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Dewatered sludges from twenty-two sewage treatment facilities were characterized to develop the quality control indices in India. This study used fertilizer index (FI) and clean index (CI) as a tool for categorizing sludge utilization into different classes (A, B, C and limited use classes LU-1, LU-2, LU-3) by their fertilizing potential, toxicity level, pathogen presence, and vector attraction reduction criteria. The findings revealed that total P (as P2O5), total N, and K (as K2O) in the sludge samples ranged from 0.9 to 5.7%, 1.2 to 3.8%, and 0.1 to 1.5%, respectively. Moreover, all sludges belong to Class C and lower category due to the presence of toxic metals and pathogens. The helminth eggs were found in the range of 25–1450 Numbers/4gTS in sludge samples. The highest number of helminth eggs of 1450/4 g of TS was found in the fecal sludge. The specific oxygen uptake rate (SOUR) values in the sludge samples varied from 0.3 to 4.9, with a median value of 1.3 and an RSD of 86% is way too high. It indicates that the sludge samples need further treatment to be less attractive as a food source for vectors and rodents. However, sludge samples have fertilizing potential and FI values ranges from 4.1 to 4.9, and CI value ranges from 2.5 to 5.0. It indicates that compost is best in quality and has high-fertilizer potential and low heavy-metal content, which is suitable for high-value crops such as organic farming. Further sludge treatment using typical composting, aerobic or anaerobic digestion, and solar or thermal drying could bring the sludges into the Class A and B categories. [ABSTRACT FROM AUTHOR]

The mitigation of sewage sludge is quite challenging, as the general method of disposal of sludge after being treated at the waste water treatment plant is landfilling, which makes land unfit for either agricultural or commercial growth. The disposal of sewage sludge in India presents significant environmental challenges due to increasing urbanization and limited land availability. Understanding the potential use of sewage sludge as a construction material has been verified to be the best method of recycling and environmental protection. The possible use of sewage sludge in civil engineering firms is discussed in this paper, along with the various testing methods. Carefully treated sewage sludge is proven to be an effective material, either as a replacement for cement or aggregates in construction. This paper indicates that sewage sludge can be effectively utilized as a raw material in concrete, contributing to resource conservation and environmental sustainability. It supports the feasibility of using sewage sludge in various construction applications, such as eco-cement, bricks, and lightweight aggregates, offering an eco-friendly solution to sewage sludge disposal. [ABSTRACT FROM AUTHOR]

The present study highlights the occurrence and the temporal variations of physicochemical properties, and heavy metals in the sludge from sewage treatment plants (STPs) located in industrial (two sites) and non-industrial (one site) cities of Haryana, India. The sludge was acidic (5.59) to neutral (7.21) with a mean EC of 7.4 dS m−1. Prominent heavy metals present in the sewage sludge from industrial sites were Cd, Ni, and Cr with maximum values of 2.83, 1449.0, and 3918.5 mg kg−1, respectively. The contamination and enrichment factor better explained the buildup of Ni, Cr, and Cu in the sewage sludge from industrial sites. The pH, total carbon, phosphorus, and other water–soluble anions, viz. SO42−, Cl−, HCO3−, and PO43−, were the most important attributes of sludge controlling the binding and removal of the metals with particulate matters during the phase separation in STPs. These attributes explained about 90% of the variation in Cd, Ni, Cr, Cu, Mn, and Zn content of the sludge from different STPs. Sludge from the non-industrial site had a low potential ecological risk index of 74.0 compared to a very high-risk index of 2186.5 associated with the industrial sites. This study concludes that besides the concentration of the heavy metals, the enrichment factor coupled with geo-accumulation or ecological risk index can effectively categorize the sludge. However, these indices need to be linked with bioaccumulation, bioaccessibility, and biomass quality under different agroecologies for guiding the safer use of sewage sludge in agriculture. [ABSTRACT FROM AUTHOR]

