Effective management of fecal sludge (FS) is essential for preventing environmental and public health risks. Developing safe and efficient FS treatment technology is crucial for reducing the health risks of onsite sanitation systems. In this study, bioelectrochemical toilets (BETs) were developed to treat FS onsite. Compared with the open-circuit BETs (OC-BETs), BETs exhibited higher removal efficiencies for total organic carbon, total nitrogen, and total phosphorus. Specifically, the enhancements in removal efficiencies were 18.82 ± 1.73 %, 7.28 ± 0.32 %, and 11.41 ± 0.05 % for urine, and 19.28 ± 4.08 %, 21.65 ± 1.23 %, and 24.68 ± 0.95 % for feces, respectively. Microbiome analysis indicated that the dominant populations were affiliated with electroactive bacteria (Desulfuromonas and Pseudomonas) in the electrode biofilm of BETs. The species co-occurrence network showed that the electrode biofilm microbiome in BETs had more complex correlations than that in OC-BETs, suggesting that a weak electrical current enhanced the microbiome stability. The relative abundance of antibiotic resistance genes in BETs and OC-BETs reduced by 59.85 ± 1.32 % and 53.01 ± 2.81 % compared with the initial FS, respectively. These findings indicate that BETs are an alternative system for enhancing onsite treatment of fecal sludge and provide a theoretical foundation for the implementation of BETs.

A rise in population and urbanization demanded that a robust fecal sludge management (FSM) value chain be used to restructure the sanitation system throughout the world securely. A significant global need exists to adopt efficient and sustainable FSM. On-site sanitation systems (OSS) produce fecal sludge (FS). FS is produced when excreta and blackwater are combined and stored or treated, either alone or in combination with greywater. FS can be semisolid or slurry and raw or partially digested. Critical examination of FS characteristics, i.e., biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS), and pathogen count, varies from 600-56,836 mg/l, 6656 to 201,200 mg/l, 830-123,000 mg/l, and 105 to 109 E. coli/l of FS respectively. Helminth eggs range from 2500-25,000/l of FS. Public health and the environment are negatively impacted by septic tank overflows and the careless discharge of FS into open spaces affecting groundwater quality, water bodies, irrigation fields, open drains, places outside villages, etc. Thus, deciding on a proper treatment technology for FS before discharging it into open land or reusing FS is essential to create a pollution-free environment. This paper highlights the practices adopted for FSM under its different processes, such as collecting, characterization, treating, and reusing of on-site FS and bibliometric analysis on documents on fecal sludge. A thorough analysis has been carried out by reviewing all important literature available globally.

Progress toward Sustainable Development Goals for global access to safe sanitation is lagging significantly. In this Feature, we propose that misleading terminology leads to errors of categorization and hinders progress toward sanitation service provision in urban areas. Binary classifications such as \"offsite/onsite\" and \"sewered/nonsewered\" do not capture the need for \"transport to treatment\" or the complexity of urban sanitation and should be discarded. \"Fecal sludge management\" is used only in the development context of low- or middle-income countries, implying separate solutions for \"poor\" or \"southern\" contexts, which is unhelpful. Terminology alone does not solve problems, but rather than using outdated or \"special\" terminology, we argue that a robust terminology that is globally relevant across low-, middle-, and upper-income contexts is required to overcome increasingly unhelpful assumptions and stereotypes. The use of accurate, technically robust vocabulary and definitions can improve decisions about management and selection of treatment, promote a circular economy, provide a basis for evidence-based science and technology research, and lead to critical shifts and transformations to set policy goals around truly safely managed sanitation. In this Feature, the three current modes of sanitation are defined, examples of misconceptions based on existing terminology are presented, and a new terminology for collection and conveyance is proposed: (I) fully road transported, (II) source-separated mixed transport, (III) mixed transport, and (IV) fully pipe transported.

The safe management of fecal sludge from the 3.4 billion people worldwide that use onsite sanitation systems can greatly reduce the global infectious disease burden. However, there is limited knowledge about the role of design, operational, and environmental factors on pathogen survival in pit latrines, urine diverting desiccation toilets, and other types of onsite toilets. We conducted a systematic literature review and meta-analysis to characterize pathogen reduction rates in fecal sludge, feces, and human excreta with respect to pH, temperature, moisture content, and the use of additives for desiccation, alkalinization, or disinfection. A meta-analysis of 1,382 data points extracted from 243 experiments described in 26 articles revealed significant differences between the decay rates and T99 values of pathogens and indicators from different microbial groups. The overall median T99 values were 4.8 days, 29 days, >341 days, and 429 days for bacteria, viruses, protozoan (oo)cysts, and Ascaris eggs, respectively. As expected, higher pH values, higher temperatures, and the application of lime all significantly predicted greater pathogen reduction rates but the use of lime by itself was more effective for bacteria and viruses than for Ascaris eggs, unless urea was also added. In multiple lab-scale experiments, the application of urea with enough lime or ash to reach a pH of 10 - 12 and a sustained concentration of 2,000 - 6,000 mg/L of non-protonated NH3-N reduced Ascaris eggs more rapidly than without urea. In general, the storage of fecal sludge for 6 months adequately controls hazards from viruses and bacteria, but much longer storage times or alkaline treatment with urea and low moisture or heat is needed to control hazards from protozoa and helminths. More research is needed to demonstrate the efficacy of lime, ash, and urea in the field. More studies of protozoan pathogens are also needed, as very few qualifying experiments were found for this group.

