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Though chlorine is a cost-effective disinfectant for water and wastewaters, the bacteria surviving after chlorination pose serious public health and environmental problems. This review critically assesses the mechanism of chlorine disinfection as described by various researchers; factors affecting chlorination efficacy; and the re-growth potential of microbial contaminations in treated wastewater post chlorination to arrive at meaningful doses for ensuring health safety. Literature analysis shows procedural inconsistencies in the assessment of chlorine tolerant bacteria, making it extremely difficult to compare the tolerance characteristics of different reported tolerant bacteria. A comparison of logarithmic reduction after chlorination and the concentration-time values for prominent pathogens led to the generation of a standard protocol for the assessment of chlorine tolerance. The factors that need to be critically monitored include applied chlorine doses, contact time, determination of chlorine demands of the medium, and the consideration of bacterial counts immediately after chlorination and in post chlorinated samples (regrowth). The protocol devised here appropriately assesses the chlorine-tolerant bacteria and urges the scientific community to report the regrowth characteristics as well. This would increase the confidence in data interpretation that can provide a better understanding of chlorine tolerance in bacteria and aid in formulating strategies for effective chlorination.

A pulsating floc blanket clarifier (PFBC) employing cyclic contractions and rarefactions to a bed of densely concentrated suspension of flocculated particles in a fluidized state, was compared with conventional clariflocculator (CC) at pilot scale (8,000 L/day) in continuous mode of operation. For influent turbidity varied from 2 to 20 NTU, coagulation-flocculation behavior exhibited under the two fundamentally different treatment processes with PACl influenced inter-related performance parameters. The residual turbidity was found to be lower by 74%, flocs and fine colloids in suspension larger by 73 and 75% respectively, and the total and dissolved residual aluminum lower by 50 and 49% respectively on average for PFBC compared to CC. Particulate form comprised major fraction (≈72%) of total residual aluminum for both. PFBC abetted formation of a more consolidated floc structure, which rendered the shape, size and morphology such that the settling velocity was 50% to 410% higher than that of the CC flocs. Reaction-limited aggregation (RLA) process and inter-particle bridging were dominant and the resulting floc structure and its formation mechanism have been presented. HIGHLIGHTS Pulsating floc blanket significantly alters the floc characteristics.; Pulsating action of the floc blanket affects aggregation patterns at submicron levels.; PFBCs give lower turbidity and residual aluminum compared to CCs.; Particulate form comprises major fraction (≈ 72%) of total residual aluminum.; Inter-particle bridging and reaction-limited aggregation (RLA) dominate at pilot-scale with PACl.

This study presents a performance analysis in terms of energy and other costs related to the unit cost of water produced in 16 identical community scale reverse osmosis units installed at Jaipur. The energy consumptions indicated that these plants suffer from accelerated fouling of membranes due to scaling by hardness causing substances, which results in a significant loss of useful life of the membranes. The study shows that the overall cost of water production has four major components. Energy cost varies between Rs. 0.025 and 0.079 per litre. Salary cost varies between Rs. 0.04 to 0.20 per litre. Spares and chemical cost varies between Rs. 0.01 to 0.04 per litre. In addition, repayment of capital invested has also been considered with and without solar integration to arrive at realistic cost estimates over a perceived life cycle of the system. The breakeven achieved by selling 4600–5200 litre water @ Rs. 0.2 per litre per day if repayment of capital investment is not considered, as these units were installed under CSR, while it varies between 8800 and 9600 litre if repayment of capital investment is also considered as an independent business venture. This analysis substantiates that potential exists for the long-term sustainability of these systems.

About 3,500 small community based reverse osmosis (RO) plants have been installed in Rajasthan, India to comply with the recent Government of India guidelines for drinking water quality in rural areas. This paper presents the performance of four RO plants of Bharatpur, which face frequent replacement of membrane modules primarily due to accelerated scaling of carbonates and sulphates of calcium. A detailed chemical analysis of different streams from these plants was carried out to assess the reasons of scaling through a mass balance approach. The chemical analysis was substantiated through ion balance and the scaling potentials were analysed through different saturation indices. Efficacy of antiscalant usage plants was further assessed through mass balance approach followed by detailed characterization of the RO membrane to understand the complete fouling process, which brought out subtle differences in brackish and seawater desalination. The membranes adopting commonly used antiscalant showed an enhanced life span of 2–2.5 year by reducing calcium carbonate scaling but not calcium sulphate scaling. This study highlights the requirement of customized antiscalant application according to the feed characteristics. With a better understanding of the fouling phenomenon, this study would help enhance the life of membrane in RO plants treating brackish water. HIGHLIGHTS Inorganic scaling is the major challenge in brackish water RO treatment system.; Scaling mechanism is discussed through the calculation of chemical parameters and saturation indices.; Efficacy of antiscalant toward calcium carbonate scaling is discussed and validated through SEM-EDS analysis.

