Browsing by Author "Cartmell, Elise"
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Item Open Access Advanced reactor technology for wastewater treatment.(Cranfield University, 2015-04) Hassard, Francis; Stephenson, Tom; Cartmell, EliseElevated stringency regarding discharges and an aging asset base represent challenges to modern wastewater treatment. This requires upgrade of existing wastewater assets for low energy nutrient removal for minimal cost. Advanced rotating biofilm reactors can be used as a pre-treatment, high organic loading rate (OLR), low hydraulic residence time (HRT) treatment facilitating upgrade of existing wastewater treatment plant (WWTP). The threshold for stable nitrification in rotating biological contactors (RBCs) was assumed to be 15 g.BOD₅.m⁻²d⁻¹ however media modifications have shown that this value can be elevated to ~35 g.sCOD.m⁻²d⁻¹ (73.5 g.BOD₅.m⁻²d⁻¹ ) in rotating biofilm reactors (RBR). Mesh media was compared to two different reticulated foam media, the mesh media had similar porosities but elevated performance compared to the foam media. Elevated OLR resulted in lower volumetric bacterial viability suggesting inhibition at >100 g.sCOD.m⁻²d⁻¹. Comparison of four different mesh media suggested that high porosity mesh media is best for performance and to prevent pore clogging. Bacterial specific activity increased with OLR, but performance at very high OLR decreased. Biofilm reactors can be operated in a ‘hybrid’ configuration where settled bacterial solids can be recycled into the biofilm reactor to improve performance by reducing the effective biofilm OLR. Studies at full scale revealed that extracellular enzyme activity was higher in biofilms compared to suspended growth bacteria. Hybrid upgrade of existing wastewater treatment works resulted in 52 and 40% increase in removal rate of COD and NH₄-N respectively. Comparing different solids type for hybrid reactors utilising activated sludge flocs had the greatest performance benefit compared to HS and FE respectively for sCOD and NH₄-N removal. Incorporating a solids feed in hybrid reactors improved nitrification and organics removal at lower loading. However the solids in the recycle feed reduced denitrification at very high OLR suggesting flocs inhibit denitrification. Hybrid RBRs have 4.8 fold increase in protein EEA compared to single pass reactors under similar conditions. Recycling bacterial solids reduces the effective OLR on the biofilm and confers significant performance benefits. Upfront RBRs provide suitable upgrade for existing WWTP.Item Open Access Anaerobic Digestion Foaming Causes(Cranfield University, 2008-10) Ganidi, Nafsika; Tyrrel, Sean; Cartmell, EliseAnaerobic digestion foaming has been encountered in several sewage treatment plants in the UK. Foaming has raised major concerns for the water utilities due to significant impacts on process efficiency and operational costs. Several foaming causes have been suggested over the past few years by researchers. However, the supporting experimental information is limited and in some cases site specific. The present report aimed to provide a better understanding of the anaerobic digestion foaming problem and to identify the underlying mechanisms of foaming. Field and laboratory investigation identified organic loading as a cause of foaming. Bench scale batch digestion studies in sludge showed that the critical organic loading for foaming was at 2.5 kg VS.m -3 while the 5 kg VS.m -3 resulted in persistent foaming. Moreover, full scale foaming digesters exhibited higher foaming potential in digested sludge under aeration in the laboratory than the full scale non- foaming digesters indicating that the concentration of surface active agents was higher. Further investigation of the effect of the surface active compounds, BSA and n-valeric acid on foaming showed that both compounds induced persistent foaming at all the examined concentrations. Filamentous bacteria contribution to foam initiation and stabilization was considered insignificant, apart from one occasion (FI:5), due to the abundance of filaments in foaming sludge (FI≤3) and their partitioning in foam (FI≤3). Part of the current work also assessed the cost implications of a foaming incident at the full scale. The antifoam cost was found to be of major concern for the water utilities costing between £1.30 and £13.00 per 1000 m 3 of digester volume per day. However, there was no information on biogas and energy loss whereas the information provided on cleaning, maintenance costs and manpower working hours was poor. Thus, the overall cost of a foaming incident at the full scale could not be estimated at this stage.Item Open Access Anaerobic digestion foaming causes – A review(Elsevier, 2009-12) Ganidi, Nafsika; Tyrrel, Sean F.; Cartmell, EliseAnaerobic digestion foaming has been encountered in several sewage treatment plants in the UK. Foaming has raised major concerns for the water companies due to significant impacts on process efficiency and operational costs. Several foaming causes have been identified over the past few years by researchers. However, the supporting experimental information is limited and in some cases absent. The present report aims to provide a detailed review of the current anaerobic digestion foaming problem and to identify gaps in knowledge regarding the theory