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The study investigated the effects of long-chain fatty acids (LCFA) on anaerobic sludge treating lipid-rich wastewater. It involved batch experiments with three sludge samples: two acclimated to lipids and one non-acclimated. The experiments aimed to observe the degradation of LCFA, specifically oleate and palmitate, by dosing them at concentrations ranging from 50 to 600 mg/L. Measurements of the cumulative methane production and the LCFA concentration, quantified as fat, oil, and grease (FOG) were performed. To ensure the sludge was free from other biodegradable substrates, part of the samples was pre-incubated without feed. The tests were conducted with both pre-incubated and non-incubated inoculum sludge. The findings revealed that oleate was degraded more efficiently than palmitate across all sludge samples, with a greater conversion rate to methane. Sludge samples acclimated to lipids showed a superior capacity to degrade LCFA compared to non-acclimated ones. It was noted that at concentrations above 400 mg/L, the conversion of LCFAs to intermediate compounds was inhibited, although this did not affect the subsequent methane production. The study concludes with a recommendation for sludge adaptation strategies to boost the efficiency of anaerobic wastewater treatment systems dealing with lipid-rich waste. The presence of LCFA-degrading bacteria families like Kosmotogaceae, Petrotogaceae, and Synergistaceae in the acclimated sludge samples underscores the adaptation and potential for improved degradation performance.

Flooding is expected to increase due to climate change, urbanisation, and land use change. To address this issue, Nature-Based Solutions (NBSs) are often adopted as innovative and sustainable flood risk management methods. Besides the flood risk reduction benefits, NBSs offer co-benefits for the environment and society. However, these co-benefits are rarely considered in flood risk management due to the inherent complexities of incorporating them into economic assessments. This research addresses this gap by developing a comprehensive methodology that integrates the monetary analysis of co-benefits with flood risk reduction in economic assessments. In doing so, it aspires to provide a more holistic view of the impact of NBS in flood risk management. The assessment employs a framework based on life-cycle cost-benefit analysis, offering a systematic and transparent assessment of both costs and benefits over time supported by key indicators like net present value and benefit cost ratio. The methodology has been applied to the Tamnava basin in Serbia, where significant flooding occurred in 2014 and 2020. The methodology offers valuable insights for practitioners, researchers, and planners seeking to assess the co-benefits of NBS and integrate them into economic assessments. The results show that when considering flood risk reduction alone, all considered measures have higher costs than the benefits derived from avoiding flood damage. However, when incorporating co-benefits, several NBS have a net positive economic impact, including afforestation/reforestation and retention ponds with cost-benefit ratios of 3.5 and 5.6 respectively. This suggests that incorporating co-benefits into economic assessments can significantly increase the overall economic efficiency and viability of NBS.

In recent decades, there has been a growing focus on the management and valorization of digestate, primarily driven by its nutrient-rich composition, which positions it as a promising resource for biofertilizer production. However, several countries still restrict the direct application of digestate due to its potential environmental hazard, which includes the presence of contaminants of emerging concern (CECs) such as pharmaceuticals. This paper explores the efficacy of a novel UV/ozone-based technology, UVOX Redox®, in removing prevalent pharmaceuticals, including antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs), from the digestate of two biogas plants. In both cases, UVOX showed to be a feasible solution for pharmaceutical removal from digestate. Addition of hydrogen peroxide further increased the process efficiency, achieving > 90% removal of all compounds within an hour. The energy per order (EEO) value for all the studied pharmaceuticals was less than the reported median EEO for O3 and UV treatment, showcasing notable energy efficiency in UVOX technology. Moreover, the research highlights that the presence of ions augments the removal efficiency when applying the UVOX technology. In addition, the research results revealed a significant correlation between the effectiveness of the UVOX technology and UV transmittance, with R² exceeding 90% for pharmaceuticals and 75% for Dissolved Organic Carbon (DOC). This finding suggests that UV transmittance can serve as a viable surrogate method for implementing this advanced oxidation process in practical applications.

