Search

The potential of co-digestion mixing thickened secondary sludge (TS) from extended aeration wastewater treatment plant and locally available substrates (whey, grease and septage) has been studied in this work, using three steps. The first step was a batch test to determine the biological methane potential (BMP) of different mixtures of the three co-substrates with TS. The second step was carried out with lab-scale reactors (20 L), simulating anaerobic continuous stirred tank reactors, fed by three mixtures of co-substrates that were determined according to the previous step results. Modeling was applied in the third step, using ADM1 as a mechanistic model to help understand the co-digestion process. According to the BMP step, septage used as a co-substrate has a negative effect on performance, and the addition of 10–30% grease or whey would lead to a gain of around 60–70% in the production of methane. The results from the reactor tests did not validate the positive effects observed with the BMP assay but confirmed good biodegradation efficiency (> 85%). The main purpose of co-digestion in this scenario is to recover energy from waste and effluents that would require even more energy for their treatment. The protein and lipid percentages of particulate biodegradable COD are important variables for digester stability and methane production, as predicted by modeling. The results of simulations with the ADM1 model, adapted to co-digestion, confirmed that this model is a powerful tool to optimize the process of biogas production.

Background: Faecal sludge (FS) represents a huge resource, which when tapped and made use properly can be of great benefit to many. However, the key to tapping this resource lies in proper characterisation, in order to make known the constituents and thereby determine the end-use. Methods: Three sources of FS from 43 communities in the Kumasi metropolis of Ghana were characterised in terms of their total solids content, chemical oxygen demand (COD), pH, nitrogen, phosphorous and lipid contents. FS from pit latrines, public septage and private septage were analysed. Results: On average, lipid content was found to be in the range of 8.82 – 9.66% of dry FS depending on the source of FS. Total solids were between 0.79 and 4.68%, while the COD was between 9495 and 45611mg/L. Phosphorus content was in the range of 137 – 520mg/L, while nitrogen was 649 – 4479mg/L. Most FS samples were generally alkaline in nature. Conclusions: These results are amongst the first long-term characterization efforts for FS in terms of conventional and non-conventional characteristics, tailored towards typical treatment and novel resource recovery options, respectively.

Paper presented at the ASEAN Conference on Environment-Behaviour Studies, 2010, Kuching, Sarawak,, Malaysia, 7-8 July. The management and treatment of sludge in developing countries, from on-site sanitation systems has neither been addressed by problem holders nor by researchers. All septic tanks need to be desludged regularly in order to maintain a certain level of treatment efficiency and minimize ecological and eventual marine pollution incidences. Practices followed in developing countries are discussed and lessons learned are emphasized for promoting a sustainable community development. Stakeholder identification and participation and their cooperation thorough the process, as well as new regulations on service provision and management rocedures are addresses in this study.

Background. In Ghana, faecal sludge (FS) from on-site sanitation facilities is often discharged untreated into the environment, leading to significant insults to environmental and human health. Anaerobic digestion offers an attractive pathway for FS treatment with the concomitant production of energy in the form of methane. Another innovative option includes separating digestion into acidogenesis (production of volatile fatty acids (VFA)) and methanogenesis (production of methane), which could ultimately facilitate the production of an array of biofuels and biochemicals from the VFA. This work describes the development, implementation and modeling based analysis of a novel multiphase anaerobic fermentation-digestion process aimed at FS treatment in Kumasi, Ghana. Methods. A pilot-scale anaerobic fermentation process was implemented at the Kumasi Metropolitan Assembly’s Oti Sanitary Landfill Site at Adanse Dompoase. The process consisted of six 10 m3 reactors in series, which were inoculated with bovine rumen and fed with fecal sludge obtained from public toilets. The performance of the fermentation process was characterized in terms of both aqueous and gaseous variables representing the conversion of influent organic carbon to VFA as well as CH4. Using the operating data, the first-ever process model for FS fermentation and digestion was developed and calibrated, based on the activated sludge model framework. Results and Conclusions. This work represents one of the first systematic efforts at integrated FS characterization and process modeling to enable anaerobic fermentation and digestion of FS. It is shown that owing to pre-fermentation of FS in public septage holding tanks, one could employ significantly smaller digesters (lower capital costs) or increased loading capabilities for FS conversion to biogas or VFA. Further, using the first-ever calibrated process model for FS fermentation and digestion presented herein, we expect improved and more mechanistically informed development and application of different process designs and configurations for global FS management practice.

The importance of faecal sludge management is gaining recognition. However, methods are still lacking to reasonably estimate the quantities and qualities (Q&Q) that need to be managed, which makes the planning for and implementing of management solutions quite difficult. The objective of this study was to collect and analyse Q&Q of faecal sludge at a citywide scale, and to evaluate whether "SPA-DET" data (=> spatially analysable demographic, environmental and technical) could then be used as predictors of Q&Q of faecal sludge. 60 field samples and questionnaires from Hanoi and 180 from Kampala were analysed. Software tools were used in an iterative process to predict total solids (TS) and emptying frequency in both Hanoi, Vietnam and Kampala, Uganda. City-specific data could be predicted with types of "SPA-DEr' data as input variables, and model performance was improved by analysing septic tanks and pit latrines separately. Individual models were built for TS concentrations and emptying frequency. In addition, a model was built across both cities for emptying frequency of septic tanks based on number of users and containment volume, indicating predictive models can be relevant for multiple cities. Number of users, containment volume, truck volume and income level were identified as the most common variables for the correction function. Results confirm the high intrinsic variability of faecal sludge characteristics, and illustrate the importance of moving beyond simple reporting of city-wide average values for estimations of Q&Q. The collected data and developed scripts have been made available for replication in future studies.

Summarization: Wastewater treatment facilities in tourist areas, in comparison to other municipal facilities, require specific configurations and additional management actions in order to achieve a reliable and cost-effective treatment. For example, the same facility operates during winter with minimum flows and in summer with peak flows. Moreover, careful effluent management is required to minimize environmental impact and health effects on tourists. In this study, effluent management data, including quantitative and qualitative effluent characteristics, reuse, and economic aspects of the Hersonissos Wastewater Treatment Plant (WTP) in Greece, are discussed. It has been designed to treat both municipal wastewater from the Hersonissos Municipality and septage from the wider area. Analysis of effluent quantitative data showed two flow peaks in the summer period and only one in winter. The WTP was found to provide a reliable level of treatment in terms of biochemical oxygen demand (95.9%), total suspended solids (97.2%), and total nitrogen (87.7%) removal, but increased numbers of fecal coliforms were measured at some peak flow periods, suggesting the need for additional management strategies. Effluent is reused mainly for agricultural irrigation; secondary uses include fire protection and landscape irrigation. Economic analysis showed that for each cubic meter treated, the total annual economic cost for treatment, filtration, and reuse infrastructure was 1.07 €, 0.05 €, and 0.08 €, respectively. Presented on: Environmental Management