The role of water quality, particularly its impact on health, environment, and wider well-being, are rarely acknowledged in the water–energy–food (WEF) nexus. Here we demonstrate the necessity for including water quality within the water dimension of the WEF nexus to address complex and multi-disciplinary challenges facing humanity. Firstly, we demonstrate the impact of water quality on the energy and food dimensions of the WEF nexus and vice versa at multiple scales, from households to cities, regions and transboundary basins. Secondly, we use examples to demonstrate how including water quality would have augmented and improved the WEF analysis and its application. Finally, we encourage hydrological scientists to promote relevant water quality research as addressing WEF nexus challenges. To make tangible progress, we propose that analysis of water quality interactions focuses initially on WEF nexus “hotspots”, such as cities, semi-arid areas, and areas dependent on groundwater or climate change-threatened meltwater.

Excess fluoride (F) ion of drinking water is a major problem in many areas of India and causes harmful effects such as dental and skeletal fluorosis. The World Health Organization (WHO 2004) recommends an upper limit of 1.5 mg/L fluoride in drinking water, and the concentration of fluoride in groundwater has been found 10-20 times higher in many of the States in India. In this study, the performance of inorganic polymeric coagulant (IPC) named as IPC-23, IPC-13, IPC-17, and alum for fluoride removal from drinking water was investigated. The amount of IPC was decided according to the Al2O3 amount present in the alum dose recommended in the batch Nalgonda defluoridation technique. The effects of coagulant dosage (IPC) at different pH and initial concentrations of fluoride on fluoride removal have been studied. The synthetic sample having a fluoride concentration of 2 to 6 mg/L was treated at the optimized dosage and residual fluoride was reduced to 1.0 to 1.2 ppm with IPC-17. Residual aluminum in treated water was well within WHO norms (< 200 μg/L) for drinking water. Optimum pH for fluoride removal was 6.5, and there was deterioration in the performance of IPC at both lower and higher pH.

Fluoride, an anionic pollutant, existing in concentrations exceeding the allowed limit of 1.5 mg/L in drinking water, has been reported to cause detrimental impact on human health. The traditionall...

Present study aims to investigate how is soil affected following irrigation with treated effluents of different origins by analysing the bacterial diversity, metabolic diversity and antibiotic resistance genes (ARGs). Comparative analysis with previously reported ARGs in effluents was performed to understand the mobility of ARGs from treated wastewater to the irrigated soil with respect to the control soil regimen. Acinetobacter, Burkholderia and Pseudomonas were observed as the most abundant genera in all the samples. The metabolic gene abundance of all the samples suggests a prominent contribution to natural mineral recycling. Most abundant ARGs observed encode resistance for clindamycin, kanamycin A, macrolides, paromomycin, spectinomycin and tetracycline. Treated effluent reuse did not appear to enhance the ARG levels in soils in most cases except for institutional treatment site (M), where the ARGs for aminoglycosides, β-lactams and sulfonamides were found to be abundantly present in both treated effluent and the irrigated soil. This study finds the importance of wastewater treatment from different origins and the impact of treated wastewater reuse in irrigation. This study also emphasises on the better understanding of ARGs mobility from water to soil.

The present study tracked the city-wide dynamics of severe acute respiratory syndrome-corona virus 2 (SARS-CoV-2) RNA in the wastewater from nine different wastewater treatment plants (WWTPs) in Jaipur during second wave of COVID-19 out-break in India. A total of 164 samples were collected weekly between February 19th and June 8th, 2021. SARS-CoV-2 was detected in 47.2% (52/110) influent samples and 37% (20/54) effluent samples. The increasing percentage of positive influent samples correlated with the city’s increasing active clinical cases during the second wave of COVID-19 in Jaipur. Furthermore, WBE based evidence clearly showed early detection of about 20 days (9/9 samples reported positive on April 20th, 2021) prior to the maximum cases & maximum deaths reported in the city on May 8th, 2021. The present study further observed the presence of SARS-CoV-2 RNA in treated effluents at the time window of maximum active cases in the city even after tertiary disinfection treatments of UV & Chlorine. The average genome concentration in the effluents and removal efficacy of six commonly used treatments; Activated Sludge Treatment + Chlorine disinfection (ASP + Cl2), Moving Bed Biofilm Reactor (MBBR) with Ultraviolet radiations disinfection (MBBR + UV), MBBR + Chlorine (Cl2), Sequencing Batch Reactor (SBR) and SBR + Cl2 were compared with removal efficacy of SBR + Cl2 (81.2%)> MBBR + UV (68.8%) > SBR (57.1%) > ASP (50%) > MBBR + Cl2(36.4%). The study observed the trends & prevalence of four genes (E, RdRp, N, and ORF1ab gene) based on two different kits and found that prevalence of N> ORF1ab >RdRp> E gene, suggested that the effective genome concentration should be calculated based on the presence/absence of multiple genes. Hence, it is imperative to say that using a combination of different detection genes (E, N, RdRp & ORF1ab genes) reduce false positives in WBE.Graphical AbstractHighlightsSuccessful application of WBE with prediction of 14-20 days for COVID-19 in JaipurA comparison of SARS-CoV-2 RNA removal efficacy of 9 WWTPs was investigatedSBR showed better performance than MBBR with SARS-CoV-2 RNA removal from wastewaterPresence of SARS-CoV-2 in effluents even after UV and Chlorine disinfectionUsing a combination of different detection genes reduce false positives in WBE