Ca. Accumulibacter was the predominant microorganism (relative FISH bio-abundance of 67 ± 5%) in a lab-scale sequential batch reactor that accomplished enhanced biological phosphorus removal (EBPR) while using glucose and acetate as the carbon sources (1:1 COD-based ratio). Both organic compounds were completely anaerobically consumed. The reactor's performance in terms of P/C ratio, phosphorous release and uptake, and overall kinetic and stoichiometric parameters were on the high end of the reported spectrum for EBPR systems (100:9.3 net mg phosphate removal per mg COD consumed when using glucose and acetate in a 1:1 ratio). The batch tests showed that, to the best of our knowledge, this is the first time a reactor enriched with Ca. Accumulibacter can putatively utilize glucose as the sole carbon source to biologically remove phosphate (COD:P (mg/mg) removal ratio of 100:6.3 when using only glucose). Thus, this research proposes that Ca. Accumulibacter directly anaerobically stored the fed glucose primarily as glycogen by utilizing the ATP provided via the hydrolysis of poly-P and secondarily as PHA by balancing its ATP utilization (glycogen generation) and formation (PHA storage). Alternative hypotheses are also discussed. The reported findings could challenge the conventional theories of glucose assimilation by Ca. Accumulibacter, and can be of significance for the biological removal of phosphorus from wastewaters with high contents of fermentable compounds or low VFAs.

Background: In recent years the number of tools developed to help advance sustainable urban sanitation coverage in low- and middle-income countries has increased significantly, yet no study has been undertaken to determine their usage or impact. This paper explores the usage and impact of four urban sanitation tools: Shit flow Diagram (SFD), City Service Delivery Assessment (CSDA), SaniPath, and the Citywide Planning Tool. Methods: A mixed methodology approach was used which included a questionnaire (n = 87) and interviewing the tools developers (n = 5) and users (n = 25). Results and discussion: There was a high awareness of three of the tools (86%, n = 87), but relatively low usage (53%, n = 87). The questionnaire respondents and interviewees confused the Citywide Planning Tool with other tools, so no usage was found. The CSDA and SaniPath were being used beyond the groups that developed them and by their targeted group, but the main users were found to be researchers in academia. There was evidence that SFDs and CSDAs were evolving beyond their original scope, which was attributed to their use in academia. Their use in academia should not be dismissed as they may lead to future usage and impact. Although impact will take time and it is difficult to directly attribute impact to a specific tool, evidence of the impact of the SFD and SaniPath was found. This impact demonstrates how these tools can lead to improvements in urban sanitation. This study also highlights the need for further research into the drivers of tool usage.

Digestate is a rich source of nutrients that can be applied in agricultural fields as fertilizer or irrigation water. However, most of the research about application of digestate have focused on its agronomic properties and neglected the potential harm of the presence of contaminants of emerging concern (CECs). Aadvanced oxidation processes (AOPs) have proved to be effective for removing these compounds from drinking water, yet there are some constrains to treat wastewater and digestate mainly due to their complex matrix. In this study, the feasibility to remove different CECs from digestate using O3 and O3/H2O2 was assessed, and the general effect of the matrix in the oxidation was explained. While the lab-scale ozonation provided an ozone dose of 1.49 mg O3/mg DOC in 5 h treatment, almost all the compounds were removed at a lower ozone dose of maximum 0.48 mg O3/mg DOC; only ibuprofen required a higher dose of 1.1 mg O3/mg DOC to be oxidized. The digestate matrix slowed down the kinetic ozonation rate to approximately 1% compared to the removal rate in demineralized water. The combined treatment (O3/H2O2) showed the additional contribution of H2O2 by decreasing the ozone demand by 59–75% for all the compounds. The acute toxicity of the digestate, measured by the inhibition of Vibrio fisheries luminescence, decreased by 18.1% during 5 h ozonation, and by 34% during 5 h O3/H2O2 treatment. Despite the high ozone consumption, the ozone dose (mg O3/mg DOC) required to remove all CECs from digestate supernatant was in the range or lower than what has been reported for other (waste-)water matrix, implying that ozonation can be considered as a post-AD treatment to produce cleaner stream for agricultural purposes.

