Search Results (7)

This study investigated a phototrophic approach to close nutrient loops by using landfill leachate as a culture medium to produce biomass and polyhydroxybutyrate (PHB) from a thermotolerant strain of Potamosiphon sp. A multi-cycle reuse scheme in which post-culture leachate was partially replenished with fresh leachate and reused in successive cultivation rounds to increase the biomass concentration (g/L) and the intracellular PHB content (% w/w) was tested. Three operational variables were optimized (leachate replenishment percentage, number of reuse cycles, and sanitation method (autoclaving, UV irradiation, or no treatment)) via the Box–Behnken response surface method. Both response variables were modeled with high predictive accuracy (R² = 0.98 for biomass and R² = 1.00 for PHB content). According to the experimental data, leachate replenishment emerged as the key factor influencing nutrient availability—particularly nitrogen and phosphorus—and thus PHB accumulation. The optimized conditions (2.17% v/v fresh leachate, three reuse cycles, and UV sanitation) yielded predicted values of 0.29 g/L biomass and 3.48% w/w PHB. These results demonstrate the feasibility of a controlled multicycle reuse process that integrates effluent treatment and biopolymer synthesis, offering a low-input, circular biotechnological approach for sustainable leachate valorization. Full article

The present study investigates the potential of using fecal ash as an adsorbent and demonstrates a self-sustaining, optimized approach for urea recovery from wastewater streams. Fecal ash was prepared by heating synthetic feces to 500 °C and then processing it as an adsorbent for urea adsorption from synthetic urine. Since this adsorption approach based on fecal ash is a promising alternative for wastewater treatment, it increases the process’ self- sustainability. Adsorption experiments with varying fecal ash loadings, initial urine concentrations, and adsorption temperatures were conducted, and the acquired data were applied to determine the adsorption kinetics. These three process parameters and their interactions served as the input vectors for the artificial neural network model, with the percentage urea adsorption onto fecal ash serving as the output. The Levenberg–Marquardt (TRAINLM) and Bayesian regularization (TRAINBR) techniques with mean square error (MSE) were trained and tested for predicting percentage adsorption. TRAINBR was demonstrated in our study to be an ideal match for improving urea adsorption, with an accuracy of R = 0.9982 and a convergence time of seven seconds. The ideal conditions for maximum urea adsorption were determined to be a high starting concentration of 13.5 g.L⁻¹; a low temperature of 30 °C, and a loading of 1.0 g of adsorbent. For urea, the improved settings resulted in maximum adsorption of 92.8%. Full article

The twin challenges of lack of access to improved sanitation and food insecurity remain critical, particularly in the global south. With cognizance of the nutrient potential of human excreta, there has been increasing interest in linking sanitation innovations with agriculture by using nutrients recovered from human excreta for crop production, thus, closing the nutrient loop. While studies and field trials have explored and validated the technical feasibility of reusing nutrients recovered from human excreta in agriculture, there is still limited knowledge of its social acceptability. This study examined whether indigenous knowledge can be leveraged to increase the acceptability of human-excreta-derived plant nutrient sources such as treated effluent in agriculture. A qualitative research design comprising seven focus group interviews (five in rural areas and two in peri-urban areas) was conducted in KwaZulu Natal, South Africa. Findings from the focus groups reveal a willingness to grow and consume food using treated effluent. Additionally, participants made references to indigenous practices that encourage recycling and reuse of human excreta. Given the potential to simultaneously address issues of food insecurity and sanitation that characterize many peri-urban and rural areas in South Africa, we recommend further studies in this area. Full article

Challenges associated with rapid population growth, urbanization, and nutrient mining have seen increased global research and development towards ‘waste to wealth’ initiatives, circular economy models, and cradle-to-cradle waste management principles. Closing the nutrient loop through safe recovery and valorization of human excreta for agricultural use may provide a sustainable method of waste management and sanitation. Understanding the market demand is essential for developing viable waste management and sanitation provision business models. The pathways and processes for the safe recovery of nutrients from human excreta are well-documented. However, only anecdotal evidence is available on the willingness to pay for human excreta-derived material in agriculture. This review closes this gap by identifying and synthesizing published evidence on farmers’ willingness to pay for human excreta-derived material for agricultural use. The Scopus and Web of Science search engines were used to search for the literature. The search results were screened, and the data were extracted, charted, and synthesized using the DistillerSR web-based application. The findings show that understanding willingness to pay for human excreta-derived material is still a nascent and emerging research area. Gender, education, and experience are common factors that influence the farmers’ willingness to pay. The findings show that pelletization, fortification, labeling, packaging, and certification are essential attributes in product development. The wide-scale commercialization can be achieved through incorporation of context-specific socioeconomic, religious and cultural influences on the estimation of willingness to pay. Promoting flexible legislation procedures, harmonization of regional legislations, and creating incentives for sustainable waste recovery and reuse may also promote the commercialization of circular nutrient economy initiatives. More empirical studies are required to validate willingness to pay estimates, especially using the best practice for conducting choice experiments. Full article