This study investigated the efficiency of fecal sludge conditioning using peroxydisulfate (PDS) activated by zero-valent iron (ZVI). For fecal sludge obtained from public toilets in a densely-populated rural area in China, the ZVI/PDS coupling greatly improved its dewaterability as well as the supernatant quality in terms of organic matter and nutrient contents. The capillary suction time (CST) and supernatant turbidity of fecal sludge can be reduced up to 97% and 73% respectively in 10 min by the combination of 0.15 g/g TS ZVI and 0.2 g/g TS PDS. Protein removal, especially for tightly and loosely bound extracellular-polymeric-substance (EPS), is more linearly correlated to CST reduction than polysaccharide removal. Fecal sludge dewatering was improved by the hybrid functions of radical oxidation and iron coagulation. The ZVI/PDS treatment produced larger and looser flocs, probably because 1) surface ionic and hydrophilic groups of fecal sludge were reduced, 2) surface charge was neutralized, and 3) secondary structures of EPS proteins were altered by the radicals. The excellent fecal sludge dewatering was related to strengthened particle hydrophobicity and reduced sludge viscosity and compressibility. The results highlight that the ZVI/PDS combination is potentially an effective conditioning approach for fecal sludge from public toilets.

The decomposition and pathogen inactivation of fecal sludge (FS) are vitally important for safely managing onsite sanitation and protecting public and environmental health. However, the microbiome and virome assemblages in FS after chemical and biological treatments remain unclear. Here, we reported the differences in the solid reduction and microbiomes of FS subjected to potassium ferrate (PF), alkali (ALK), and sodium hypochlorite (NaClO) pretreatments and anaerobic digestion (AD). The PF and NaClO pretreatments enhanced FS hydrolysis and pathogen suppression, respectively; AD suppressed Gram-positive bacteria. Most of the viromes were those of bacteriophages, which were also shaped by chemical pretreatments and AD. Metatranscriptome analysis revealed distinct gene expression patterns between the PF- and ALK-pretreated FS and the subsequent AD. Differentially expressed gene profiles indicated that genes related to biological processes, molecular functions, and transcriptional regulators were upregulated in ALK-AD and PF-AD samples. These findings suggested that the effect of different treatment technologies on the viral diversity, pathogen abundance, and metabolic function of the core microbiome extends beyond FS decomposition and that the use of combined processes would provide possible alternatives for FS management in pandemic emergencies.

Didecyldimethylammonium chloride (DDAC) and polyhexamethylene guanidine (PHMG) exhibit high antimicrobial activity and are widely used as biocidal agents in chemical toilet additives for the management of fecal sludge (FS). Disposal of such biocide-treated FS to a wastewater treatment plant (WWTP) is a major environmental problem. It is possible to reduce environmental damage through the use of biocidal agents, which easily decompose after performing their main biocidal functions. In this work, it is proposed to use the fact of a gradual increase in pH of FS from the initial 7.5 to 9.0-10.0 due to the decomposition of urea. Six biocidal compounds were selected that are capable of rapidly degrading in an alkaline environment and one that naturally degrades upon prolonged incubation. Four of them: bronopol (30 mg/L), DBNPA (500 mg/L), Sharomix (500 mg/L), and sodium percarbonate (6000 mg/L) have shown promise for environmentally friendly management of FS. In selected dosage, they successfully reduced microbial activity under both aerobic and anaerobic conditions and are cost-effective. After 10 days of incubation, degradation of the biocide occurred as measured by biological oxygen demand (BOD5) in biocide-treated FS. Such FS can be discharged to WWTP without severe damage to the activated sludge process, the need for dilution and additional procedures to neutralize toxicity.

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Fecal sludge and septage (FSS) are more concentrated than domestic wastewater which makes it difficult to treat and requires immediate attention otherwise, it leads towards serious environmental problems. In this review, an attempt has been made to highlight and discuss the various aspects of fecal sludge and septage management (FSSM) like its generation, characterization, containment, transportation, treatment, reuse and disposal. A comparison of existing fecal sludge treatment plants and technologies has been reviewed considering land requirement, capital cost, operation and maintenance cost, advantages and disadvantages. Based on the existing practices and review, a techno-economic treatment scheme is designed and proposed for solid-liquid separation and treatment of FSS with resource-recovery as fertilizer, material for construction, energy and treated effluent. To make FSSM, self-sustainable, a revenue generation model is also delineated for the researchers and decision-makers to evaluate its feasibility and implementation, especially in developing and underdeveloped countries.

Toxic shock caused by the discharge of biocide-contaminated fecal sludge (FS) from chemical toilets to conventional wastewater treatment plants (WWTP) can be a major problem in activated sludge operation. It is necessary to develop new environmental approaches to mitigate the toxicity of biocides in order to avoid degrading the performance of WWTP. \"Latrina\", a chemical toilet additive containing didecyldimethylammonium chloride and polyhexamethylene guanidine, is widely used in environmentally safe toilet complexes (ESTC) on Russian railway trains to deodorize FS and control microbial activity. In this work, seven biocide-resistant bacterial strains were isolated and identified from the FS of ESTC. The values of the minimum inhibitory and bactericidal concentrations of biocides for the isolated strains were 4.5-10 times higher than for the collection microorganisms. The bacterium Alcaligenes faecalis DOS7 was found to be particularly resistant to \"Latrina\", the minimum inhibitory concentration of which was almost 30 times higher than recommended for ESTC. Biological products based on isolated bacterial strains proved to be effective for FS biodegradation under both aerobic and anaerobic conditions. The results of the biochemical oxygen demand test and the newly developed disk-diffusion bioassay confirmed that isolated strains contribute to reducing toxicity of biocidal agents in FS. Hyper-resistance, non-pathogenicity, and potential plant growth-promoting ability make A. faecalis DOS7 promising for use in various biological products for wastewater treatment and bioremediation of soils contaminated with biocides, as well as in agriculture to increase plant productivity.