For over 10 years, citywide sanitation plans have been developed, and now, citywide inclusive sanitation is being piloted globally, yet no tools exist to monitor changes in sanitation at a citywide level. This paper explores the use of Shit Flow Diagram Graphics (SFDGs) and City Service Delivery Assessments (CSDAs) to monitor changes in sanitation at a citywide level. This was done by documenting the changes in sanitation from 2015 to 2019 in Tiruchirappalli, India, and developing SFDGs and CSDAs for those years. The changes in the SFDGs and CSDAs were then compared with the documented changes. The SFDGs captured all changes in service delivery that affected >1% of the population, and all of the interventions in the enabling environment change in terms of appropriateness, acknowledgment, or implementation were captured by the CSDAs. Therefore, units of both tools were assessed to be appropriate for monitoring purposes. Using these tools to monitor change was complex and tedious, and this was improved by the development of Trend Graphs and Citywide CSDAs. This paper highlights the potential of Trend Graphs and Citywide CSDAs to monitor sanitation at a citywide level. Additionally, this is the first paper to attempt to monitor changes in sanitation holistically at a citywide level.

This study evaluated the effects of sludge retention time (SRT) on the membrane filtration performance of an anaerobic membrane bioreactor (AnMBR) fed lipid-rich synthetic dairy wastewater. The membrane filtration performance was evaluated in two AnMBR systems operated at two different SRTs, i.e., 20 and 40 days. For the AnMBR operated at 40 days, SRT exhibited worse membrane filtration performance characterized by operational transmembrane pressures (TMP) exceeding the maximum allowed value and high total resistances to filtration (Rtotal). The sludge in the two reactors evaluated at the different SRTs showed similar sludge filterability properties. However, the sludge in the reactor operated at 40 days SRT was characterized by exhibiting the highest concentrations of: (i) total suspended solids (TSS), (ii) small-sized particles, (iii) extracellular polymeric substances (EPS), (iv) soluble microbial products (SMP), (v) fats, oils and grease (FOG), and (vi) long-chain fatty acids (LCFA). The cake layer resistance was the major contributor to the overall resistance to filtration. The high TSS concentration observed in the AnMBR systems apparently contributed to a less permeable cake layer introducing a negative effect on the membrane filtration performance.

Thermal drying is an effective sludge treatment method for dealing with large volumes of sludge. Microwave (MW) technology has been proposed as an effective and efficient technology for sludge drying. The physical-chemical properties of the sludge depend both on the origin of the sludge, as well as on the treatment process at which the sludge has been exposed. The physical-chemical properties of the sludge affect the performance and the subsequent valorisation and management of the sludge. This study evaluated the effect of certain physical-chemical properties of the sludge (moisture content, organic content, calorific value, porosity, hydrophobicity, and water-sludge molecular interaction, among others) on the MW sludge drying and energy performance. Four different types of sludge were evaluated collected from municipal wastewater treatment plants and septic tanks. The performance of the MW system was assessed by evaluating the sludge drying rates, exposure times, energy efficiencies and power input consumed by the MW system and linking the MW drying performance to the sludge physical-chemical properties. The results confirmed that MW drying substantially extends the constant drying period associated with unbound water evaporation, irrespective of the sludge sample evaluated. However, the duration and intensity were determined to depend on the dielectric properties of the sludge, particularly on the distribution of bound and free water. Sludge samples with a higher amount of free and loosely bound water absorbed and converted MW energy into heat more efficiently than sludge samples with a lower amount of free water. As a result, the sludge drying rates increased and the constant drying rate period prolonged; hence, leading to an increase in MW drying energy efficiency. The availability of free and loosely bound water molecules was favoured when hydrophobic compounds, e.g., oils and fats, were present in the sludge.