Determining the microbial quality of drinking water by assessing the presence/absence (P/A) or enumeration of indicator bacteria continues to be widely practiced worldwide. However, rapid tests are required for microbiological water quality assessment so that the information is available in the shortest possible time for initiating a timely intervention. Traditional methods for the enumeration of indicator bacteria are not only expensive but also need trained personnel. We have developed a low-cost kit, MColiPAT, and have validated its application for detection of coliforms in drinking water using the IDEXX Colilert-18 Quanti tray method. MColiPAT kit medium was able to detect coliforms down to a level of 3.1 MPN/100 ml within 10.5 hours. The sensitivity and specificity of the kit were 95.45% and 100% respectively. MColiPAT is found to be reliable and accurate for the detection of coliforms in drinking water.

Community water defluoridation plants primarily use activated alumina (AA) for treatment. However, this process generates toxic AA-sludge for which no sustainable method of disposal is currently known. This study evaluated whether AA-sludge could be partially used in manufacturing bricks that are structurally stable and non-polluting. The AA-sludge was variably mixed with soil (0%, 5% and 10% by weight) and fired in a field kiln to produce bricks. These bricks were extensively tested for their structural, non-structural and leaching properties. Up to 10% replacement of conventional clay soil with AA-sludge could be recommended for low-end structural applications.

In the present study, sludge produced from the continuous defluoridation set-up was used as partial replacement for fine aggregates in mortar making. Aluminium sulphate (alum) and polyaluminium chloride (PACl) were used as coagulants for fluoride removal and mortar cubes with size of 50 mm × 50 mm × 50 mm were prepared with alum and PACl sludge in different proportions, i.e. 0%, 1%, 2%, 3%, 4% and 5%. The compressive strength tests were conducted and it was observed that the strength of mortar with 1% replacement increased by 2.5% for alum sludge and 6% for PACl sludge and the compressive strength showed satisfactory values up to 3% sludge replacement for alum and PACl sludge. The impact of partially replacing alum and PACl sludge on the strength of mortars regarding calcium silicate hydrate gel, silica and other hydration products was studied. Toxic Characteristics Leaching Procedure was performed for the mortars and aluminium concentration was within the permissible limits of 0.2 ppm. The results suggested that the reuse of alum and PACl sludges can lead to new paths in reducing the deterioration of the ecosystem because of waste disposal.

Measurement of nitrate nitrogen is relatively less easy and reliable, given the complexity of analytical procedures already marred by interferences. Interfering constituents like organics a...

This paper explores the effect of hybrid chlorine and UV disinfection treatment against their individual usage on microbial community, functional genes, antibiotic resistant genes (ARGs) and disinfection by-products (DBPs) formation. The disinfectant doses of 2.5 mg L−1 chlorine and 41 mJ cm−2 UV were selected based on the coliform counts to be attained in treated sewage. The highest bacterial diversity was observed in control (secondary treated) sample followed by UV, chlorine and hybrid disinfection. The highest elimination of bacterial species (296) was achieved in hybrid treatment, which was far better than the standalone treatments. The disinfection with all the disinfectants used resulted in increased abundance of ARGs. Motility genes were found to be enriched in hybrid disinfected samples. DBP concentrations were within the stipulated norms for all the disinfectant treatments used. Hybrid disinfection was observed to be more effective in alleviating the risks associated with the reuse of treated sewage.

