An experimental study probing moisture kinetics and indices of microwave dried fecal sludge with an insight on real world applications

The effect of microwave output power and sample amount on effective moisture diffusivity were investigated using microwave drying technique on round okra (Hibiscus esculentus L.). The various microwave output powers ranging from 180 to 900 W were used for the determination of effective moisture diffusivity for constant sample amount of 100 g okra. To examine the effect of sample amount on effective moisture diffusivity, the samples in the range of 25–100 g were dried at constant microwave output power of 360 W. By increasing the microwave output powers and decreasing the sample amounts, the effective moisture diffusivity values ranged from 20.52 × 10−10 to 86.17 × 10−10 and 34.87 × 10−10 to 11.91 × 10−9 m2/s−1, respectively. The modeling studies were performed to illustrate the relationship between the ratio of the microwave output power to sample amount and effective moisture diffusivity. The relationship between drying constant and effective moisture diffusivity was also estimated.

A financial comparison of a parallel sewer based (SB)system withactivated sludge, and a fecal sludge management (FSM) system withonsite septic tanks, collection and transport (C&T) trucks, anddrying beds was conducted. The annualized capital for the SB ($42.66capita–1 year–1) was ten timeshigher than the FSM ($4.05 capita–1 year–1), the annual operating cost for the SB ($11.98 capita–1 year–1) was 1.5 times higher than the FSM ($7.58capita–1 year–1), and the combinedcapital and operating for the SB ($54.64 capita–1 year–1) was five times higher than FSM ($11.63capita–1 year–1). In Dakar, costsfor SB are almost entirely borne by the sanitation utility, with only6% of the annualized cost borne by users of the system. In additionto costing less overall, FSM operates with a different business model,with costs spread among households, private companies, and the utility.Hence, SB was 40 times more expensive to implement for the utilitythan FSM. However, the majority of FSM costs are borne at the householdlevel and are inequitable. The results of the study illustrate thatin low-income countries, vast improvements in sanitation can be affordablewhen employing FSM, whereas SB systems are prohibitively expensive.

In the faces of alarming urbanization and the high demand for basic sanitation, there are debts that urban sanitation in Sub-Saharan Africa has been steadily improving in one hand and worsening on the other hand in the recent decades. The objective of this research was to investigate the status of urban sanitation coverage in relation to Millennium Development Goal (MDG) 2015 target and the major gaps of fecal sludge management (FSM) system. For this purpose, we conducted the sanitation coverage survey in the urban slums of Addis Ababa and we compared it with the nationwide sanitation inventory conducted by Ethiopian Minister of Water, Irrigation and Energy (EMWIE) in 2014. The results revealed that only 11.4% of urban slum residents have access to improved sanitation. This sanitation coverage is by far lower than the improved sanitation coverage of the capital city (41.2%) and the national urban sanitation coverage (27%). Open defecation being a common practice in urban areas of Ethiopia accounts 8.2%, 5.8% and 8.0% for urban slums of the capital and all urban areas of the country respectively. Despite the increasing trend in urban sanitation coverage in Ethiopia, it is far from the MDG target and the majority of urban residents are living under severe health and environmental risks. The urban poor are the ones mainly excluded from the basic sanitation services. Most sanitation facilities (about 91%) in Addis Ababa are onsite sanitation that requires pit emptying nevertheless 85.4% of the residents dissatisfied with the pit emptying services. As results of the severe constraints of pit emptying and FSM services, most toilet facilities (about 50%) were full. The FSM system is totally ineffective to tackle environmental pollution and public health risks. This calls an urgent action towards the development of integrated FSM system that ensures environmental safety and targets valorization of human waste

