Treatment of clinical laboratory sewage using a decentralized treatment unit and risk reduction for its reuse in irrigation using hybrid disinfection.

The disinfection efficacy of standalone chlorine, UV and their combined approach (hybrid) was investigated for the coliform removal in BioKube 1 and 2 treated effluents collected from different environmental settings of clinical and domestic wastes. Chlorine and UV disinfection were applied to BioKube treated wastewater with doses from 0 to 4 mg L-1 and 0-166 mJ cm-2 respectively. Combined disinfection strategies were designed to reduce the dose of chlorine and UV and to exploit the synergistic effect of them. The culturable coliforms were enumerated in treated wastewater sample (control), immediately after (reduction), and 24 h post disinfections (regrowth) using culture media plating and colilert-18 media. Both the BioKube systems (1 and 2) were effective in achieving the strict norms of physicochemical parameters, but not following the coliform counts of treated effluent for reuse in irrigation. A hybrid strategy of chlorine followed by UV was found to be the most effective among various standalone and combination approaches for the removal of coliforms (>4 log ER or <1000 CFU/100 mL) from both the treated effluents. However, coliform present in treated effluent of BioKube 1 were resisting (regrowth) against all kind of applied disinfectants except chlorine followed by UV dose at or more than 0.5 mg L-1 + 41 mJ cm-2. Limited reports are available on hybrid disinfection approaches with decentralized packaged sewage treatment units and this study would help to adopt as an effective tertiary treatment strategy for reuse of treated sewage for irrigation while ensuring public health safety.

Optimization of depth of filler media in horizontal flow constructed wetlands for maximizing removal rate coefficients of targeted pollutant(s).

Varying the depth of HFCW media causes differences in the redox status within the system, and hence the community structure and diversity of bacteria, affecting removal rates of different pollutants. The key functional microorganisms of CWs that remove contaminants belong to the phyla Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes. Secondary data of 111 HFCWs (1232 datasets) were analyzed to deduce the relationship between volumetric removal rate coefficients (KBOD, KTN, KTKN, and KTP) and depth. Equations of depth were derived in terms of rate coefficients using machine learning approach (MLR and SVR) (R2 = 0.85, 0.87 respectively). These equations were then used to find the optimum depth for pollutant(s) removal using Grey wolf optimization (GWO). The computed optimum depths were 1.48, 1.71, 1.91, 2.09, and 2.14 m for the removal of BOD, TKN, TN, TP, and combined nutrients, respectively, which were validated through primary data. This study would be helpful for optimal design of HFCWs.

Antibiotic resistance genes and bacterial diversity: A comparative molecular study of treated sewage from different origins and their impact on irrigated soils.

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, ß-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.

A systematic review on chlorine tolerance among bacteria and standardization of their assessment protocol in wastewater.

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.

Designing the vertical flow constructed wetland based on targeted limiting pollutant.

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-1) in the calculated K values for different pollutants under different environmental and operational conditions indicating that it is important to incorporate the desired levels of pollutant removal to arrive at customized design of CWs. The results indicated that the relative standard deviation of K values could be narrowed by classifying the datasets based on design parameters like depth, hydraulic loading rates and substrate loading rates. These calculations can help arrive at more scientific design of CW to achieve the prevailing standards for the discharge or reuse of sewage.

Metagenomic Survey Reveals More Diverse and Abundant Antibiotic Resistance Genes in Municipal Wastewater Than Hospital Wastewater.

Alongside antibiotic resistance, co-selection of antibiotics, biocides, and metal resistance is a growing concern. While hospital wastewater is considered a hotspot for antibiotic-resistant bacteria (ARB) and genes (ARGs), the scenario in India, one of the biggest consumers of antibiotics, remains poorly described. In this study, we used metagenomic sequencing to characterize ARGs and biocide/metal resistance genes (BMRGs) in four wastewater treatment plants (WWTPs) in Jaipur City of India. We observed a significantly lower richness and abundance of ARGs in the influent of a WWTP exclusively receiving hospital wastewater when compared to other three WWTPs involving municipal wastewater treatment. Several tetracycline and macrolide-lincosamide-streptogramin resistance genes were enriched in influents of these three municipal wastewater-related treatment plants, whereas hospital wastewater had a higher abundance of genes conferring resistance to disinfectant-related compounds such as synergize and wex-cide-128, reflecting the patterns of antibiotic/disinfectant use. Of note, in the wastewater system with more chemicals, there was a strong correlation between the numbers of ARGs and BMRGs potentially harbored by common hosts. Our study highlights significant influxes of ARGs from non-hospital sources in Jaipur City, and thus more attention should be paid on the emergence of ARGs in general communities.