With the global concern on the role of wastewater treatment technologies in manifesting the emergence and dissemination of antibiotic-resistant bacteria (ARB), it has now become imperative to analyze the emerging technologies for handling them. This study assesses the efficiency of two deep constructed wetlands (CWs) receiving partially treated sewage from a residential complex and a hospital designed for the removal of organics and pathogens. These systems were further analyzed for the presence of major ARB to identify the role of CWs in mitigating antibiotic resistance among microbial communities. The bacterial community responsible for metabolic conversions was analyzed by metagenomic sequencing. Finally, the efficiencies of deep CWs were analyzed for the removal of specific bacteria resistant to three antibiotics—piperacillin, colistin (polymixin E), and cefoperazone. The overall removal of extended spectrum beta lactamase producers and carbapenemase producers was also studied. Our results indicate that CWs offer decent BOD and COD removal efficiencies of 74.04–78.71% and 53.85–64.37% respectively. However, a zero-order reaction between loading rate and removal rate was obtained after loading rate of 170 g/m2.day indicating the organic loading capacity of the system. Metagenomic analysis revealed the presence of bacteria with diverse metabolic potentials for substrate conversion. Removal of fecal coliforms was high in the CWs, but the most interesting observation was the attenuation in ARB, which was found to be comparable to, or even better, than the reported values from conventional moving bed bioreactor. This observation may be attributed to the high retention times offered by CWs compared to that of conventional systems making them an attractive future alternative for treating domestic as well as hospital sewage for emerging pollutants.

The present study investigated the detection of severe acute respiratory syndrome– coronavirus 2 (SARS-CoV-2) genomes at each treatment stage of 14 aerobic wastewater treatment plants (WWTPs) serving the major municipalities in two states of Rajasthan and Uttarakhand in Northern India. The untreated, primary, secondary and tertiary treated wastewater samples were collected over a time frame ranging from under-lockdown to post-lockdown conditions. The results showed that SARS-CoV-2 RNA was detected in 13 out of 40 wastewater samples in Jaipur district, Rajasthan and in 5 out of 14 wastewater samples in the Haridwar District, Uttarakhand with the E gene predominantly observed as compared to the N and RdRp target genes in later time-points of sampling. The Ct values of genes present in wastewater samples were correlated with the incidence of patient and community cases of COVID-19. This study further indicates that the viral RNA could be detected after the primary treatment but was not present in secondary or tertiary treated samples. This study implies that aerobic biological wastewater treatment systems such as moving bed biofilm reactor (MBBR) technology and sequencing batch reactor (SBR) are effective in virus removal from the wastewater. This work might present a new indication that there is little to no risk in relation to SARS-CoV-2 while reusing the treated wastewater for non-potable applications. In contrast, untreated wastewater might present a potential route of viral transmission through WWTPs to sanitation workers and the public. However, there is a need to investigate the survival and infection rates of SARS-CoV-2 in wastewater. Published version This research was funded by research grants from the Department of Biotechnology-GoI [Grant No. BT/RLF/Re-entry/12/2016].

The presence of dye in water stream leads to unexceptional effects on living life. As dyes are consumed globally from small-scale to large-scale industries inculcating tanneries, food, cosmetic, textile, medicinal sectors with the production of 1,000,000 tons all over the world. Majorly, the textile sector plays a pertinent role in dye emissions into the ecosystem. Only dying industries discharge about 7.5 metric tons annually. The complex structures of dye comprising of aromatic rings bonded with different functional groups having π-electron could absorb light within 380–700 nm spectra. They impart coloration due to the presence of chromogens and chromophores. Out of several natural and synthetic dyes, azo group proliferation has been highly carcinogenic due to amine and benzidine emissions. Besides this, the fact of being non-biodegradable makes the dye molecules last longer in the environment producing hazards. Henceforth, eradication of dye molecules from wastewater is thus needed before discharging the stream into the environment with long- and short-term effects. The severe implications have been reported for the aquatic life due to direct contact. Whereas to human life, there were observations from skin irritations to cancer-like disease. Several approaches were reported for the treatment of dye-containing streams but the exploration for the best available technique is still ongoing. So, this chapter collects comprehensive facts about dyes, its harmful effect, and approaches for the treatment at a worldwide level and Indian perspective. Additionally, the article draws out the comparative analysis for available techniques and states the recent advancements for the purification of dye-containing wastewater.

Continuous upflow pilot plants based on conventional clariflocculation (CC) and pulsating floc blanket clarification (PFBC) technologies were designed and fabricated for a capacity to treat about 8,000 L/day, to understand the fundamental differences in their functioning and assess their relative performance, especially under low turbidity conditions. Influent turbidity varying from 2 to 10 NTU was treated using coagulant alum, and efficiency of CC and PFBC in terms of average turbidity removal was found to be 23% and 48%, respectively. On observing this vast difference, it was postulated that total residual aluminum should also be lower in water treated from PFBC. Experiments and MLR analysis confirmed the hypothesis, with residual aluminum ranging from 0.055 to 0.040 mg/L and 0.036 mg/L to below detectable levels for CC and PFBC, respectively. These findings are of high significance, since minimization of residual aluminum in drinking water is a priority of WHO due to its reported neurotoxicity and can be complied with simple replacement of CC with PFBC. PRACTITIONER POINTS: Pulsating floc blanket clarifier (PFBC) performed better than conventional clariflocculator (CC) in terms of turbidity removal. Pulsating floc blanket allowed more effective utilization of coagulant alum, resulting in significantly lower residual aluminum in clarified water. Turbidity levels of influent and effluent are related to residual aluminum in treated water. PFBCs are more compact and modular, and can facilitate a good alternative to CCs.