of foam formation in anaerobic digesters.Item Open Access Assessing potential modifications to the activated sludge process to improve simultaneous removal of a diverse range of micropollutants(Elsevier Science B.V., Amsterdam., 2014-10-01T00:00:00Z) Petrie, Bruce; McAdam, Ewan J.; Lester, John N.; Cartmell, EliseIt is proposed that wastewater treatment facilities meet legislated discharge limits for a range of micropollutants. However, the heterogeneity of these micropollutants in wastewaters make removal difficult to predict since their chemistry is so diverse. In this study, a range of organic and inorganic micropollutants known to be preferentially removed via different mechanisms were selected to challenge the activated sludge process (ASP) and determine its potential to achieve simultaneous micropollutant removal. At a fixed hydraulic retention time (HRT) of 8 h, the influence of an increase in solids retention time (SRT) on removal was evaluated. Maximum achievable micropollutant removal was recorded for all chemicals (estrogens, nonylphenolics and metals) at the highest SRT studied (27 days). Also, optimisation of HRT by extension to 24 h further augmented organic biodegradation. Most notable was the enhancement in removal of the considerably recalcitrant synthetic estrogen 17a-ethinylestradiol which increased to 65 analysis indicates that this enhanced micropollutant behaviour is ostensibly related to the concomitant reduction in food: microorganism ratio. Interestingly, extended HRT also initiated nonylphenol biodegradation which has not been consistently observed previously in real wastewaters. However, extending HRT increased the solubilisation of particulate bound metals, increasing effluent aqueous metals concentrations (i.e., 0.45± 19%. Regressionmm filtered) by > compliance. Consequently, identification of an optimum process condition for generic micropollutant removal is expected to favour a more integrated approach where upstream process unit optimisation (i.e., primary sedimentation) is demanded to reduce loading of the particle bound metal phase onto the ASP, thereby enabling longer HRT in the ASP to be considered for optimum removal of organic micropollutants.100%. This is significant as only the aqueous metal phase is to be considered for environmentalItem Open Access Bacteriophages - potential for application in wastewater treatment processes.(Elsevier Science B.V., Amsterdam., 2005-03-01T00:00:00Z) Withey, S.; Cartmell, Elise; Avery, L. M.; Stephenson, TomBacteriophages are viruses that infect and lyse bacteria. Interest in the ability of phages to control bacterial populations has extended from medical applications into the fields of agriculture, aquaculture and the food industry. Here, the potential application of phage techniques in wastewater treatment systems to improve effluent and sludge emissions into the environment is discussed. Phage-mediated bacterial mortality has the potential to influence treatment performance by controlling the abundance of key functional groups. Phage treatments have the potential to control environmental wastewater process problems such as: foaming in activated sludge plants; sludge dewaterability and digestibility; pathogenic bacteria; and to reduce competition between nuisance bacteria and functionally important microbial populations. Successful application of phage therapy to wastewater treatment does though require a fuller understanding of wastewater microbial community dynamics and interactions. Strategies to counter host specificity and host cell resistance must also be developed, as should safety considerations regarding pathogen emergence through transduction.Item Open Access Bioconversion of carbon dioxide in anaerobic digesters for on-site carbon capture and biogas enhancement - A review(Taylor & Francis, 2017-12-11) Bajón Fernández, Yadira; Soares, Ana; Koch, K.; Vale, P.; Cartmell, EliseEnergy consumption of the water sector presents an increasing energy demand, contrary to GHG mitigation aims. As a result, research aimed at capturing emitted CO2 and at developing treatment technologies with a low energy demand and increased renewable energy production has increased, leading to a surge in implementation of anaerobic digestion (AD). Valorization of the biogenic CO2 emitted with biogas AD (estimated at over 1 MtCO2 per annum for the UK water and organic waste sectors), presents an opportunity to further reduce carbon footprint and support energy supply decarburization. This paper reviews bioconversion of CO2 into CH4 in ADs (without addition of H2) as a means to valorize CO2 emissions. The review has concluded this to be a promising solution to reduce carbon footprint and uplift renewable energy production. However, in order to increase readiness for implementation (1) the mechanisms of CO2 utilization need to be elucidated, including the sources of additional H2 needed, (2) studies need to report more thoroughly the conditions of CO2 injection and (3) trials where ADs are integrated with gas to liquid mass transfer technologies need to be performed.Item Open Access Biological carbon dioxide utilisation in food waste anaerobic digesters(Elsevier, 2015-06-09) Bajón Fernández, Yadira; Green, K.; Schuler, K.; Soares, Ana; Vale, P.; Alibardi, Luca; Cartmell, EliseCarbon dioxide (CO2) enrichment of anaerobic digesters (AD) was