The provision of effective sanitation strategies has a significant impact on public health. However, the treatment of septic sludge still presents some challenges worldwide. Consequently, innovative technologies capable of an effective and efficient sludge treatment, mostly at a decentralized level, are in high demand to improve sanitation provision. To address this problem, this study evaluates a novel semi-decentralised mobile faecal sludge treatment system, the pilot-system for which consists of a combination of several individual processes including mechanical dewatering (MD), microwave (MW) drying, and membrane filtration (ultrafiltration [UF] and reverse osmosis [RO]). The system evaluation was carried out by treating raw, partially digested faecal sludge (FS) from septic tanks—hence, septic sludge (SS)—in the Jordan Valley, Jordan. The pilot-scale system exhibited an effective and flexible treatment performance for (i) sanitizing faecal sludge and related liquid streams (MW and UF); (ii) reducing the treated sludge mass (and sludge volume) (MD and MW); and (iii) producing a high-quality treated liquid stream ideal for water reclamation applications (UF and RO). The MD process removed approximately 99% of the initial SS water content. The MW drying system completely removed E. coli and dehydrated the dewatered sludge at low energy expenditures of 0.75 MJ kg−1 and 5.5 MJ kg−1, respectively. Such energy expenditures can be further reduced by approximately 40% by recovering energy in the condensate and burning the dried sludge, which can then be reused inland applications. The membrane filtration system (UF and RO) was able to produce high-quality treated water that is ideal for the water reuse applications that irrigation requires, as well as meeting the Jordanian standard 893/2006. In addition, the system can also be powered by renewable energy sources, such as photovoltaic energy. Therefore, this research demonstrates that the evaluated semi-decentralised mobi

To achieve SDG 6.2.1 (a) on safely managed sanitation services, several financial flow models (FFMs) and business models for the sanitation value chain have been implemented in Bangladesh and elsewhere; however, there is limited research on financial viability and sustainability of business models. Bangladesh has attained 99% sanitation coverage, mostly with onsite sanitation systems; however, the country is facing a second-generation sanitation challenge, fecal sludge management, encompassing the entire sanitation chain. Kushtia Municipality in Bangladesh is entirely served by onsite systems; the fecal sludge emptying service is provided by the municipality, and the fecal sludge treatment plant is managed by a private entity. This study investigated sustainability of FFMs in Kushtia by using the financial, institutional, environmental, technical, and social (FIETS) sustainability approach and applying the financial flow simulator (eSOSView™) tool to analyze financial viability. Several criteria in each aspect of the FIETS approach were developed, scored, and validated by stakeholders to determine sustainability. The study found that the financial aspect is the most important criteria for sustainability and “modified parallel tax and discharge fee” is the most sustainable business model for Kushtia.

Although faecal sludge (FS) co-compost contains vital nutrients, there are several barriers limiting adoption and reuse of FS co-compost in agriculture. This study in Bhubaneswar found that health risk and bad odour were the two topmost negative perceptions of FS co-compost reuse. The main factors influencing farmers’ negative perceptions of FS co-compost were bad odour and fear of infection, whereas socio-cultural/religious beliefs and bad odour were the key factors influencing the negative perceptions of urban households practising kitchen gardening (UHPKG). Fear of infection and bad odour were the key factors influencing fertiliser retailers’ negative perceptions, while inadequate information, unavailability, and lack of government policy on FS co-compost reuse were the key factors influencing Farmer Producer Organisations’ negative perceptions. The majority of farmers (95%) and UHPKG (72%) were unwilling to consume food crops grown with FS co-compost, mainly because of feelings of disgust, fear of infection, and religious and socio-cultural beliefs.

Various business models for fecal sludge emptying and transport have been developed to address challenges and their advantages have been documented; however, their evaluation has not been investigated. This study developed an evaluation framework, which was tested in informal settlements in Kampala for sustainable business models of fecal sludge emptying and transport. Through key informant interviews and stakeholder consultations, service delivery challenges from informal settlements in Kampala were identified and included in the framework, which were: high cost of emptying services, spillages, access to facilities, high operational costs and social stigma. The evaluation framework adopted six service criteria: Financial, Institutional, Environmental, Technological, Social and Scalability; these were further defined by fifteen service sub-criteria. The criteria were tested separately on eight business models—for mechanized (cesspool) and semi-mechanized (gulper) technologies. The key output of the evaluation framework (business model scorecard) revealed that two models (scheduled desludging and call center) for cesspool technology and three models (mobile transfer stations, scheduled desludging and call center) for gulper technology have high potential for service improvement in informal settlements. Scheduled desludging and mobile transfer stations can effectively optimize emptying services and subsequently reduce emptying charges, whereas the call center is critical for bridging service delivery.