This work is inspired by motion control of cleaning robots, operating in certain endogenous environments, and performing various tasks like door cleaning, wall sanitizing, etc. The base platform’s motion for these robots is generally similar to the motion of four-wheel cars. Most of the cleaning and maintenance tasks require detection, path planning, and control. The motion controller’s job is to ensure the robot follows the desired path or a set of points, pre-decided by the path planner. This control loop generally requires some feedback from the on-board sensors, and odometry modules, to compute the necessary velocity inputs for the wheels. As the sensors and odometry modules are prone to environmental noise, dead-reckoning errors, and calibration errors, the control input may not provide satisfactory performance in a closed-loop. This paper develops a robust-observer based sliding mode controller to fulfill the motion control task in the presence of incomplete state measurements and sensor inaccuracies. A robust intrinsic observer design is proposed to estimate the input matrix, which is used for dynamic feedback linearization. The resulting uncertain dynamics are then stabilized through a sliding mode controller. The proposed robust-observer based sliding mode technique assures asymptotic trajectory tracking in the presence of measurement uncertainties. Lyapunov based stability analysis is used to guarantee the convergence of the closed-loop system, and the proposed strategy is successfully validated through numerical simulations. Full article

The use of closed-loop sanitation systems (CLSS), or reuse-oriented sanitation systems, has increased in recent years, and such systems have been successfully implemented in many parts of the world. However, no research has explored Traditional CLSS (T-CLSS) for a long-term humanitarian situation. This study explores the strengths, weaknesses, opportunities and threats (SWOT) of T-CLSS in peri-urban and rural contexts in three different provinces in Afghanistan (the first study of its kind in Afghanistan). Participatory research tools, such as transect walks, focus group discussions, smart community gatherings and interactive workshops, were applied to assess the SWOT associated with T-CLSS. The results indicate that T-CLSS has been practiced historically in both peri-urban and rural areas using local and traditional knowledge, skills and technologies. The socio-cultural acceptance of the system in both rural and peri-urban areas is an important strength of this established system. However, due to chronic development challenges in the study regions, T-CLSS may possibly lead to exposure to microbial contaminants. It is recommended that the feasibility of an improved CLSS be assessed and implemented in light of the issues that are inherent in the use of T-CLSS in Afghanistan. Full article

In order to reach the Millennium Development Goals for significantly reducing the number of people without access to adequate sanitation, new holistic concepts are needed focusing on economically feasible closed-loop ecological sanitation systems rather than on expensive end-of-pipe technologies. An analysis of a former civilization in the Amazon (nowadays Brazil) highlights the possibility to close the loop with a more sustainable lifestyle integrating soil fertility, food security, waste management, water protection and sanitation, renewable energy. Terra Preta do Indio is the anthropogenic black soil produced by ancient cultures through the conversion of bio-waste, fecal matter and charcoal into long-term fertile soils. These soils have maintained high amounts of organic carbon several thousand years after they were abandoned. Deriving from these concepts, Terra Preta Sanitation (TPS) has been re-developed and adopted. TPS includes urine diversion, addition of a charcoal mixture and is based on lactic-acid-fermentation with subsequent vermicomposting. Lacto-fermentation is a biological anaerobic process that generates a pre-stabilization of the mixture. The main advantage of lacto-fermentation is that no gas and no odor is produced. What makes it particularly interesting for in-house systems even in urban areas. Instead, vermicomposting is an aerobic decomposition process of the pre-digested materials by the combined action of earthworms and microorganisms. It transforms the carbon and nutrients into the deep black, fertile and stable soil that can be utilized in agriculture. No water, ventilation or external energy is required. Starting from ancient Amazonian civilizations traditional knowledge, the aim of this work is to present TPS systems adopted nowadays. Full article