Search Results (35)

Nature-based systems predominantly treat faecal sludge in developing regions due to their cost-effectiveness and operational simplicity. These systems, including solid–liquid separation, anaerobic digestion, dewatering, phytofiltration, and composting produce, treated sludge with variable characteristics. However, application-specific characterisation of treated sludge from these systems remains limited, hindering evidence-based agricultural application. This study investigated thirty treated faecal sludge samples from unplanted drying beds, planted drying beds, and co-composting, with a focus on their soil application potential. Nonparametric statistical analysis revealed that treatment processes significantly influenced the key properties, including electrical conductivity, total organic carbon, total nitrogen, and potassium content. The co-compost yielded comparatively higher conductivity (4.9 dS/m) and potassium levels (1.09%) but lower total nitrogen (2.15%) and organic carbon contents (28%). Additionally, co-composted sludge exhibited a balanced nutrient profile with a wide range of micronutrients and high variability. Despite this variability, all samples met the Indian compost quality guidelines for heavy metals. The findings underscore the importance of treatment-specific characterisation to inform appropriate soil application rates and ensure safe use. This study contributes to the development of quality criteria and guidelines for use of faecal sludge in agriculture, particularly in regions such as India, where no regulatory framework currently exists for faecal sludge application. Full article

The mechanical properties of faecal sludge (FS) influence its moisture retention characteristics to a greater extent than other properties. A comprehensive fundamental characterisation of the mechanical properties is scarcely discussed in the literature. This research focused on bulk and true densities, porosity, particle size distribution and zeta-potential, extracellular polymeric substances, rheology and dilatancy, microstructure analysis, and compactibility in the context of using the FS as a substitute for soil in land reclamation and bioremediation processes. FSs from different on-site sanitation systems were collected from around Durban, South Africa. The porosity of the FSs varied between 42% and 63%, with the zeta-potential being negative, below 10 mV. Over 95% of the particles were <1000 µm. With its presence in the inner part of the solid particles, tightly bound extra-cellular polymeric substances (TB-EPSs) influenced the stability of the sludge by tightly attaching to the cell walls, with the highest being in the septic tank with the greywater sample. More proteins than carbohydrates also confirmed characterised the anaerobic nature of the sludge. The results of the textural properties using a penetrometer showed that the initial slope of the positive part of the penetration curve was related to the stiffness of the sludge sample and similar to that of sewage sludge. The dynamic oscillatory measurements exhibited a firm gel-like behaviour with a linear viscoelastic behaviour of the sludges due to the change in EPSs because of anaerobicity. The high-TS samples exhibited the role of moisture as a lubricating agent on the motion of solid particles, leading to dilatancy with reduced moisture, where the yield stress was no longer associated with the viscous forces but with the frictional contacts of solid–solid particle interactions. The filtration–compression cell test showed good compactibility, but the presence of unbound moisture even at a high pressure of 300 kPa meant that not all unbound moisture was easily removable. The moisture retention behaviour of FS was influenced by its mechanical properties, and any interventional changes to these properties can result in the release of the bound moisture of FS. Full article

This study optimized the organic matter solubilization of faecal sludge (FS). FS was treated in a microwave oven at varying microwave power and treatment times. Changes in total solids (TS), volatile solids (VS), total chemical oxygen demand (TCOD), and soluble chemical oxygen demand (sCOD) were measured. A response surface methodology (RSM) optimized organic matter solubilization during microwave treatment. A central composite design was employed, and the observed responses were used to fit a second-order response surface model. Microwave treatment at 14,000 kJ/kg. TS reduced FS volume by 58%. The VS/TS ratios remained similar before and after microwave treatment. The solubilization of organic matter (measured by the sCOD/TCOD ratio) increased after microwave treatment, showing an initial linear increase with specific energy followed by a decrease. The highest solubilization was 38%, achieved at a microwave power level of 630 W for 3 min. Organic matter solubilization was more sensitive to contact time than microwave power. RSM determined the optimized conditions to be 617.7 W and 2.4 min, within the experimental design boundaries. These findings align with similar observations from other studies using wastewater sludge. The results suggest that microwave treatment can achieve multiple FS treatment objectives. Optimal operating conditions should be identified if the aim is to solubilize organic matter in FS. Full article

