Luffa cylindrica (Sponge Gourd) Fibers in Treatment of Greywater: an Aerobic Fixed-Film Reactor Approach.

The need for potable water consumption in urban and suburban regions can be decreased by greywater treatment and its reuse. Utilizing natural fibers may provide sustainable solutions in addressing challenges related to water resource management. In this study, a fixed-film reactor was designed with Luffa cylindrica (an annually occurring fruit) as a bio-carrier. The lab-scale reactors were configured with and without Luffa cylindrica and were run for 90 days in fed-batch mode. Scanning electron microscopy (SEM) was performed to validate biofilm production over time. Monitoring COD, nitrogen, and total phosphate removal allowed for analysis of treatment effectiveness. Results demonstrated the treatment efficiency for the experimental reactor was 70.96%, 97.02%, 92.57%, and 81.20% for COD, nitrogen, phosphate, and anionic surfactant (AS), respectively. 16 s rRNA gene sequencing of bio-carrier and control greywater samples was carried out. Many bacteria known to break down anionic surfactants were observed, and microbial succession was witnessed in the control reactor vs. the experimental reactor samples. The three most prevalent genera in the experimental samples were Chlorobium, Chlorobaculum, and Terrimonas. However, it is crucial to underscore that additional research is essential to solidify our understanding in this domain, with this study laying the fundamental groundwork.

Investigating the effects of irrigation with indirectly recharged groundwater using recycled water on soil and crops in semi-arid areas.

The utilization of direct wastewater for irrigation poses many environmental problems such as soil quality deterioration due to the accumulation of salts, heavy metals, micro-pollutants, and health risks due to undesirable microorganisms. This hampers its agricultural reuse in arid and semi-arid regions. To address these concerns, the present study introduces a recent approach that involves using indirectly recharged groundwater (GW) with secondary treated municipal wastewater (STW) for irrigation through a Soil Aquifer Treatment-based system (SAT). This method aims to mitigate freshwater scarcity in semi-arid regions. The study assessed GW levels, physicochemical properties, and microbial diversity of GW, and soil in both impacted (receiving recycled water) and non-impacted (not receiving recycled water) areas, before recycling (2015-2018) and after recycling (2019-2022) period of the project. The results indicated a significant increase of 68-70% in GW levels of the studied boreholes in the impacted areas. Additionally, the quality of indirectly recharged GW in the impacted areas improved notably in terms of electrical conductivity (EC), hardness, total dissolved solids (TDS), sodium adsorption ratio (SAR), along with certain cations and anions (hard water to soft water). No significant difference was observed in soil properties and microbial diversity of the impacted areas, except for EC and SAR, which were reduced by 50% and 39%, respectively, after the project commenced. The study also monitored specific microbial species, including total coliforms, Escherichia coli (as indicator organisms), Shigella, and Klebsiella in some of the harvested crops (beetroot, tomato, and spinach). However, none of the analysed crops exhibited the presence of the studied microorganisms. Overall, the study concludes that indirectly recharged GW using STW is a better sustainable and safe irrigation alternative compared to direct wastewater use or extracted hard GW from deep aquifers.

Assessing groundwater recharge rates, water quality changes, and agricultural impacts of large-scale water recycling.

The over-exploitation and insufficient replenishment of groundwater (GW) have resulted in a pressing need to conserve freshwater and reuse of treated wastewater. To address this issue, the Government of Karnataka launched a large-scale recycling (440 million liters/day) scheme to indirectly recharge GW using secondary treated municipal wastewater (STW) in drought-prone areas of Kolar district in southern India. This recycling employs soil aquifer treatment (SAT) technology, which involves filling surface run-off tanks with STW that intentionally infiltrate and recharge aquifers. This study quantifies the impact of STW recycling on GW recharge rates, levels, and quality in the crystalline aquifers of peninsular India. The study area is characterized by hard rock aquifers with fractured gneiss, granites, schists, and highly fractured weathered rocks. The agricultural impacts of the improved GW table are also quantified by comparing areas receiving STW to those not receiving it, and changes before and after STW recycling were measured. The AMBHAS_1D model was used to estimate the recharge rates and showed a tenfold increase in daily recharge rates, resulting in a significant increase in the GW levels. The results indicate that the surface water in the rejuvenated tanks meets the country's stringent water discharge standards for STW. The GW levels of the studied boreholes increased by 58-73 %, and the GW quality improved significantly, turning hard water into soft water. Land use land cover studies confirmed an increase in the number of water bodies, trees, and cultivated land. The availability of GW significantly improved agricultural productivity (11-42 %), milk productivity (33 %), and fish productivity (341 %). The study's outcomes are expected to serve as a role model for the rest of Indian metro cities and demonstrate the potential of reusing STW to achieve a circular economy and a water-resilient system.