The infection with SARS-CoV-2 is reported to be accompanied by the shedding of the virus in stool samples of infected patients. Earlier reports have suggested that COVID-19 agents can be present in the fecal and sewage samples and thus it can be a good indication of the pandemic extent in a community. However, no such studies have been reported in the Indian context so far. Since, several factors like local population physiology, the climatic conditions, sewage composition, and processing of samples could possibly affect the detection of the viral genome, it becomes absolutely necessary to check for the presence of the SARS-CoV-2 in the wastewater samples from wastewater treatment plants (WWTPs) serving different localities of Jaipur city, which has been under red zone (pandemic hotspots) since early April 2020. Samples from different local municipal WWTPs and hospital wastewater samples were collected and wastewater based epidemiology (WBE) studies for the presence of SARS-CoV-2 were carried out using the RT-PCR technique to confirm the presence of different COVID-19 target genes namely S gene, E gene, ORF1ab gene, RdRp gene and N gene in the viral load of wastewater samples. In the present study, the untreated wastewater samples from the municipal WWTPs and hospital wastewater samples showed the presence of SARS-CoV-2 viral genome, which was correlated with the increased number of COVID-19 positive patients from the concerned areas, as per reported in the publically available health data. This is the first study that investigated the presence of SARS-CoV-2 viral genome in wastewater, at higher ambient temperature (above 40°C), further validating WBE as a potential tool in predicting and mitigating outbreaks.HighlightsThe study reports detection of SARS-CoV-2 in sewage in India.The presence of SARS-CoV-2 was confirmed by RT-PCR.The presence of viral genome was detected at high ambient temperatures of 40-45° C.Corroborates trends in the WWTPs showing viral genome with public health data.Treated effluent from WWTPs appears safe for reuse with low public health concern.Graphical Abstract

The requirement of large land area limits the adoption of constructed wetlands (CWs) in urban settings with limited land availability. The area calculations for CW design are commonly carried out following Kikuth approach where the removal rate constant (K) is derived from literature. Investigation of secondary data of 82 vertical flow CWs, performed in this study, yielded wide variations (0.0003 - 0.822 md

Aluminium salts are widely investigated for the coagulation process for removal of fluoride, but the residual Al above the acceptable limit is the main concern which is mainly due to the formation of soluble and colloidal Al-F complexes of aluminium and fluoride. Hence, it is necessary to investigate the nature and mechanism of formation of colloidal, dissolved and precipitated Al-F complexes and other Al associated species, that govern the concentration of residual Al in the defluoridated water. In the present study, experiments were performed to find the optimized dosage of aluminium sulfate (alum) and polyaluminium (PACl) for removal of fluoride from drinking water. Residual fluoride, turbidity and TDS were found to be 1.3 ppm, 7 NTU & 280 ppm respectively, for alum and 0.48 ppm, 4 NTU & 200 ppm respectively for PACl for initial fluoride concentration of 4 ppm. Residual Al was found to be above the acceptable limit (0.2 ppm), but it was less for PACl as compared to alum, however, after the subsequent microfiltration, residual Al was 0.268 & 0.13 for alum & PACl respectively that almost met the acceptable limit. Characterization of the treated water before and after filtration by using microfiltration membrane was done through electrospray ionization mass spectroscopy (ESI-MS) to identify the colloidal, dissolved Al-F species. Aluminium species in the form AlF52−,AlF2+, AlF4−, Al2(OH)22+, Al(OH)2+, Al(OH)2F2−, AlOHF+ etc. as Al-F were recognised. From the ESI-MS results, it was observed that only a few Al-F complexes with lesser concentrations were formed in case of PACl, which confirmed the fact that PACl worked better for the fluoride removal with low residual Al. The settling of the Al-F complexes for PACl was better than alum due to the difference in flocculation mechanism bridging in case of PACl and sweep flocculation for alum. XRD, SEM & FT-IR analysis of alum and PACl sludge was done to identify the precipitated species.