Impact of combined chlorine and UV technology on the bacterial diversity, antibiotic resistance genes and disinfection by-products in treated sewage.

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.

Bioelectrochemical systems for environmental remediation of estrogens: A review and way forward.

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.

Performance assessment of pulsating floc blanket clarifiers and conventional clariflocculators in pilot-scale models.

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.

Nitrogen transformation processes and mass balance in deep constructed wetlands treating sewage, exploring the anammox contribution.

This work was aimed to assess the contribution of classical nitrogen removal pathways in two deep constructed wetlands CW1 and CW2 located at Jaipur, India. Nitrogen mass balance revealed that 44.87% and 43.77% losses of T-N in CW1 and CW2 were unaccounted for. To elucidate these significant losses, the study was extended to assess the occurrence and contribution of a novel pathway (ANAMMOX) in overall nitrogen removal. The ratio of NH4+-N (removed) & NO3--N (produced) in CW1 & CW2 indicated that ANAMMOX could be one of the key pathways for nitrogen removal in the CWs besides nitrification-denitrification in microbial films. The molecular analysis confirmed bands of ANAMMOX bacteria developed intrinsically. The study revealed that deep wetlands can offer a feasible option for the sustenance of ANAMMOX bacteria and may help develop design parameters for CWs for achieving higherT-N removal withsimilarsurface area as that of conventional wetlands.

Investigation of chlorine tolerance profile of dominant gram negative bacteria recovered from secondary treated wastewater in Jaipur, India.

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.

Development of a noise prediction model under interrupted traffic flow conditions: a case study for Jaipur city.

The objective of this study is to develop an empirical noise prediction model for the evaluation of equivalent noise levels (Leq) under interrupted traffic flow conditions. A new factor tendency to blow horn (AH) was introduced in the conventional federal highway administrative noise prediction (FHWA) model and a comparative study was made between FHWA and modified FHWA models to evaluate the best suitability of the model. Monitoring and modeling of Leq were carried out at four selected intersections of Jaipur city. After comparison of the results, it was found that the modified FHWA model could be satisfactorily applied for Indian conditions as it gives acceptable results with a deviation of +/-3 dB (A). In addition, statistical analysis of the data comprising measured and estimated values shows a good agreement. Hence, the modified FHWA traffic noise prediction model can be applied to the cities having similar traffic conditions as in Jaipur city.

Suspended particulate matter distribution in rural-industrial Satna and in urban-industrial South Delhi.

An air quality sampling program was designed and implemented to collect the baseline concentrations of respirable suspended particulates (RSP = PM10), non-respirable suspended particulates (NRSP) and fine suspended particulates (FSP = PM2.5). Over a three-week period, a 24-h average concentrations were calculated from the samples collected at an industrial site in Southern Delhi and compared to datasets collected in Satna by Envirotech Limited, Okhla, Delhi in order to establish the characteristic difference in emission patterns. PM2.5, PM10, and total suspended particulates (TSP) concentrations at Satna were 20.5 +/- 6.0, 102.1 +/- 41.1, and 387.6 +/- 222.4 microg m(-3) and at Delhi were 126.7 +/- 28.6, 268.6 +/- 39.1, and 687.7 +/- 117.4 microg m(-3). Values at Delhi were well above the standard limit for 24-h PM2.5 United States National Ambient Air Quality Standards (USNAAQS; 65 microg m(-3)), while values at Satna were under the standard limit. Results were compared with various worldwide studies. These comparisons suggest an immediate need for the promulgation of new PM2.5 standards. The position of PM10 in Delhi is drastic and needs an immediate attention. PM10 levels at Delhi were also well above the standard limit for 24-h PM10 National Ambient Air Quality Standards (NAAQS; 150 microg m(-3)), while levels at Satna remained under the standard limit. PM2.5/PM10 values were also calculated to determine PM2.5 contribution. At Satna, PM2.5 contribution to PM10 was only 20% compared to 47% in Delhi. TSP values at Delhi were well above, while TSP values at Satna were under, the standard limit for 24-h TSP NAAQS (500 microg m(-3)). At Satna, the PM10 contribution to TSP was only 26% compared to 39% in Delhi. The correlation between PM10, PM2.5, and TSP were also calculated in order to gain an insight to their sources. Both in Satna and in Delhi, none of the sources was dominant a varied pattern of emissions was obtained, showing the presence of heterogeneous emission density and that nonrespirable suspended particulate (NRSP) formed the greatest part of the particulate load.