Photo-activated sludge (PAS) systems are an emerging wastewater treatment technology where microalgae provide oxygen to bacteria without the need for external aeration. There is limited knowledge on the optimal conditions for enhanced biological phosphorus removal (EBPR) in systems containing a mixture of polyphosphate accumulating organisms (PAOs) and microalgae. This research aimed to study the effects of substrate composition and light intensity on the performance of a laboratory-scale EBPR-PAS system. Initially, a model-based design was developed to study the effect of organic carbon (COD), inorganic carbon (HCO3) and ammonium-nitrogen (NH4-N) in nitrification deprived conditions on phosphorus (P) removal. Based on the mathematical model, two different synthetic wastewater compositions (COD:HCO3:NH4-N: 10:20:1 and 10:10:4) were examined at a light intensity of 350 µmol m−2 sec−1. Add to this, the performance of the system was also investigated at light intensities: 87.5, 175, and 262.5 µmol m−2 sec−1 for short terms. Results showed that wastewater having a high level of HCO3 and low level of NH4-N (ratio of 10:20:1) favored only microalgal growth, and had poor P removal due to a shortage of NH4-N for PAOs growth. However, lowering the HCO3 level and increasing the NH4-N level (ratio of 10:10:4) balanced PAOs and microalgae symbiosis, and had a positive influence on P removal. Under this mode of operation, the system was able to operate without external aeration and achieved a net P removal of 10.33 ±1.45 mg L−1 at an influent COD of 100 mg L−1. No significant variation was observed in the reactor performance for different light intensities, indicating the EBPR-PAS system can be operated at low light intensities with a positive influence on P removal.

Sewage sludge management and treatment can represent up to approximately 30% of the overall operational costs of a wastewater treatment plant. Microwave (MW) drying has been recognized as a feasible technology for sludge treatment. However, MW drying systems exhibit high energy expenditures due to: (i) unnecessary heating of the cavity and other components of the system, (ii) ineffective extraction of the condensate from the irradiation cavity, and (iii) an inefficient use of the microwave energy, among others issues. This study investigated the performance of a novel pilot-scale MW system for sludge drying, specifically designed addressing the shortcomings previously described. The performance of the system was assessed drying municipal centrifuged wasted activated sludge at MW output powers from 1 to 6 kW and evaluating the system's drying rates and exposure times, specific energy outputs, MW generation efficiencies, overall energy efficiencies, and specific energy consumption. The results indicated that MW drying significantly extends the duration of the constant rate drying period associated with the evaporation of the unbound sludge water, a phase associated with low energy input requirement for evaporating water. Moreover, the higher the MW output power, the higher the sludge power absorption density, and the MW generation efficiency. MW generation efficiencies of up to 70% were reported. The higher the power absorption density, the lower the chances for energy losses in the form of reflected power and/or energy dissipated into the MW system. Specific energy consumptions as low as 2.6 MJ L−1 (0.74 kWh L−1) could be achieved, well in the range of conventional thermal dryers. The results obtained in this research provide sufficient evidence to conclude that the modifications introduced to the novel pilot-scale MW system mitigated the shortcomings of existing MW systems, and that the technology has great potential to effectively and efficiently drying municipal s

A majority of the world's population use onsite sanitation systems, which store or treat excreta close to where it is generated. Sludge from these systems needs to be managed through a series of stages, known as the sanitation value chain. There is a huge diversity of service providers, not only within each part of the chain, but also along the chain bridging the different components. These service providers are linked not only by the flow of materials, but also by the transfer of money. Therefore for this system to be considered financially sustainable all services from the toilet to reuse or disposal need to be considered. A tool has been developed (eSOSView™) to simulate, evaluate, and optimise the financial flows along and within the sanitation value chain. In this paper eSOSView™ was tested, validated (using existing data), and piloted (including data collection). This paper demonstrates how eSOSView ™ can be used to evaluate different financial flow models, to assess financial sustainability in different parts of the sanitation value chain and optimise the financial sustainability along the sanitation value chain.