In striving to achieve sustainable sanitation, one challenge is to ensure hygienic disposal of faecal sludge from on-site sanitation facilities. In order to safely dispose of the sludge, drying can be carried out to reduce the volume and mass of the waste for transportation, to deactivate pathogens making the sludge safer to handle and reuse, and finally to increase the calorific value of the sludge for potential fuel use. Improved understanding of the drying process and kinetics are crucial for the design of treatment facilities for faecal sludge and the quickest way to do this is to perform drying analysis of faecal sludge in laboratory small scale set-up. In this study, faecal sludge from ventilated improved pit (VIP) latrines from the Durban area in South Africa were dried in a convective drying thermobalance by varying the drying temperature from 40 to 80oC, the relative humidity from 0 to 25% and the velocity of the supplied air from 0.3 to 1.2 mm/s. The faecal sludge samples were in the form of a thin layer or pellets with different diameters from 8 to 14 mm. Drying curves were plotted from the experimental data and used to determine the drying rates, critical moisture content and effective diffusivities of moisture through the faecal sludge with their respective activation energies. The drying curves data were then fitted to various common models from literature, and a faecal sludge drying model was developed from this analysis. Drying rates were in the range between 1 and 40 g/min/m2, increasing as temperature and air velocity were increased, and pellet diameter and relative humidity decreased. Temperature and pellet diameter had the greatest influence on the drying rate, whereas the drying kinetics were affected in a moderate way by the relative humidity, and insignificantly by the air velocity under the explored conditions. The effective diffusivities increased from 7.81 x 10-8 to 1.97 x 10-7 m2 /s by increasing temperature from 40° to 80°C, with an activation energy of humidity. The experimental data fitted most closely to the Page model and, based on the latter, a new model was proposed for the prediction of drying times across a range of temperatures and pellet diameters. The results of the proposed model fitted the experimental data with acceptable accuracy, so that the developed model could be employed as an analytical tool for the design, operation and optimisation of drying equipment.

Design of treatment plants for faecal sludge management systems relies on a comprehensive accurate knowledge of FS (faecal sludge) characteristics, but this information is lacking. Developing countries like Ghana, where large proportion of the urban population (Accra) rely on onsite sanitation systems, face a lot of FSM (faecal sludge management) design challenges as a result of lack of a comprehensive study data on physicochemical characteristics of raw faecal sludge after primary dewatering. Achieving a fully operational FSM chain would imply a well understanding of the characteristics of the FS and its dynamics after primary dewatering. A study was carried out to determine the characteristics of faecal sludge brought to the Lavender Hill treatment plant, Accra Metropolis, and environs to ensure the treatability and uses of the products after treatment. The treatment plant receives an average of 150 trucks (1350m3) a day with 58% coming from private homes and 42% from public toilets. Composite samples were made from both public and private toilets facilities. Samples were taken from a reservoir holding faecal sludge from both public and private facilities, examined on daily basis and characterized. The values obtained showed high concentrations of BOD and COD values. The COD: BOD ratios showed that the faecal sludge is not stabilized yet and can be further degraded. The calorific value for the dry sludge was found to be 15.16-15.82 MJ/kg and 16.39–18.31 MJ/kg for the wet sludge. The calorific value of the sludge is adequate enough to be used as potential feedstock for green energy generation. The high concentrations of COD and organic matter of the faecal sludge make it suitable enough for biogas generation. A good correlation (r=0.909,R2=82.6%) between the calorific value and the TVS was found to be CV=0.122TVS+7.44. Heavy metal concentrations were low and satisfied the EPA Ghana guidelines for sludge. Thus products from the treatment can be used for agricultural purposes.

The study aimed to assess the influence resource planning influences the implementation of a faecal sludge management system in Embu County between March and December 2022, adopting a descriptive research design. The population included 655 individuals, with a sample size determined using Taro Yamane's formula for landlords and a census method for top managers, technical officers, contractors, and individuals involved in exhausting. Research instruments comprised scheduled questionnaires and interviews, with ethical considerations obtained from relevant authorities. Data analysis utilized SPSS Version 26 for both qualitative and quantitative data, employing thematic analysis for qualitative data and descriptive and inferential analyses for quantitative data. Findings revealed a notable gender imbalance and age-related impacts on perceptions in fecal sludge management. Resource planning effectiveness indicated strengths in objective setting, communication, and risk management, significantly influencing system implementation. Recommendations include strengthening the strategic framework, enhancing vision and mission statements, refining financial planning, addressing role comprehension gaps, aligning resource planning with project timelines, and implementing regular monitoring and evaluation for ongoing improvements. Overall, the study emphasizes the pivotal role of resource planning in the success of fecal sludge management projects and highlights areas for improvement to enhance effectiveness.