This study aimed to treat sewage sludge through microwave irradiation at a laboratory scale. The objective was to investigate the effect of microwave irradiation on microorganisms, water content, organic matter, and agronomic nutrients present in sewage sludge. Three types of sewage sludges obtained from a full-scale wastewater treatment plant were considered: Sludge A (raw sludge), Sludge B (subjected to 15 days of solar exposure, achieving 48% dryness), and Sludge C (exposed to solar conditions and left open to the air for 23 months, reaching 94% dryness). These diverse sludges were exposed to microwave irradiation at various power levels (analysed variables: ε (Watts/g), θ (°C), T (min)). The specific exposure powers and temperature levels for the water reduction analysis were: 555, 955, 1355, and 1500 Watts/g and 55, 75, 95, and 105 °C, respectively. On the other hand, microbiological and agronomic nutrient analyses were conducted at 75 °C–1355 W and 95 °C–1355 W. After microwave exposure experiments, the results demonstrated the high effectiveness of microwave technology in eradicating indicator microorganisms of faecal contamination and reducing sludge volume while not affecting trace elements of significant agricultural value. The reduction in Escherichia Coli revealed that 4 min of irradiation was necessary to completely eliminate it to 0 ulog, indicating a 100% reduction, in Sludge A. In Sludges B and C, an additional 1 min was needed under conditions of 75 °C and 1355 W for a mass of 50 g. Moreover, Sludge A (46.27 × 10⁵ or 4.80 ulog of dry matter), Sludge B (1.29 × 10⁶ or 6.11 ulog of dry matter), and Sludge C (8.77 × 10⁴ or 4.94 ulog of dry matter) were heavily contaminated with faecal coliforms. It took 6 min to reduce faecal coliforms to below the detection threshold. Full article

The use of faecal sludge (FS) in anaerobic digestion (AD) requires a perfect knowledge of their composition. Considered as a very heterogeneous material, the high variability of FS can disturb biodigesters’ functionality and impact biogas production. Unique in West Africa, Kossodo’s biogas plant in Ouagadougou receives sludge from septic tanks and pit latrines. To evaluate the quality of sludge discharged in this treatment plant and its ability for AD, a characterization of 130 FS trucks from several onsite sanitation facilities was carried out. Physico-chemicals, including heavy metals and microbiological parameters, were analyzed using standard protocols. A biochemical methane potential test was employed to evaluate biogas yield. Results showed that raw sludge averaged 1.12% total solids (TS), 54.74% volatile solids (VS), 9253 mg/L chemical oxygen demand (COD), and 1645 mg/L biochemical oxygen demand (BOD). Settled faecal sludge exhibited higher levels of total coliforms, E. coli, helminth eggs, and heavy metals. Heavy metal levels met AD standards defined by VDI 4630, with decreasing toxicity order: Zn > Mn > Cu > Cr > Ni > Pb > As ≥ Hg. The carbon-to-nitrogen (C/N) ratio was 6.7 ± 4.3, indicating unsuitability for AD. Sludge settling increased C/N ratio by 46%, which was still below optimal AD conditions (20–30). Methane yield of raw and settled FS averaged 61 ± 0.2 and 156 ± 3.2 NL CH₄/kg VS removed, respectively. Co-substrate addition could enhance the methanogenic yield of these sludges. This study provides a valuable database on the characteristics of FS, supporting sustainable recovery options. Full article

The disposal of human faecal sludge (FS) is one of the biggest environmental problems. It can be solved by using FS as an agricultural fertilizer. However, this is hampered by the presence of pathogenic microflora and high organic matter content in FS. This paper proposes a novel treatment approach for FS to address these issues. It consists of the preliminary aerobic incubation of FS with the bioaugmentation of bacterial culture Alcaligenes faecalis DOS7. A. faecalis has been shown to inhibit the growth of various microorganisms, including coliforms (Escherichia coli). For the treatment of FS, three tanks with a volume of 1 m³ each, equipped with a mixing and aeration system, were used. A. faecalis culture was introduced into two experimental tanks at a concentration of 10⁶ and 6.5 × 10⁶ cells/mL. The 11-day incubation in the experimental tanks resulted in the decomposition of organic matter in the FS that was several times faster than in the control (p < 0.05). Total suspended solids decreased 2.5–5-fold, chemical oxygen demand decreased 1.8-fold, 5-day biochemical oxygen demand decreased 1.5–2-fold. At the same time, after 4 days of incubation, no coliforms were detected in the experimental tanks, and in the control, coliforms accounted for 13.9% of the total number of cells after 11 days of incubation. The proposed method of FS pretreatment is a real alternative to the existing ones and can be used both individually and in combination with other methods, for example, composting. Full article

Stabilised organic solids derived from sewage sludge (“biosolids”) are applied to land as an alternative to disposal as landfill. This study evaluated the long-term effects of biosolids applied to forestry plantations on the adjacent intertidal habitats of Rabbit Island (New Zealand). On this island, biosolids are applied to enhance the growth of trees (Pinus radiata). Shoreline topography, macroalgal cover, sediment grain size, the concentrations of nutrients, trace metals, and faecal indicator bacteria, and benthic infaunal communities were studied in 2008, 2014, and 2019 at twelve intertidal transect sites (four “reference” and eight “application”) adjacent to forestry blocks where biosolids have been applied over a period of 24 years. The sediment composition did not differ significantly between the survey years or between the reference and application sites. Total nitrogen concentrations in the sediments increased over time at some transects, but such increases were not consistent among the application transects. No symptoms of excessive algal growth, sediment anoxia, and hydrogen sulphide odours were observed at most sites. Key infaunal taxa were similar between the reference and application transects. Overall, no long-term adverse changes to intertidal habitats attributed to biosolids application were detected between the reference and application sites. This study shows that biosolids application can co-occur without detectable adverse effects on nearby intertidal environments. In a global context of rising concern over climate change, environmental pollution, and resource scarcity, forest fertilisation with biosolids can facilitate biomass production and soil development while protecting valued coastal ecosystems. Full article