This article presents India's sanitation scenario, including the existing knowledge base in sewage and faecal sludge management, the status of reuse of sewage and current regulatory norms. The review indicated that changes in land use and socio-economic patterns over a period of time created greater pollution loads that could not be tackled with the regulatory norms prescribed by the Ministry of Environment, Forest and Climate Change in 2017. It was evident that under this notification, no emphasis was given for the removal of chemical oxygen demand, total nitrogen, total phosphorus and the faecal coliforms concentration was also relaxed. Subsequently, these standards were revised and applied by the Hon'ble National Green Tribunal in 2019, after including stringent values for chemical oxygen demand, total nitrogen, total phosphorus and the faecal coliforms; all across the country irrespective of the type of receiving environment. The review depicted that revisiting regulatory norms based on the type of "Receiving Environment" (Land/River/Lakes/Marine, etc.) is the need of the hour. The studies also suggested that it is necessary to devise end-use specific treated effluent reuse standards on similar lines of the World Health Organization/United States Environment Protection Agency. Finally, the authors suggest nationwide capacity building for sewage and faceal sludge treatment, up-grading existing sewage treatment plants, and propose revised regulatory norms based on the type of receiving environment to maintain a harmony between the economics of pollution control and improvement in the quality of water bodies across the country. [ABSTRACT FROM AUTHOR]

Sewage treatment plant (STP) acts as a potential source of microplastic contamination in the environment. The presence of microplastics in the sewage treatment plant is reported over the globe in varying concentrations. Hence, the current study is intended to evaluate the presence and abundance of microplastics occurring in sewage treatment plants in India. The samples were processed through digestion and density separation, followed by microscopic and polymer identification through Fourier transform infrared spectroscopy. Also, different wastewater parameters were studied to analyze their influence. High microplastic concentrations were detected in the influent (1860 ± 265 MPs/L), which reduced by > 90%, to around 148 ± 51 MPs/L in the effluent. The concentration of microplastics in sewage sludge was 830 MPs/kg. The prominent plastic types identified include low-density polyethylene, polypropylene, polyurethane, polyvinyl chloride, and rayon. The smaller particles prevail in the effluent, releasing around 30 billion particles per day to the environment. This suggests that the current STP is efficient in removing the majority of the particles, but considerations are needed to avoid the ecological risks associated. [ABSTRACT FROM AUTHOR]

This study characterises the sewage sludge from 26 sewage treatment plants in India, which demonstrates the nutrient potential and highlights the associated challenges in using the sludge. The dry sludge had 2.35%–4.2% N, 2.46–3.2% phosphorus (P2O5) and 0.83%–1.24% potassium oxide (K2O), whereas sludge ash contains ~13.6% and 2.7%, P2O5 and K2O, respectively. Total nutrient potential from the sludge of the existing sewage treatment facility was 97.5 × 103 tonne/year, which is equivalent to 0.92% urea or 0.19% NPK used presently as conventional fertilisers in India. However, pre‐treatment may be required for this sludge before using it in agricultural fields as heavy metals, such as Zn, Cu, Ni, Cd, and Cr, were found higher than the compost standards. This study would be useful for the researchers and policymakers globally and would motivate them to make policies and deploy suitable technologies towards the nutrient utilisation from sewage sludge. [ABSTRACT FROM AUTHOR]

This study investigates the occurrence and characterization of microplastic (MP) in sewage sludge from 3 different cities along the Ganga River, India and their toxic impact while applying sludge for crop production. MP occurred in the ranges of 29.2–60.8 × 103 particles kg−1 with an abundance of 1–5 mm (11.12%), <1 mm–100 μm (32.65%), and 20–100 μm (56.23%) size particles. ATR-FTIR analysis suggested polypropylene, polyethylene, nylon, and polycarbonate as sludge's most common MP polymer. In lab scale trials, sludge MP showed significant toxicity in Vigna radiata and reduced vegetative growth and plant weight was recorded with sludge-inoculated setups. Seedlings with sludge exhibited higher activities of catalase, superoxide dismutase, hydrogen peroxide (H 2 O 2), and malondialdehyde than the control setups. Furthermore, fluorescence microscopy confirmed the MP bioaccumulation in tested seedlings. In summary, our results suggested that wastewater treatment plants (WWTPs) sink large volumes of MP in sewage sludge, which could be hazardous while applying such biosolids for crop production. MP seasonal dynamics in local WWTPs and their role in the mobilization of other toxicant chemicals could be investigated in future studies in this series. [Display omitted] • MP load in sewage sludge ranged between 29.2 and 60.8 × 103 particles/kg. • MP-sized 20–100 μm were higher in sludge. • The plant grown in sludge showed low growth but high oxidative stress. • Fluorescence microscopy confirms the MP accumulation in seedling roots. [ABSTRACT FROM AUTHOR]