Ginger rhizomes of different thickness, microwave output power and sample load were dehydrated in a modified microwave oven, and effective moisture diffusivity was calculated. Among the various basic models considered, diffusion equation was most suitable to predict the drying behavior for the process conditions. Based on the interpretations, the constants and coefficients were rewritten in Arrhenius and logarithmic expressions for microwave power. The derived mathematical models were validated according to statistical parameters, viz. reduced chi-square, root mean square error, mean bias error and t-test values. The modified diffusion model explained the suitability of thin layer microwave drying behavior of ginger rhizome slices, yielding the highest R2 of 0.9983. The effect of microwave drying on extraction of oleoresins with hexane as the solvent was in the range of 2.53–4.55%. Scanning electron microscopy and Fourier transform infrared spectroscopy revealed enhanced integrity of texture and functional groups by microwave treatment. PRACTICAL APPLICATIONS Drying, a process of removal of moisture content, was carried out on ginger rhizomes. Besides several advantages during dehydration, some important changes take place, such as structural and physicochemical modifications, which affects the final product quality. Microwave heating at specific experimental conditions was aimed at the restoration of nutritional and medicinal properties of the raw material. Mathematical models applied in this research will be helpful to analyze, simulate as well as to design and scale up the microwave drying process for industrial and commercial applications. Furthermore, the product may have an increased shelf life, finished product quality; may reduced energy cost in comparison with the conventionally dried rhizomes; and may serve as ingredient for medicinal, pharmaceutical and cosmetics industry for the extraction of essential oils such as oleoresins.

Analysis of energy consumption, heat and mass transfer, drying kinetics and effective moisture diffusivity during foam-mat drying of mango in a convective hot-air dryer

Comprehensive knowledge of faecal sludge characteristics is needed for sludge management planning, but it is lacking for the city of Phnom Penh, Cambodia. Thus, this study characterised physicochemical properties of faecal sludge from households in Phnom Penh and related these to sludge containment unit type, unit age, connectedness to the urban drainage network, type of wastewater captured, watertight containment units, number of users, and emptying practices. In total, 194 faecal sludge samples collected during containment unit emptying were analysed for physicochemical parameters. Information on containment units was collected in a survey of emptiers and users. Mean values of faecal sludge chemical parameters were found to be slightly lower than previously reported values for low-/middle-income countries, whereas physicochemical properties were within similar ranges. The main factor influencing organic matter content in faecal sludge was containment unit connection to the urban drainage network, whereas emptying practice and capture of only blackwater affected nutrient levels. The concentrations of nutrients and organic pollutants greatly exceeded Cambodian discharge standards for wastewater. This causes environmental impacts, so treatment is needed before discharge. The faecal sludge characteristics and influencing factors identified here can serve as a baseline for sanitation stakeholders planning faecal sludge management systems in Phnom Penh and similar cities.

Design and performance evaluation of convective drier and prediction of drying characteristics of potato under varying conditions

Re-using faecal sludge (FS) to generate value has the potential to contribute towards solving the issue of long term sanitation solutions in growing urban areas across sub-Saharan Africa; however, hitherto, no design tools have been available that are capable of simulating a system involving economic factors, complex social issues and environmental circumstances. We hypothesized that Agent-Based Modelling (ABM), when deployed with appropriate rigour, can provide such a tool. Extensive field work was carried out in a Malawian city, investigating the adoption of Skyloo above-ground composting toilets by households, and the operation of the municipal FS site. 65 semi-structured interviews and 148 household interviews, together with observations, were carried out to characterize these processes, with the data acquired being used to construct two separate ABMs. The Skyloo ABM was run for various scenarios of start-up capital for business and payback of loans against the toilet cost to households. The municipal FS Site ABM was run for different patterns of dumping fee and enforcement structure. The field work demonstrated that there is potential for further expansion of FS reuse, with a market for agricultural application. The Skyloo ABM identified the significance of start-up capital for a business installing the toilet technology; the municipal FS Site ABM showed that existing fees, fines and regulatory structure were insufficient to reduce illegal dumping of FS to any useful degree, but that a monthly permit system would provide enhanced revenue to the city council compared with per-visit charging of disposal companies at the municipal FS site. Whilst each ABM ideally requires some additional data before full application, we have, for the first time, shown that ABM provides a basis for the simulation-based design of FS management systems, including complex social, economic and environmental factors.

In the present study, tea leaves (Camellia sinensis) were dried in the domestic microwave oven in order to determine the effect of microwave output power and sample amount on moisture ratio, drying time and effective moisture diffusivity. Five different microwave output power (180-900 W) and five different sample amount (20-100 g) values were used in the drying experiments. The drying data were fitted to some empirical and semi empirical models in order to determine the kinetic parameters. Among of the models proposed, the Page model gave a better fit for all drying conditions applied. The effective moisture diffusivity values were calculated by using the method of slopes at various microwave output powers and sample amounts. Moreover, the activation energy was calculated using an exponential expression based on Arrhenius equation.