Full-scale pyrolysis of faecal sludge in developing nations is an emerging technology for the complete removal of pathogens and the concurrent creation of biochar, a soil amendment shown to enhance crop productivity. Currently there is little information on the effects of faecal sludge biochar on soil and crop yield. Faecal sludge biochar was applied to an acidic, sandy soil to assess its effects on plant growth and yield in Micro-Tom, a model cultivar of tomato (Solanum lycopersicum L.). We examined four soil application treatments: a control soil, fertilizer treatment, biochar treatment, and a combined biochar and fertilizer treatment. The combined treatment of biochar and fertilizer together produced a tomato yield 2980% greater than the tomato yield from control soil, whereas biochar on its own increased the yield by 1060%. There was no significant difference in plant height between the combined biochar and fertilizer application and biochar on its own; however, both treatments significantly increased plant height compared to control soil. Below ground biomass showed a similar pattern, with no significant difference between biochar alone and combined biochar and fertilizer treatments, and both treatments resulted in significantly increased below ground biomass compared to control soil. The combined biochar and fertilizer treatment resulted in significantly lower water runoff than all other treatments. These findings have great potential implications for increasing food security and the creation of more sustainable agricultural practices, especially in developing regions. Full article

Full-scale pyrolysis of faecal sludge is a credible technology for the safe removal of pathogens and the concurrent creation of biochar, which has been shown to enhance crop productivity. Faecal sludge biochar has the potential to improve acidic, low nutrient soils and crop yield in developing nations more at risk of climate change and food insecurity. Little research has been conducted into public acceptance of faecal sludge biochar as a soil enhancer in agriculture. In this study of the public in Swansea, Wales, an online survey examines their awareness of, and comfort levels of eating food grown using biosolids, wood biochar and faecal sludge biochar. Our findings show that males were almost twice as likely than females to have a positive perception of biosolids (OR 1.91, p value 0.004) and faecal sludge biochar (OR 2.02, p value 0.03). Those in the oldest age group (65+) were almost five times more likely to have a positive view of faecal sludge biochar than the youngest age group (OR 4.88, p value 0.001). Deployment of faecal sludge biochar must overcome a “disgust effect” related to its human faecal origins. This factor must be centrally taken into account when implementing management and policy decisions regarding the land application of biosolids and faecal sludge biochar. Full article

Sanitation workers provide an essential public service that is key to achieving the Sustainable Development Goals (SDG), but often costs them their dignity and health. Many governments in low- and middle-income countries fail to support their sanitation workforce. This is due, in part, to a lack of knowledge about sanitation workers’ needs and the challenges they face. This study aims to address this knowledge gap through four assessments conducted in Burkina Faso, Nigeria, Tanzania, and Zambia that explored the health and safety, financial security, legal protection, and dignity of sanitation workers. Methodologies included literature reviews, key informant interviews (110), focus group discussions (7), and a survey. The findings suggest that sanitation workers across Africa face serious health and safety risks, heightened by a lack of adequate protective equipment and access to healthcare services. Their pay is insufficient and unstable, and the regulatory environment offers them little legal protection. Many also face stigma and discrimination. These challenges were found to be more acute for manual emptiers and those working informally. The study concludes that governments must develop context-specific action plans to support their sanitation workforce, guided by the results of national and sub-national assessments and in collaboration with sanitation worker groups. Full article

When soils are phosphorus (P) deficient, external sources in the form of fertilisers have to be applied to increase crop yields. The world depends on mined sources for P fertilisers, and recent reports indicate that an increase in the human population has led to rising demand for P fertilisers, making its future supply uncertain. A low supply of chemical P fertilisers may lead to food insecurity. Although the efficacy of organic sources of P is unclear, organic waste materials containing P can potentially replace inorganic P sources. Previously, organic fertilisers have been used to supply N and even P, but the application rates were mostly N based, resulting in inconsistent and comparable results. This research was conducted to understand P mineralisation and the availability of the P-based organic fertilisers. The results showed that available P in the soil at 3 weeks accounted for 50%, 6 weeks accounted for 49%, and 9 weeks counted for 46% of the maize yield. The organic P sources maintained soil available P above the threshold available P value in Malawi. The P sources did not affect the maize P use efficiency (PUE). The results indicate that organic P sources could be used as an alternative fertiliser for maize production in Malawi. Full article