Socio-economic impact assessment of large-scale recycling of treated municipal wastewater for indirect groundwater recharge.

Reusing treated wastewater is an emerging solution to address freshwater scarcity, and surface water contamination faced worldwide. A unique large-scale wastewater recycling project was implemented to replenish groundwater by filling secondary treated wastewater (STW) into existing irrigation tanks in severely drought-hit areas of the Kolar districts of Southern India. This study quantifies the socio-economic impacts of this large-scale indirect groundwater recharge scheme. The changes in areas receiving STW i.e., impacted areas and those areas which did not receive STW i.e., non-impacted areas was studied. Also, pre and post recycling changes were quantified in the Kolar district. The results show that surface water quality meets India's most stringent treated wastewater discharge standards prescribed by the Hon'ble National Green Tribunal. Due to these recycling efforts, significant improvements in groundwater level and quality were found. It was observed that there was a noticeable difference in agricultural cropping areas, seasons, patterns, and production between impacted and non-impacted areas. Post-recycling, farmers tended to cultivate cash and water-intensive crops over less water-intensive crops. During the post-recycling period, livestock and milk production also increased, and in impacted areas, it was significantly higher. Post-recycling, fish production increased and land prices per hectare increased by 118 % in impacted areas. The farmer's net income under flowers and vegetable farming increased by 202 % and 150 % respectively in impacted areas compared to non-impacted areas. Furthermore, this project contributes to a circular economy transition in the water sector, which has economic, environmental, social, and cultural benefits. A key recommendation from the outcomes of the study is to draft and implement a policy that encourages the reuse of recycled water for groundwater recharge which in turn will improve the agro-economic system and food security.

Study towards understanding foaming and foam stability in urban lakes.

Foaming water bodies have become a matter of great concern globally. Foam disrupts aquatic ecosystems, emits an offensive smell, disrupts the day-to-day activities in neighbouring localities, and is visually unpleasant. The downstream water bodies are also exposed to the risk of foaming. Even though widespread, the foaming phenomena of surface water bodies are not adequately studied. The present study focuses on the foaming Lake of Bellandur in South India - wherein the sources and concentration of surfactants, effect of phosphorous, effect of bacteria, and its synergy with surfactants were studied. The study revealed that the significant source of pollution in the Lake was the entry of untreated sewage, which consisted of surfactants. The anionic surfactant concentration in the Lake was 17 ± 3 ppm, and surface tension remained around 50 mN/m, similar to the treatment plant inlet. The Phosphorus concentration in the Lake was high at 10 ± 3 ppm, with the primary source being feces and urine. Phosphorus indirectly affected the surfactant concentration of the Lake. Foam stability studies showed that mixed bacteria (filamentous) from Bellandur, in its stationary phase-played a crucial role in adding to the stability of the foam. The highest contributing filamentous bacterial family was found to be Flavobacteriia.

Review on solid-state anaerobic digestion of lignocellulosic biomass and organic solid waste.

Sustainable management of organic solid wastes especially the municipal solid waste (MSW) is essential for the realization of various sustainable development goals (SDGs). Resource recovery centric waste processing technologies generate valorizable products to meet the operations and maintenance (O&M) costs while reducing the GHG emissions. Solid-state anaerobic digestion (SSAD) of organic solid wastes is a biomethanation process performed at a relatively higher total solids (TS) loading in the range of 10-45%. SSAD overcomes various limitations posed by conventional anaerobic slurry digesters such as higher degradable matter per unit volume of the bioreactor resulting in a smaller footprint, low freshwater consumption, low wastewater generation, simple upstream and downstream processes, relatively lower operation, and maintenance costs. This review elucidates the recent developments and critical assessment of different aspects of SSAD, such as bioreactor design, operational strategy, process performances, mass balance, microbial ecology, applications, and mathematical models. A critical assessment revealed that the operating scale of SSAD varies between 1000 and 100,000 ts/year at organic loading rate (OLR) of 2-15 g volatile solids (VS)/L·day. The SSAD experiences process failures due to the formation of volatile fatty acids (VFAs), biogas pockets and clogging of the digestate outlet. Acclimatization of microbes accelerates the startup phase, steady-state performances, and the enrichment of syntrophic microbes with 10-50 times greater population of cellulolytic and xylanolytic microbes in thermophilic SSAD over mesophilic SSAD. Experimental limitations in the accurate determination of rate constants and the oversimplification of biochemical reactions result in an inaccurate prediction by the models.