The achievement of safe sanitation access is about 7.42 % in 2018, that indicates high risk of faecal contamination from unmanaged onsite sanitation system and has not been fully supported by faecal sludge service. This paper described the study of characteristic of onsite sanitation and faecal sludge for review potential of integrating of sludge handling with improved communal wastewater treatment. Faecal sludge quality were observed from pit latrines and communal septic tank, then analysis method apply cluster analysis and through close loop approach consider treatment and disposal for resource recovery. The pilot model of combined treatment of wastewater and faecal sludge was developed by anaerobic digester with a maximum 5% sludge loading, then further treatment by biofilter system and sludge drying bed. The quality of treated water can meet COD and nitrogen as effluent standard, biosolid reached a stabilization index of 40 - 60%, water content of 50-60% and less Coliform bacteria content. The characteristics of faecal sludge strength to be handled will be influenced bytechnical aspect or environment. The integrated system could be applied to manage wastewater and faecal sludge and its by products, mainly for rural area has not been catered by faecal sludge service.

The race of attaining adequate sanitation services by 2030 remains a myth in Tanzania since the faecal sludge management systems lags far behind wastewater management systems. The case should have been vice-versa since massive amount of faecal sludge is generated in urban settings as compared to wastewater. There are several setbacks that lead to the cause but this study explored the relevance of available policies, acts, regulations, guidelines, rules and standards in attaining adequate faecal sludge management in urban settings, taking Arusha city as a reference point for discussion. The review of legally binding document and key informant interviews were the methods used for data collection

This document is the final technical report from the project OPP164143, entitled "Characterization of faecal material behavior during drying". EXECUTIVE SUMMARY Drying is a relevant unit operation during faecal sludge and fresh faeces treatment. It allows the removal of moisture from the faecal matter and its disinfection, so making it safer to handle, easier to transport and a more suitable biofuel. The Pollution Research Group (PRG), at the University of KwaZulu-Natal (UKZN), received a grant from the Bill & Melinda Gates Foundation through the OPP1164143 to investigate the drying of faecal materials (faecal sludge from onsite sanitation facilities and fresh faeces). The objectives of this research were to generate useful insight and data to overcome the current technological gaps from faecal wastes drying. This research project, done in collaboration with Swansea University and Cranfield University. This research project was divided into three distinct phases: (i) a landscape study, (ii) experimental work, (iii) and dissemination of knowledge and data. The landscape study was conducted to identify the gaps in the drying technologies and the areas of greatest interest to explore through research. The experimental planning was based on the outcomes from the landscape study, and different kinds of experiments were carried in the three institutions. The next step was to disseminate the data and knowledge generated from this project, as well as data collected from previous projects and partner institutions. The objectives from the experimental work included topics as: drying kinetics, heat of drying, boundedness of the moisture in the faecal material, thermal degradation, pathogens deactivation, physiochemical properties, morphological characteristics, boundedness of the moisture, odours. The experimental work from this project was carried out in three different geographical locations: PRG-UKZN, Cranfield University and Swansea University. The experiments were conducted using faecal sludge collected from on-site sanitation facilities from the eThekwini municipality (faecal sludge from ventilated pit latrines, urine-diverting dry toilets and an anaerobic baffled reactor from a decentralized water treatment system), as well as fresh Human faeces from donations at PRG-UKZN and Cranfield University. The faecal sludge samples from on-site sanitation facilities were exported to the United Kingdom (UK) for their testing at Cranfield University and Swansea University. The experimental work included the following analysis: thermogravimetry, thermal analysis, gas analysis, spectrophotometry, calorimetry, proximate composition analysis, CNS analysis, rheometry, dewatering, sorption isotherms, water activity analysis, thermal properties analysis, specific surface analysis, particle size distribution analysis, qualitative observations. The outcomes from this research project highlight the importance of temperature on the drying kinetics and disinfection of the faecal matter. Moreover, the moisture boundedness at the different stages from the drying process was characterized and related to the variation of the faecal matter consistency, energy consumption, thermal properties and pathogens deactivation. Furthermore, the different types of faecal material were compared in terms of their drying and dewatering capabilities, and moisture boundedness. In addition to this, interesting results were obtained concerning the thermodynamic equilibrium of the process, properties of the dried solid, the suitability of radiative methods to dry faecal matter and the odour emission.