Wastewater-based surveillance has been emerging as an efficient and advantageous tool to predict COVID-19 prevalence in the population, much earlier (7–28 days) than reported clinical cases, thus providing sufficient time to organize resources and optimize their use in managing COVID-19. Since the commencement of the COVID-19 pandemic, SARS-CoV-2 genetic lineages have emerged and are circulating all over the world. The assessment of SARS-CoV-2 variants of concern (VOCs) in wastewater has recently been proven to be successful. The present research demonstrates a case study utilizing an established approach to perform monitoring of SARS-CoV-2 variants from 11 distinct wastewater treatment plants across Jaipur (India) during the second peak period of COVID-19 (from 19 February 2021 to 8 June 2021). The sequences obtained were analyzed to detect lineage using the Pangolin tool and SNPs using the mpileup utility of Samtools, which reported high genome coverage. The mutation analyses successfully identified the penetration of the B.1. in the first two weeks of sampling (19–26 February), followed by the B.1.617.2 variant into Jaipur in the first week of March 2021. B.1.617.2 was initially discovered in India in October 2020; however, it was not reported until early April 2021.The present study identified the presence of B.1.617.2 in early March, which correlates well with the clinical patient’s data (290 cases were reported much later by the government on 10 May 2021). The average total genome coverage of the samples is 94.39% when mapped onto the severe acute respiratory syndrome coronavirus 2 isolate Wuhan-Hu-1; a complete genome (NC_045512.2) sequence and SNP analysis showed that 37–51 SNPs were identified in each sample. The current study demonstrates that sewage surveillance for variant characterization is a reliable and practical method for tracking the diversity of SARS-CoV-2 strains in the community that is considerably faster than clinical genomic surveillance. As a result, this method can predict the advent of epidemiologically or clinically important mutations/variants, which can help with public health decision making.

Reverse osmosis is the paramount technology substantially contributing to meet the worldwide demand of drinking water with major challenge of reject disposal. Out of several RO reject treatment approaches, capacitive deionization can offer a viable alternative to treat concentrated streams, via application of small voltage (1.0 V) to the fabricated simple wire shaped electrodes coated with micro-porous material. Electrochemical analysis revealed a potentially high specific capacitance of 176.75F/g and a resistance of 4.87 Ω. Influence of initial concentration (500–2500 mg/L), electro sorption time (10–60 min), and stacking (1–5) of the electrodes was observed over the performance of the system to develop optimal parameters in a batch mode via Box-Behnken design. It was analysed that the fabricated electrodes possess maximum sorption capability of 35 mg/g fitting well with R2 value of 0.99 and second order rate kinetics was well fitted. The mechanism for the same was delineated highlighting electrostatic attractions. Moreover, the application of the system was explored by treating the reject from domestic RO systems and high TDS ground water samples. It was observed that monovalent ions had relatively lesser selectivity to the electrode surface as compared to the divalent ions.

Fluoride contamination of groundwater has become a major concern worldwide, resulting in serious medical conditions such as dental and skeletal fluorosis. Consequently, the WHO recommends that drinking water should not contain more than 1.5 mg/l of fluoride. Various defluoridation techniques such as coagulation, reverse osmosis, activated alumina adsorption, and biosorbent adsorption have been developed. Adsorption through the activated alumina and biosorbent process is not cost effective and has regeneration problems, and the reverse osmosis process has the high initial cost which makes it unacceptable for developing countries. Coagulation is a commonly employed field technology for defluoridation, which involves the addition of aluminum salts, lime, and bleaching powder followed by rapid mixing, flocculation, sedimentation, and filtration but suffers from a limitation of high residual aluminum in treated water. This paper critically reviews the recent developments in the coagulation technique for defluoridation along with its comparison to other defluoridation techniques. The review describes the pertinent gaps in the process and throws open suggestions for extending research by citing the recent studies which may lead to the revival of the process. The description about the suspension of alumino-fluoro complexes that constitute a substantial part of the residual aluminum after alum treatment has been narrated in the paper that helps in a deeper understanding of the defluoridation mechanism. To make the process highly suitable for communities, appropriate technological interventions, such as converting it to a continuous mode of operation, replacing alum with poly-aluminum chloride (PAC), and attaching a micro-filtration unit in series of the existing process, can be done. Also, using PAC as a coagulant with sand filtration has to be considered for making the process more efficient.