Sanitation infrastructure are not able to cope with the increasing population in low-income countries, which leaves populations exposed to faecal contamination from multiple pathways. This study evaluated public health risk (using SaniPath) in a low-income community during the dry season, to identify the dominant exposure pathways, and compare this data to existing data for the rainy season, questioning the assumption that risk of faecal contamination is higher in the rainy season. SaniPath was used to collect and assess exposure and environmental data, and to generate risk profiles for each pathway. In the dry season the highest exposure frequency was for bathing and street food, exposure frequency generally increased, and seasonal variation was found in five pathways. The highest hazards in the dry season were through contact with drains, soil, and street food. Seasonal variation was found in the contamination of open drains and street food, with higher levels of Escherichia coli (E. coli) in the dry season. Open drains were identified as the most dominant risk pathway in both seasons, but risk was higher in the dry season. This highlights the complex nature of seasonal variation of faecal risk, and questions the assumption that risk is higher in the rainy season.

This paper explores the influence of perception on behaviours associated with emptying of faecal sludge from non-sewered sanitation systems using findings from a study on the emptying behaviour of residents of Khulna city, Bangladesh. The purpose of the study was to highlight perception as a behaviour determinants as well as develop perception management strategies for the design, plan and implementation of effective behaviour change intervention programmes with a focus on ‘scheduled emptying’. The study uses a mixed-method cross-sectional approach to collect data through structured household questionnaire surveys, face-to-face key informant interviews, group interviews, and structured observations. The study revealed that the emptying behaviour of the community was reactive, untimely and unsafe and over half of the systems had never been emptied, which was traced to emptying perceptions that encouraged a laissez-faire attitude within households and the community. The study concluded by proposing a perception management model to achieve behaviour change towards scheduled emptying via perception change.

The co-treatment of two synthetic faecal sludges (FS-1 and FS-2) with municipal synthetic wastewater (WW) was evaluated in an aerobic granular sludge (AGS) reactor. After characterisation, FS-1 showed the following concentrations, representative for medium-strength FS: 12,180 mg TSS L−1, 24,300 mg total COD L−1, 93.8 mg PO3-P L−1, and 325 mg NH4-N L−1. The NO3-N concentration was relatively high (300 mg L−1). For FS-2, the main difference with FS-1 was a lower nitrate concentration (18 mg L−1). The recipes were added consecutively, together with the WW, to an AGS reactor. In the case of FS-1, the system was fed with 7.2 kg total COD m−3d−1 and 0.5 kg Nitrogen m−3d−1. Undesired denitrification occurred during feeding and settling resulting in floating sludge and wash-out. In the case of FS-2, the system was fed with 8.0 kg total COD m−3d−1 and 0.3 kg Nitrogen m−3d−1. The lower NO3-N concentration in FS-2 resulted in less floating sludge, a more stabilised granular bed and better effluent concentrations. To enhance the hydrolysis of the slowly biodegradable particulates from the synthetic FS, an anaerobic stand-by period was added and the aeration period was increased. Overall, when compared to a control AGS reactor, a lower COD consumption (from 87 to 35 mg g−1 VSS h−1), P-uptake rates (from 6.0 to 2.0 mg P g VSS−1 h−1) and NH4-N removal (from 2.5 to 1.4 mg NH4-N g VSS−1 h−1) were registered after introducing the synthetic FS. Approximately 40% of the granular bed became flocculent at the end of the study, and a reduction of the granular size accompanied by higher solids accumulation in the reactor was observed. A considerable protozoa Vorticella spp. bloom attached to the granules and the accumulated particles occurred; potentially contributing to the removal of the suspended solids which were part of the FS recipe.