ammonium significantly in 15 min for 96 %, 64 %, and 77 %, respectively, at 4000 mg/L salt concentration, 30 mg/L ferrous sulphate, pH 4, 90 rpm mixing speed, and 6 V potential. pH was increased to 6.18; 6.73; 7.25 and 7.36 after 15, 30, 45 and 60 min, respectively. A circulatory system was applied to improve pollutants removal efficiency and electrochemical oxidability index as well as to reduce energy consumption. In terms of reactor performance and operating cost, this system is deemed feasible and applicable as a post-treatment method to support anaerobic-aerobic unit of textile WWTP.

Development of an environmentally sustainable technique to minimize the sludge production in the textile effluent sector through an electrokinetic (EK) coupled with electrooxidation (EO) approach.

This study presents an environmentally sustainable method for minimizing sludge production in the textile effluent sector through the combined application of electrokinetic (EK) and electrooxidation (EO) processes. AAS and XRF analyses reveal that utilizing acidic electrolytes in the EK method successfully eliminates heavy metals (Cu,Mn, Zn, and Cr) from sludge, demonstrating superior efficiency compared to alkaline conditions. In addition, the total removal efficiency of COD contents was calculated following the order of EK-3 (60%), EK-1 (51%) and EK-2 (34%). Notably, EK-3, leveraging pH gradient fluctuations induced by anolyte in the catholyte reservoir, outperforms other EK systems in removing COD from sludge. The EK process is complemented by the EO process, leading to further degradation of dye and other organic components through the electrochemical generation of hypochlorite (940ppm). At an alkaline pH of 10.0, the color and COD removal were effectively achieved at 98 and 70% in EO treatment, compared to other mediums. In addition, GC-MS identified N-derivative residues at the end of the EO. This study demonstrates an integrated approach that effectively eliminates heavy metals and COD from textile sludge, combining EK with EO techniques.

Thermal methods of sludge processing—are they suitable for pharmaceuticals and illicit drugs removal from sewage sludge?

AbstractThe presented work aimed to investigate the effect of thermal treatment on sludge from wastewater treatment plants (WWTPs) in the Slovak Republic on the content of pharmaceuticals (PhACs) and illicit drugs. Sludge samples from eight WWTPs (total flows of 6900–62,500 m3/day, number of population equivalents over 40,000 for each WWTP, production of sludge 400–3300 tons DM/year) were treated with thermal processes in the temperature range of 80 to 550 °C. More than 100 compounds were studied in the sludge samples, but in this article, we deeply focused on the fate of the thirteen most concentrated and frequently found PhACs (azithromycin, carbamazepine, cetirizine, citalopram and its metabolite N-desmethylcitalopram, diclofenac, fexofenadine, sertraline and its metabolite norsertraline, telmisartan, trazodone, valsartan, and verapamil). The thermal processes used showed a decrease in PhAC concentrations already at 80 °C when the total concentration of selected PhACs decreased to 81%. In thermally treated sludge samples at 250 °C, only telmisartan at all studied WWTPs and diclofenac at WWTP Banská Bystrica stayed above the limits of quantification (LOQs), while the temperature of 550 °C led to a decrease in all thirteen PhACs below LOQs.

Reuse of Sewage Sludge as Organic Agricultural Products: An Efficient Technology-Based Initiative

Rapid urbanisation has led to a dramatic increase in sewage sludge production. There are limited methods of managing sewage sludge along with high energy and monetary investment. A cost-effective, environment-friendly, and sustainable solution needs to be developed for the management of sewage sludge. In the current study, sludge from the Jagjeetpur sewage treatment plant (STP) had been collected, composted, and characterized during January and February 2022. A comparison of STP sludge compost and compost made from farmyard manure showed the presence of essential agricultural nutrients in them, due to which they find application for plant growth. Two products, Jaivik Poshak and Jaivik Prom, containing farmyard compost, were compared with the amended version of the same, containing compost from STP sludge instead of normal compost. The results showed that the modified Jaivik Poshak was the best for maintaining pH and increasing electrical conductivity. The available nitrogen in the soil upon its application increased by 1.6 times (p&lt;0.001) with respect to control, and it brought about 100% tomato seed germination within sixteen days. The above finding has been validated by goodness of fit value, factor analysis, and hierarchical analysis. The product, modified Jaivik Prom increased organic carbon content and brought about 5.81 and 8 times the enhancement in available phosphorous (p&lt;0.001) and potassium (p&lt;0.001) content in soil, respectively, with respect to the control set. The heavy metal content in the soil as a result of all types of treatment was within the permissible limit. This study thus proves that sludge from STP may be used for agricultural uses after proper fortification and testing to convert waste to wealth along with environmental sustenance.