Household discharge of chemical products and its classification based on anaerobic biodegradability.

Synthetic household chemical products (HCP) are used in various household activities. An average urban household was estimated to consume ~ 3 kg HCP per month while discarding 212-387 mg/L HCP in sewage comprising > 265 different chemical compounds. The high sorption properties of HCP and their antimicrobial resistance lead to their long-term persistence in the environment. The intrusion of HCPs and their breakdown products into food chain causes detrimental effects on health and ecology. HCPs comprise mostly of a mixture of xenobiotics, organic and inorganic compounds resulting in an impaired biodegradation. Yet, the biodegradability of HCPs is seldom assessed. Therefore, this research proposes a modified Gompertz model approach to analyze BMP data in order to classify commercially available HCPs into seven groups based on the observed levels of recalcitrance and is in turn coined "Anaerobic Biodegradability Index" (ABI, beginning from ABI-VI to ABI-0 wherein ABI-VI represents the highest degradability and ABI-0 the least). This approach emulates "Energy-Star" ratings of electrical appliances classified based on electrical efficiency. Results of such a classification indicated that HCPs containing ≥ 10% anionic surfactants such as laundry detergents, handwash gel, dishwasher chemicals, and creosote surface cleaner, exhibit lowered anaerobic degradability and were therefore categorized between ABI-0 and ABI-II. Whereas the highly degradable HCP such as toothpaste, shower gel, and hair shampoo were categorized in ABI-V and ABI-VI categories. We perceive that the weightages and concentrations can be used in the future to define the capability of various wastewater treatment systems and their tolerance to various ABI classes.

Accumulation of antibiotic-resistant genes in anaerobic biofilm reactor fed with household chemical products.

This research aims to determine the presence of antibiotic-resistant genes (ARG) in anaerobic biofilm reactors (ABR) fed with household chemical products (HCP) such as laundry detergents and handwash without any influx of antibiotics. The ABR comprised a three-chamber design with bottom sludge, a middle chamber containing fluidized PVC spiral, and a top chamber with packed coir fiber as a biofilm support medium, respectively. Four different ABRs were simultaneously operated for a prolonged period (200 day) and subjected to variations in physicochemical conditions. The ABRs fed with HCP exhibited solitary accumulation of log (4.4-7.5) ermC gene copies/g VS whereas, ARG was undetectable in glucose fed ABRs indicating that HCP exhibited antimicrobial activities synonyms to Erythromycin. Accumulation of Erythromycin-C (ermC) was relatively higher on the biofilm inhabiting PVC support medium and further accentuated by effluent recycling to log 7.5 ermC gene copies at a ratio of ermC/16S gene copies of 0.65. Physico-chemical factors such as substrate composition, biofilm support medium, and effluent recycling simultaneously elevated the concentration of ermC genes. The results indicated that HCP augments the accumulation of ARG in the microbiome, subsequently, increasing the risk in ARG transmission from sewage treatment plants to the ecology and humans.

Investigations into the performance of single chamber sanitary napkin incinerators with emphasis on CO and CO2 emissions.

This paper investigates the performance of two commercially available sanitary napkin incinerators. On detailed preliminary investigations both the incinerators were found to have shortcomings to meet emission norms as per Indian standards for MSW incinerators. Parameters for the comparison were combustion efficiency and emissions, basically CO and CO2, to assess the quality of combustion. Carefully designed experiments, to improve the performance, revealed the need to evaluate the stochiometric air flow requirement and a need to modify. To enable better combustion inside the combustion chamber, it was established that airflow distribution, and mixing was necessary. The paper analyses the performance of the incinerators towards optimizing the air flow location and the air flow rate in the combustion chamber. Based on these studies it was evident that the commercially available designs are not suitable for five-napkin batches, as claimed by the manufacturers. A higher starting temperature (>600 °C) is essential for quick heating, and optimum an air supply (~10 LPM) is necessary for reducing environmentally sensitive emissions. Results indicated higher combustion efficiency, and a need for meeting the emissions norms as per Indian standards for MSW incinerators. Based on the performance of the devices and arriving at an optimal specification for the design, an alternative method of incineration using LPG gas torch retrofitted over the grate, was tested. The paper also discusses the preliminary results from the new design. The conducive environment in the combustion chamber resulted in higher combustion efficiencies and emissions which conform to Indian emission standards.