Chlorination has been employed extensively for sewage disinfection so that it can be reused, but the health issues related to its disinfection byproducts (DBPs) have forced to search for safer options. The present study focuses on the efficiency of chlorine disinfection on five dominant coliform bacterial species present in the secondary treated effluent. Resistance to low doses of chlorine was observed by few coliform species, such as Serratia/Hafnia which in turn required much higher doses of chlorine to achieve Total Coliform Count (TCC) within standards. This consequently increased formation of DBPs. A quadratic model of design of experiments (DOE) softaware was opted as an optimization strategy for chlorination, which was attempted to achieve counts for rest of the species to be brought within standard except for resistant ones so that the initial disinfection with chlorine could be terminated at this dose. This would then be followed by another disinfectant (UV/Ozone) against which such resistance among those species was not observed. The optimized results of chlorination (2.5 ppm of CD at 14.83 min/42 mg-min/L) would be useful in designing a hybrid disifection strategy which may help reduce the CD substantially and thereby its byproducts. Analysis of four Trihalomethanes (THMs) was carried out with the help of Gas chromatography-mass spectrometry and gas chromatography/tandem mass spectrometry (GC–MS/MS) to assess their concentrations due to chlorination of sewage. The effect of chlorine on physiology of bacterial cells was also examined through scanned electron microscopy (SEM) analysis to get a clue to inactivation mechanism.

The main aim of this article is to provide a state-of-the-art review of the experimental studies on vacuum membrane distillation (VMD) process. An introduction to the history of VMD is carried out along with the other membrane distillation configurations. Recent developments in process, characterization of membrane, module design, transport phenomena, and effect of operating parameters on permeate flux are discussed for VMD in detail. Several heat and mass transfer correlations obtained by various researchers for different VMD modules have been discussed. The impact of membrane fouling with its control in VMD is discussed in detail. In this paper, temperature polarization coefficient and concentration polarization coefficient are elaborated in detail. Integration of VMD with other membrane separation processes/industrial processes have been explained to improve the performance of the system and make it more energy efficient. A critical evaluation of the VMD literature is incorporated throughout this review.

Indiscriminate use of antibiotics in humans and animals and release of inadequately treated hospital, animal farming, and aquaculture wastewater into the domestic sewage have led to an increased concentration of antibiotics in the wastewater. In the presence of positive selection pressure due to subinhibitory concentration favoring antibiotic-resistant strains, wastewater treatment plants serve as a hotspot for rapid dissemination of antibiotic resistance genes in susceptible strains. The technologies used water treatment plants, especially the tertiary treatment, which may play a pivotal role in checking the release of antibiotics and antibiotic-resistant genes into the environment. Conventional treatments involving chlorination as well as advanced oxidation processes like ozonation, Fenton process, photo-Fenton process, and their combination with UV/H2O2 are being studied for degradation of various antibiotics during water treatment. Similarly, a large number of culture-based and metagenomics analyses have been carried out on the removal of antibiotic resistance genes in various pilot scale and field scale wastewater treatment systems. This chapter discusses the role of different tertiary treatments in handling antibiotics and antibiotic resistance genes in wastewater. The different types of tertiary treatment technologies are compared in terms of their efficiencies in dealing with these emerging pollutants so as to devise a treatment strategy that poses minimum threat to the ecosystem.

Generation of an excessive amount of sludge with various water treatment plants has become a major problem worldwide. Due to the scarcity of land and environmental concern, management of sludge is the prime concern nowadays. In fluoride removal process via coagulation, aluminium sulphate (alum) and poly aluminium chloride (PACl) are the chief coagulants, and the sludge is generated in massive amount from the defluoridation plants. Previous researchers pointed towards the health concerns related to its disposal. In Rajasthan state, India, Bisalpur dam supplies 16.2 TMC per day out of which 5.1 TMC is supplied to Ajmer district and 11.1 to Jaipur district. About 16.5 metric tonne sludge is generated per day which is a huge quantity. As aluminium sulphate is used as coagulant in water treatment plant, this sludge is highly toxic as it contains metals like aluminium, so its disposal is a major problem for Public Health Engineering Department (PHED). According to Central Pollution Control Board (CPCB), India, India is producing huge amount of inevitable waste everyday at their water treatment plants which requires proper handling and disposal. Therefore, there is an urgent need to look out for a proper management of the sludge. Moreover, the use of a large volume of sludge as a construction material can solve disposal problems and makes an approach towards eco-friendly construction. This paper presents an overview on the behaviour of cement mortars with different proportions of sludge. The compressive strength and microstructure analysis in comparison with the control mix are the vital factors for the cement mortars. The description about the performance of the both sludge: alum and PACl has been reviewed which suggests that PACl sludge is better in handling and does not have a negative effect on compressive strength of the mortars. However, alum sludge has sulphate content, and it retards the compressive strength of the mortars after certain proportion of sludge.