This study investigated the effect of locally available bulking agents on the faecal sludge (FS) composting process and quality of the final FS compost. Dewatered FS was mixed with sawdust, coffee husk and brewery waste, and composted on a pilot scale. The evolution of physical and chemical characteristics of the composting materials was monitored weekly. Results indicate that bulking agents have a statistically significant effect (p < 0.0001) on the evolution of composting temperatures, pH, electrical conductivity, nitrogen forms, organic matter mineralisation, total organic carbon, maturity indices, quality of the final compost and composting periods during FS composting. Our results suggest reliable maturity indices for mature and stable FS compost. From the resource recovery perspective, this study suggests sawdust as a suitable bulking agent for co-composting with FS—as it significantly reduced the organic matter losses and nitrogen losses (to 2.2%), and improved the plant growth index, thus improving the agronomic values of the final compost as a soil conditioner. FS co-composting can be considered a sustainable and decentralised treatment option for FS and other organic wastes in the rural and peri-urban communities, especially, where there is a strong practice of reusing organic waste in agriculture. Full article

Developing countries are confronted with general issues of municipal wastewater management and treatment. Untreated wastewater and faecal sludge from septic tanks and traditional toilets are often discharged into rivers and used for urban agriculture without any treatment to minimize potential biorisks. Such practices result in potential environmental and public health risks. In this study, a wastewater treatment plant prototype coupled with Moringa oleifera seeds treatment was developed to evaluate their effectiveness for the reduction of faecal indicator bacteria and antibiotic-resistant bacteria in domestic wastewater. We demonstrated that that the proposed wastewater treatment plant prototype reduces bacteria by 99.34%. A high removal of the bacteria load was obtained after the addition of Moringa oleifera seeds into waters, with removal rates of 36.6–78.8% for E. coli, 28.3–84.6% for faecal coliform, 35.3–95.6% for Vibrio cholera and 32.1–92.4% for total flora. A similar effect of Moringa oleifera seeds was noted for the removal of antibiotic-resistant bacteria, extended-spectrum beta-lactamases and carbapenem-resistant Enterobacteriaceae, with a removal rate of up to 98% for E. coli and faecal coliform, 100% for Vibrio cholera and 91.96% for total flora. This study demonstrated the high removal efficiency pathogens and antibiotic-resistant bacteria from domestic wastewater using Moringa oleifera seeds. Full article

Local government partnerships for producing services are ubiquitous in many countries. However, the approach has rarely been applied in India—likely owing to a history of centralized planning and independent urban and rural governance systems. Nonetheless, the country’s transforming sanitation landscape could benefit from intergovernmental partnerships for scaling services with speed and efficiency. The ongoing national sanitation program has espoused the approach in theory but the body of practice to support its wide deployment is sparse. This paper critically reviews one of the first experiments with the approach for producing sanitation services in the Dhenkanal district, Odisha, India. We ask the question: what can Dhenkanal’s case tell us about the challenges and opportunities for delivering sanitation services through local-level intergovernmental urban–rural partnerships in India? As part of our practice research, we supported the district government pilot the approach. The data, consultations, and observations underpinning the experiment form the basis of our insights. We find that the urban–rural partnership increased access to sanitation services among rural households within a short period, lowered service charges, and clarified institutional responsibilities. The experiment highlighted issues relating to planning, responsibility, accountability, and financing that need tackling in order to strengthen the model going forward. We recommend that evolving a definitive model(s) of intergovernmental partnerships would require experimenting with the approach in diverse institutional contexts and granting governments the flexibility to recreate and renegotiate the form of the partnership. Full article

The current paper provides a review and meta-analysis of the practical implications of disaster risk management related to the ventilated improved latrines in South Africa. This technology is evaluated through its legacy and novel challenges of disaster risk reduction. In the current article, the methodology adopted was a literature review and meta-analyses. The results indicate that the in-situ treatment and breakdown of faecal sludge in the ventilated improved pit latrines is not always taking place and that anaerobic digestion might not always be feasible. New strategies are proposed to manage the sanitation-related risks in South Africa by specifying more exact dimensions for the newly built ventilated improved pit latrines by suggesting the use of novel sanitation additives such as fly ash to enhance on-site and in situ treatment, as well as ex situ treatment of the pit latrine faecal sludge. Regular maintenance can lead to prevention of the dysfunctional character of the ventilated improved pit latrines as a functional sanitation technology and a user-friendly hygiene barrier to the spread of sanitation/WASH-related epidemics or infectious diseases. The implementation of the novel strategies should be enhanced by the application of the (Environmental) Technology Assessment in sanitation service delivery in South Africa. Full article