The physicochemical characteristics and anaerobic degradability of desiccated coconut industry waste water.

Desiccated coconut industries (DCI) create various intermediates from fresh coconut kernel for cosmetic, pharmaceutical and food industries. The mechanized and non-mechanized DCI process between 10,000 and 100,000 nuts/day to discharge 6-150 m(3) of malodorous waste water leading to a discharge of 264-6642 kg chemical oxygen demand (COD) daily. In these units, three main types of waste water streams are coconut kernel water, kernel wash water and virgin oil waste water. The effluent streams contain lipids (1-55 g/l), suspended solids (6-80 g/l) and volatile fatty acids (VFA) at concentrations that are inhibitory to anaerobic bacteria. Coconut water contributes to 20-50% of the total volume and 50-60% of the total organic loads and causes higher inhibition of anaerobic bacteria with an initial lag phase of 30 days. The lagooning method of treatment widely adopted failed to appreciably treat the waste water and often led to the accumulation of volatile fatty acids (propionic acid) along with long-chain unsaturated free fatty acids. Biogas generation during biological methane potential (BMP) assay required a 15-day adaptation time, and gas production occurred at low concentrations of coconut water while the other two streams did not appear to be inhibitory. The anaerobic bacteria can mineralize coconut lipids at concentrations of 175 mg/l; however; they are severely inhibited at a lipid level of ≥350 mg/g bacterial inoculum. The modified Gompertz model showed a good fit with the BMP data with a simple sigmoid pattern. However, it failed to fit experimental BMP data either possessing a longer lag phase and/or diauxic biogas production suggesting inhibition of anaerobic bacteria.

Bioremediation and lipid synthesis through mixotrophic algal consortia in municipal wastewater.

Algae grown in outdoor reactors (volume: 10 L and depth: 20 cm) were fed directly with filtered and sterilised municipal wastewater. The nutrient removal efficiencies were 86%, 90%, 89%, 70% and 76% for TOC, TN, NH4-N, TP and OP, respectively, and lipid content varied from 18% to 28.5% of dry algal biomass. Biomass productivity of ∼122 mg/l/d (surface productivity 24.4 g/m(2)/d) and lipid productivity of ∼32 mg/l/d were recorded. Gas chromatography and mass spectrometry (GC-MS) analyses of the fatty acid methyl esters (FAME) showed a higher content of desirable fatty acids (bearing biofuel properties) with major contributions from saturates such as palmitic acid [C16:0; ∼40%] and stearic acid [C18:0; ∼34%], followed by unsaturates such as oleic acid [C18:1(9); ∼10%] and linoleic acid [C18:2(9,12); ∼5%]. The decomposition of algal biomass and reactor residues with an exothermic heat content of 123.4 J/g provides the scope for further energy derivation.

Treatment efficacy of algae-based sewage treatment plants.

Lagoons have been traditionally used in India for decentralized treatment of domestic sewage. These are cost effective as they depend mainly on natural processes without any external energy inputs. This study focuses on the treatment efficiency of algae-based sewage treatment plant (STP) of 67.65 million liters per day (MLD) capacity considering the characteristics of domestic wastewater (sewage) and functioning of the treatment plant, while attempting to understand the role of algae in the treatment. STP performance was assessed by diurnal as well as periodic investigations of key water quality parameters and algal biota. STP with a residence time of 14.3 days perform moderately, which is evident from the removal of total chemical oxygen demand (COD) (60 %), filterable COD (50 %), total biochemical oxygen demand (BOD) (82 %), and filterable BOD (70 %) as sewage travels from the inlet to the outlet. Furthermore, nitrogen content showed sharp variations with total Kjeldahl nitrogen (TKN) removal of 36 %; ammonium N (NH4-N) removal efficiency of 18 %, nitrate (NO3-N) removal efficiency of 22 %, and nitrite (NO2-N) removal efficiency of 57.8 %. The predominant algae are euglenoides (in facultative lagoons) and chlorophycean members (maturation ponds). The drastic decrease of particulates and suspended matter highlights heterotrophy of euglenoides in removing particulates.

