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The moisture content of municipal solid waste (MSW) and local precipitation events lead to the leachate generation from MSW landfills. The high concentration of organic pollutants in landfill leachate makes it hazardous, requiring treatment before disposal into the environment. Landfill Leachate is most commonly treated by reverse osmosis (RO), which generates large volumes of wastewater termed as RO reject. This investigation aims to stabilize the RO reject through an inexpensive and effective bioremediation strategy. A bench-scale aerobic suspended growth reactor study was conducted using three commercial conversion agents, namely EM.1, Bokashi powder, and coir pith powder. Overall bench-scale efficacy of 63% was achieved in this study. The onsite studies were conducted in 7.5 kL artificial ponds with 46% efficacy amid atmospheric influences and constraints. In contrast, the control pond with no conversion agents showed an increase in pollution concentration over the 100 days of retention time. The findings revealed that the investigated technology had a marginally lower evaporation rate and performed relatively well compared to traditional solar evaporation ponds. Moreover, the technology can be easily scaled-up and readily applied for RO reject treatment in MSW landfills.

Faecal sludge (FS) or septage collected from an onsite containment system such as septic tanks, pit latrines, bio-digester etc., is handled in sewage treatment facilities with the help of a co-treatment unit or tackled individually at faecal sludge treatment plants (FSTPs). Treatment of faecal sludge in FSTPs is a generally cumbersome, energy-intensive, and expensive process. Enhancing the size of the solid particle, dewatering, and disinfection are essential unit operations that contribute to a significant portion of the operational expenditure. Therefore, the present study took up the task of investigating and yielding a natural alternative to each of the above-delineated unit operations. Crushed seed powders of Moringa, Guilandina bonduc, Nirmali, Tamarind, Soap nut, Nutmeg, Jackfruit, and Custard apple seed powder experimented as natural coagulants. At the same time, a double-stitched cow dung-lined jute tube was utilized as the media for solid-liquid separation. Finally, Neem and Custard Apple seed and leaf powder were considered herbal disinfectants for the separated liquid and solid fractions, respectively. The findings of the physicochemical and biological analysis of the above unit operations were compared with a conventional polymer-based Geotube driven treatment scheme. The natural alternatives registered some promising outcomes. However, the combined treatment efficacy of 78.94% for pollutant removal and disinfection could not exceed the value of 99.01% offered by the conventional method. Moreover, herbal alternatives are scarce, expensive, and slow reacting. Therefore, the authors recommend further research to overcome the persisting issues with herbal alternatives for their field-scale adaptation.

Microplastics are classified as emerging pollutants of the aquatic environment, necessitating a comprehensive understanding of their properties for successful management and treatment. Wastewater treatment plants (WWTPs) serve as point sources of microplastic pollution of the aquatic and terrestrial (eco)systems. The first part of this review explores the basic definitions of microplastics, sources, types, physical and chemical methods of identifying and characterizing microplastics in WWTPs. The next part of the review details the occurrence of microplastics in various unit processes of WWTPs and sewage sludge. Followed by this, various methods for removing microplastics from wastewater are presented. Finally, the research gaps in this area were identified, and suggestions for future perspectives were provided. HIGHLIGHTS Wastewater treatment plants act as point sources of microplastic pollution.; Microplastics in wastewater treatment plants are diverse in composition, size, shape and origin.; Microplastics are seen in all unit processes of wastewater treatment plants.; Wastewater treatment plants remove bulk of microplastics entering them.; Majority of microplastics enter the environment from sludge generated in wastewater treatment plants.

Conventionally, nanoparticles are synthesized by chemical and physical routes. However, the synthesis of nanoparticles through conventional approaches has many drawbacks, such as being expensive, use of hazardous substrates, generation of toxic by-products, and consumption of enormous energy. To overcome the demerits mentioned above, biological agents such as plants and microorganisms can synthesize nanoparticles. Commonly termed as the green synthesis of nanoparticles, this is an emerging field in recent times. The advantages of the green synthesis of nanoparticles include nontoxic by-products, cost effectiveness, diversity in size, shape, composition, and production sustainability per se. Nanoparticle synthesis mediated by plants is one of the standard approaches. Soluble organics, including secondary metabolites of plant extracts, can reduce metal salts to metal nanoparticles. These nanoparticles can be used as anticancer, antimicrobial, and antifungal agents as well as for other diverse applications. However, another green synthesis method is mediated through bacteria because they have innate mechanisms to reduce metal salts to metal nanoparticles. Sewage sludge obtained from sewage treatment plants is a rich source of various bacterial species used in nanoparticle biosynthesis. Green synthesis of silver nanoparticles with a particular focus on the processes mediated by plant and bacteria is discussed in this chapter.