Sewage treatment plants (STPs) as a carrier of microplastics (MPs) have received considerable attention worldwide recently. In India, the majority of studies on MPs have been conducted in sediments, riverine, and marine systems, while knowledge on MPs occurrence in STPs is scarce. Henceforth, this work evaluated the presence of MPs in sewage and sludge in a hybrid growth, secondary treatment-based STP system. Optical microscopy, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy methods were used to examine the abundance of MPs in raw sewage, effluent from different treatment units of the STP, and sludge samples. A total number of MPs of 201 ± 19 (2021) and 197 ± 22 (2022) were detected in the studied STP system. Results showed that MPs ranged between 64.3 ± 4.89–47.66 ± 4.71 n/L (sewage) and 1.14 ± 0.30–1.38 ± 0.65 n/g (sludge) with the overall removal efficacy of the studied STP estimated to be around 80%. Fragments and fibers were predominant among all shapes and particles mostly belonged to sizes <50 μm and <50 μm–250 μm in sewage and sludge, respectively. In total, seven polymers were identified of which low-density polyethylene (LDPE) constituted the highest proportion in sewage (26%–31%) and polyvinyl chloride (PVC) contributed the highest in the sludge (22%–27%). Moreover, MPs control measures have been discussed based on the findings of this study to restrict MPs re-entry into the environment via treated effluent and sludge. [Display omitted] • First study on MPs occurrence and removal in a hybrid growth MBBR-based STP. • Around 80% MPs were removed via the primary and secondary treatment stages in the STP. • LDPE (in sewage) and PVC (in sludge) were the most prevalent polymers. • Small-sized MPs (<250 μm) like fragments and fibers were predominant shapes. • Advanced treatment options for MPs removal from secondary-treated effluent discussed. [ABSTRACT FROM AUTHOR]

The objective of this work was to develop a relationship between odour intensity and sewage concentration by using data collected from various sensitive areas of an activated sludge based sewage treatment plant at Titagarh, near Kolkata, India. A number of well-known psychophysical models (e.g., Weber--Fechner law, Steven's power law, Beidler's and Laffort's models) that can successfully relate the perceived intensity with the sewage concentration have been discussed. Respective parameters for each of the models were estimated by the nonlinear Levenburg--Marquardt parameter estimation method. The overall performance of the model was tested statistically against sets of data from the panel method analysis. The model based on the Weber--Fechner law was ranked 1 in the case of three out of eight samples and it was found more representative of the more intense odour samples. The model based on power law equation represented the intensity-concentration relationship better with extremely low uncertainties on both parameters k1 and k2 for comparatively less intense odour samples. Only 1 sample out of the 8 samples based on Beidler's model was found more representative for the high intense sewage samples. [ABSTRACT FROM AUTHOR]

This paper presents results of a novel application of coupling the Activated Sludge Model No. 3 (ASM3) and the Anaerobic Digestion Model No.1 (ADM1) to assess a tropical wastewater treatment plant in a developing country (Surat, India). In general, the coupled model was very capable of predicting current plant operation. The model proved to be a useful tool in investigating various scenarios for optimising treatment performance under present conditions and examination of upgrade options to meet stricter and upcoming effluent discharge criteria regarding N removal. It appears that use of plant-wide modelling of wastewater treatment plants is a promising approach towards addressing often complex interactions within the plant itself. It can also create an enabling environment for the implementations of the novel side processes for treatment of nutrient-rich, side-streams (reject water) from sludge treatment. [ABSTRACT FROM AUTHOR]

Sewage sludge, generated post wastewater treatment, constitutes only a small percentage of the total amount of sewage treated, however, its sustainable management is inevitable. In this study, the energy recovery potential of sewage sludge by incineration and anaerobic digestion is investigated for India. The dewatered sludge has total solid content of 25–45% whereas, the primary characteristics of sewage sludge showed significant organic content of about ∼23–40% (dry basis). The calorific value was found to be 8–21 MJ/kg for sludge dry matter. The energy recovery potential of sewage sludge was 555–1068 kWh/tonne on sludge dry matter basis for incineration and 315–608 kWh/tonne for anaerobic digestion. Additionally, the energy recovery potential of current sewage treatment in India was found to be ∼15.3 × 105 or 8.6 × 105 MWh, annually for incineration and anaerobic digestion, respectively. The study had provided in depth view of sludge to be considered as energetic material and its energy recovery potential countrywide, which would not only help for give a proper direction for recovering energy but also helpful to deal with the issue of sludge management in India. Image 1 • Sludge generated from sewage treatment plants was explored for energy alternatives. • The sewage sludge contains high heating value, organic matter and volatile matter etc. • Energy recovery potential of sewage sludge produced in India was estimated. • The energy recovery from sewage sludge could reduce energy demands and reduce land requirement for its disposal as well. [ABSTRACT FROM AUTHOR]