Micro-scale anaerobic digestion of point source components of organic fraction of municipal solid waste.

The fermentation characteristics of six specific types of the organic fraction of municipal solid waste (OFMSW) were examined, with an emphasis on properties that are needed when designing plug-flow type anaerobic bioreactors. More specifically, the decomposition patterns of a vegetable (cabbage), fruits (banana and citrus peels), fresh leaf litter of bamboo and teak leaves, and paper (newsprint) waste streams as feedstocks were studied. Individual OFMSW components were placed into nylon mesh bags and subjected to various fermentation periods (solids retention time, SRT) within the inlet of a functioning plug-flow biogas fermentor. These were removed at periodic intervals, and their composition was analyzed to monitor decomposition rates and changes in chemical composition. Components like cabbage waste, banana peels, and orange peels fermented rapidly both in a plug-flow biogas reactor (PFBR) as well as under a biological methane potential (BMP) assay, while other OFMSW components (leaf litter from bamboo and teak leaves and newsprint) fermented slowly with poor process stability and moderate biodegradation. For fruit and vegetable wastes (FVW), a rapid and efficient removal of pectins is the main cause of rapid disintegration of these feedstocks, which left behind very little compost forming residues (2-5%). Teak and bamboo leaves and newsprint decomposed only to 25-50% in 30d. These results confirm the potential for volatile fatty acids accumulation in a PFBR's inlet and suggest a modification of the inlet zone or operation of a PFBR with the above feedstocks.

Resource recovery potential from secondary components of segregated municipal solid wastes.

Fermentable components of municipal solid wastes (MSW) such as fruit and vegetable wastes (FVW), leaf litter, paddy straw, cane bagasse, cane trash and paper are generated in large quantities at various pockets of the city. These form potential feedstocks for decentralized biogas plants to be operated in the vicinity. We characterized the fermentation potential of six of the above MSW fractions for their suitability to be converted to biogas and anaerobic compost using the solid-state stratified bed (SSB) process in a laboratory study. FVW and leaf litter (paper mulberry leaves) decomposed almost completely while paddy straw, sugarcane trash, sugarcane bagasse and photocopying paper decomposed to a lower extent. In the SSB process between 50-60% of the biological methane potential (BMP) could be realized. Observations revealed that the SSB process needs to be adapted differently for each of the feedstocks to obtain a higher gas recovery. Bagasse produced the largest fraction of anaerobic compost (fermentation residue) and has the potential for reuse in many ways.

Micro-treatment options for components of organic fraction of MSW in residential areas.

There is a growing interest in management of MSW through micro-treatment of organic fraction of municipal solid wastes (OFMSW) in many cities of India. The OFMSW fraction is high (>80%) in many pockets within South Indian cities like Bangalore, Chikkamagalur, etc. and is largely represented by vegetable, fruit, packing and garden wastes. Among these, the last three have shown problems for easy decomposition. Fruit wastes are characterized by a large pectin supported fraction that decomposes quickly to organic acids (becomes pulpy) that eventually slow down anaerobic and aerobic decomposition processes. Paper fraction (newsprint and photocopying paper) as well as paddy straw (packing), bagasse (from cane juice stalls) and tree leaf litter (typical garden waste and street sweepings) are found in reasonably large proportions in MSW. These decompose slowly due to poor nutrients or physical state. We have examined the suitability of these substrates for micro-composting in plastic bins by tracking decomposition pattern and physical changes. It was found that fruit wastes decompose rapidly to produce organic acids and large leachate fraction such that it may need to be mixed with leachate absorbing materials (dry wastes) for good composting. Leaf litter, paddy straw and bagasse decompose to the tune of 90, 68 and 60% VS and are suitable for composting micro-treatment. Paper fractions even when augmented with 10% leaf compost failed to show appreciable decomposition in 50 days. All these feedstocks were found to have good biological methane potential (BMP) and showed promise for conversion to biogas under a mixed feed operation. Suitability of this approach was verified by operating a plug-flow type anaerobic digester where only leaf litter gathered nearby (as street sweepings) was used as feedstock. Here only a third of the BMP was realized at this scale (0.18 m(3 )biogas/kg VS 0.55 m(3)/kg in BMP). We conclude that anaerobic digestion in plug-flow like digesters appear a more suitable micro-treatment option (2-10 kg VS/day) because in addition to compost it also produces biogas for domestic use nearby.