It is evident from the literature that research on the treatment of leachate generated from municipal solid waste (MSW) landfills has been a focus area of environmental management. However, the available information is discrete because most studies have reported only one or a couple of aspects of either closed or active MSW landfill leachate treatment. Hence, this investigation has focused on comprehensive attributes of both closed landfill leachate (CLL) and active landfill leachate (ALL), including generation, characterisation, and toxicity assessment to quantify and establish their pollution potential. The results indicated that CLL generation is higher (188.59 m

There is a dire need to replace the chemical buffers that regulate the redox environment in single-stage anaerobic digestion (AD) of food waste (FW). Hence, the applicability of grass clippings (GC) as an eco-friendly buffering agent and biomass during the anaerobic co-digestion of FW was explored. A focus was primarily given on the effects of GC on the redox environment and acidogenesis. Concomitantly the production of volatile fatty acids, hydrogen and methane in mesophilic conditions was monitored. Organic load and substrate to inoculum ratio were kept constant in all the experiments, and no chemical buffer was used. The results revealed that GC regulated the redox environment by inhibiting rapid pH drop in the digester with 10 % GC. The addition of 2, 4, and 6 % GC promoted acidogenesis with increased production of acetic and butyric acids; whereas, 8 and 10 % GC promoted solventogenesis with ethyl alcohol production. Hydrogen generation from the experiments with GC was in the range of 27-30 % of the total biogas, which was marginally higher than from the control (25 %). Methane concentration was negligible in the biogas generated from all experiments. The acidification rate, VFA production/consumption rate, specific hydrogen yield, hydrogen conversion efficiency, and volatile solid removal were maximum and minimum in the reactors with 6 and 10 % GC, respectively. From the above results, it can be concluded that the addition of GC to FW would regulate the sudden pH changes and enhance the production of value-added biochemicals, to make the process cost-effective.

In present investigation, effect of diverting acidogenic off-gas from leached bed reactor (LBR) to up-flow anaerobic sludge blanket (UASB) reactor during semi-continuous food waste (FW) anaerobic digestion was evaluated. In test LBR headspace pressure (3.3 psi) was maintained with intermittent headspace gas transfer into UASB. In control, same headspace pressure was maintained without gas transfer. The semi-continuous FW addition affected the characteristics and production of leachate in control and test LBR. The cumulative COD, total soluble products and methane yields were 1.26, 1.37 and 3 times higher in the test LBR than the control. The acetate and methane yields from test LBR were 697.8 g.kgVSadded-1 and 167.55 mL.gCOD-1feeding. Acidogenic gas transfer maintained low partial pressure of hydrogen and the hydrogen to carbon-di-oxide ratio in the headspace of LBR, which were thermodynamically favorable for microbial metabolism and concomitant high-rate production of acetate-rich volatile fatty acid and methane-rich biogas from FW.

This work characterized microbial community composition and diversity of the ‘methanogenic phase’ of a two-staged anaerobic sequence batch reactor(ASBR). The ASBR was operated for biogas production from abattoir wastewater, heterogeneous fruits-vegetables solid waste, and their combinations. The Metagenomic DNA of digestate from the ASBRs was extracted and amplified with sample-specific primers targeting the (V3-V4) hypervariable regions of the 16S rRNA gene. The 16S rRNA Amplicons were sequenced using the Illumina MiSeq. The overall microbial composition was influenced by the nature of substrates. The sequence analysis revealed that the methanogenic stage ASBRs were dominated by bacterial and archaeal members most closely related to Proteobacteria, Firmicutes, Planctomycetes, and Euryarchaeota. Out of identified methanogens genera, Methanosaeta and Methanosarcina were the most dominant. Compared to Methanosarcina, the unclassified spp. of a member of the Methanosaeta genus was the most dominant. This implied the Methanosaeta spp. were mainly responsible for the biomethanation of the substrates.

Establishment of analytical methods for detection and characterization of nanoparticles in the environment are gaining prominence across the globe. The present study was designed to quantify titanium (Ti) and to characterize titanium dioxide nanoparticles (TNP) from a municipal sewage treatment plant, by inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of Ti & TNP were 1085 & 13.6 mg/kg in the influent sewage and 298 & 3.3 mg/kg in the aeration tank contents, respectively. The size of TNP ranged between 71-145 nm in the sludge fraction. Determining environmentally realistic concentrations of TNP could serve as a tracer material for characterization of those nanomaterials with similar size and aggregation properties. Furthermore, inference of Ti and TNP in municipal sewage in the study will also help in environmental risk assessment of nanomaterials.

Establishment of analytical methods for detection and characterization of nanoparticles in the environment are gaining prominence across the globe. The present study was designed to quantify titanium (Ti) and to characterize titanium dioxide nanoparticles (TNP) from a municipal sewage treatment plant, by inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of TiTNP were 108513.6 mg/kg in the influent sewage and 2983.3 mg/kg in the aeration tank contents, respectively. The size of TNP ranged between 71-145 nm in the sludge fraction. Determining environmentally realistic concentrations of TNP could serve as a tracer material for characterization of those nanomaterials with similar size and aggregation properties. Furthermore, inference of Ti and TNP in municipal sewage in the study will also help in environmental risk assessment of nanomaterials.