Management of bacterial survival post chlorine disinfection is vital for safe wastewater reuse for irrigation, as the presence of microorganisms in large numbers may lead to subsequent contamination of the surface and ground water reservoirs. Even after satisfying the current norms of coliform counts after disinfection (less than 1000 MPN per 100 mL), chlorine tolerant bacteria surviving in inadequately treated wastewater may pose a public health threat as many of these bacteria are able to re-grow upon storage. The current study is aimed to assess the magnitude of the problem posed by chlorine tolerant bacteria during chlorine disinfection and attempts to derive a strategy for safe disinfection. The chlorine tolerance was examined in the dominant gram negative bacteria (GNB) recovered from secondary treated sewage from a treatment plant located at Jaipur, India. Bacterial survival and re-growth (after 24 h) studies on test species (n = 11) with reference to E.coli ATCC 25922 reveal that, while the lethal doses of isolates ranged from 0.5 to 1.25 mgL−1,the chlorine doses for complete inhibition of re-growth were much higher (0.75–1.75 mgL−1).The isolates showing highest lethal dose and re-growth inhibition dose, identified as Citrobacter freundii, Klebsiella sp. and Stenotrophomonas maltophilia also exhibited very low log effective reduction (0.72–1.90) values and were selected as chlorine tolerant bacteria. Results of inactivation kinetics experiments on chlorine tolerant bacteria reveal a strong correlation (R2 > 0.89–0.99) between log reduction values and contact time. In re-growth kinetics experiments, maximum re-growth was observed after 6 h exposure following which, only marginal increase was registered up to 24 h. The study indicates that the existing approach of bacterial elimination post chlorine treatment may be grossly inadequate to assess the performance of the disinfection process adopted for drinking water treatment. It further brings out a novel approach to arrive at meaningful chlorine doses that take bacterial re-growth into account for achieving safe disinfection.

Globally estrogenic pollutants are a cause of concern in wastewaters and water bodies because of their high endocrine disrupting activity leading to extremely negative impacts on humans and other organisms even at very low environmental concentrations. Bioremediation of estrogens has been studied extensively and one technology that has emerged with its promising capabilities is Bioelectrochemical Systems (BESs). Several studies in the past have investigated BESs applications for treatment of wastewaters containing toxic recalcitrant pollutants with a primary focus on improvement of performance of these systems for their deployment in real field applications. But the information is scattered and further the improvements are difficult to achieve for standalone BESs. This review critically examines the various existing treatment technologies for the effective estrogen degradation. The major focus of this paper is on the technological advancements for scaling up of these BESs for the real field applications along with their integration with the existing and conventional wastewater treatment systems. A detailed discussion on few selected microbial species having the unusual properties of heterotrophic nitrification and extraordinary stress response ability to toxic compounds and their degradation has been highlighted. Based on the in-depth study and analysis of BESs, microbes and possible benefits of various treatment methods for estrogen removal, we have proposed a sustainable Hybrid BES-centered treatment system for this purpose as a choice for wastewater treatment. We have also identified three pipeline tasks that reflect the vital parts of the life cycle of drugs and integrated treatment unit, as a way forward to foster bioeconomy along with an approach for sustainable wastewater treatment.

Chlorine tolerance is a major concern during disinfection of treated wastewater. Here, the UV disinfection efficacy was assessed for controlling two previously reported chlorine tolerant bacteria, Stenotrophomonas maltophilia and Klebsiella sp. along with a standard E.coli strain using a collimated beam apparatus. UV exposure was applied in two sets - short exposure (0–60 s) and long exposure (0–60 min). Bacterial counts immediately after, and 24 h post irradiation (regrowth) were analysed using media plating. Morphological characteristics and intracellular Mn/Fe ratio were examined by SEM and ICP-OES respectively, to understand the possible reasons for sensitivity/ resistance to irradiation. E.coli and Klebsiella sp. were effectively reduced (> 4 log) but S. maltophilia showed low Effective Reduction (ER

Ozone is an attractive disinfection alternative to chlorine as chlorine has some environmental consequences due to its disinfection byproducts potential. In the present study ozone was used for the disinfection of secondary treated effluent of sewage treatment plant which is based on rotating biological contactor, process, Malaviya National Institute of Technology (Jaipur). From the experimental results it was found that ozone dose of 30 mg/L was required to achieve WHO standards for Total Coliform Count (TCC) of 1000 CFU/100 mL for food crop irrigation and recreational impoundments. One factorial design method of response surface methodology (RSM) was used for statistically obtaining optimum ozone dose that satisfies the norms for COD and TCC simultaneously. The optimized ozone dose suggested by the model was 30 mg/L to bring TCC within norms and the value of COD at this dose was 21 mg/L. Experimental verification of the results was in good agreement with the predicted results of one factorial design. Analysis of scanned electron microscopy (SEM) images, shows the effect of ozone doses on bacterial cell membrane. Effect of ozone on four trihalomethanes was also studied using GC–MS/MS.