previously identified as a potential on-site carbon revalorisation strategy. This study addresses the lack of studies investigating this concept in up-scaled units and the need to understand the mechanisms of exogenous CO2 utilisation. Two pilot-scale ADs treating food waste were monitored for 225 days, with the test unit being periodically injected with CO2 using a bubble column. The test AD maintained a CH4 production rate of 0.56 ± 0.13 m3 CH4·(kg VSfed d)−1 and a CH4 concentration in biogas of 68% even when dissolved CO2 levels were increased by a 3 fold over the control unit. An additional uptake of 0.55 kg of exogenous CO2 was achieved in the test AD during the trial period. A 2.5 fold increase in hydrogen (H2) concentration was observed and attributed to CO2 dissolution and to an alteration of the acidogenesis and acetogenesis pathways. A hypothesis for conversion of exogenous CO2 has been proposed, which requires validation by microbial community analysis.Item Open Access Biosolids recycling impact on biofilm extracellular enzyme activity and performance of hybrid rotating biological reactors(Elsevier, 2019-11-30) Hassard, Francis; Biddle, Jeremy; Cartmell, Elise; Coulon, Frederic; Stephenson, TomBiological processes for wastewater treatment is limited by extracellular enzyme activity (EEA) of the biofilm on polymeric substrates. The efficiency of biodegradation / biosorption mechanisms causing EEA and organic load removal in biofilms remains unknown. Our hypothesis was that the limiting step of biological process can be overcome by biostimulation and/or bioaugmentation of the return sludge in hybrid biofilm reactors, which leads to competition between suspended and attached bacteria and lower effective substrate to microrganism ratio. Therefore, we considered more active biosolids to perform best at enhancing reactor removal rate. To test this, the efficacy of recycling distinct bio-solids types considered to have different bacterial activity such as final effluent (FE), humus solids (HS) and recycle activated sludge (RAS) on performance improvements of rotating biofilm reactors (RBRs). These bio-solids were investigated under high organic loading rates (OLR) and solids loading rates (SLR) using pilot scale reactors receiving real municipal wastewaters. Controlled overloading of RBRs revealed that EEA improved with increasing OLR/SLR. High SLR (>3.3 kg Total Suspended Solids m−2 d−1) delayed and decreased the reduction of organic and inorganic removal rates in the biological processes which commonly occurs under high OLRs. This effect was more pronounced in the highest activity solids (RAS > HS > FE) suggesting the activity and function of bio-solids was critical to improve performance of RBRs. High OLR and SLR induced efficient denitrification and organics removal within the biofilm reactor at residence times of <5 min. Recycling active solids permitted EEA despite overloading which was critical to the performance of the RBRs.Item Open Access Carbon capture and biogas enhancement by carbon dioxide enrichment of anaerobic digesters treating sewage sludge or food waste(Elsevier Science B.V., Amsterdam., 2014-05-01T00:00:00Z) Bajón Fernández, Yadira; Soares, Ana; Villa, Raffaella; Vale, P.; Cartmell, EliseThe increasing concentration of carbon dioxide (CO2) in the atmosphere and the stringent greenhouse gases (GHG) reduction targets, require the development of CO2 sequestration technologies applicable for the waste and wastewater sector. This study addressed the reduction of CO2 emissions and enhancement of biogas production associated with CO2 enrichment of anaerobic digesters (ADs). The benefits of CO2 enrichment were examined by injecting CO2 at 0, 0.3, 0.6 and 0.9M fractions into batch ADs treating food waste or sewage sludge. Daily specific methane (CH4) production increased 11-16% for food waste and 96-138% for sewage sludge over the first 24h. Potential CO2 reductions of 8-34% for sewage sludge and 3-11% for food waste were estimated. The capacity of ADs to utilise additional CO2 was demonstrated, which could provide a potential solution for onsite sequestration of CO2 streams while enhancing renewable energy production.Item Open Access Carbon dioxide utilisation in anaerobic digesters as an on-site carbon revalorisation strategy(Cranfield University, 2014-11) Bajón Fernández, Yadira; Cartmell, Elise; Soares, Ana; Vale, PeterThe increasing carbon footprint of the water and organic waste sectors has led to water utilities to voluntarily include carbon mitigation approaches within their strategic plans and to an increase in research aimed at mitigating carbon dioxide (CO2) emissions. Injection of CO2 in anaerobic digesters (ADs) for its bioconversion into methane (CH4) has been identified as a potential solution. However, previous literature provided limited knowledge of the carbon benefits obtainable and presented conflicting information regarding the mechanisms of CO2 utilisation. This thesis investigated the potential of injecting exogenous CO2 into ADs for its bioconversion into CH4 to reduce CO2 emissions from water and organic waste facilities. Batch laboratory scale and continuous pilot-scale ADs enriched with CO2 were operated. A substrate dependant response to exogenous CO2 was reported for the first time and potential CO2 savings of up to 34% and 11% were estimated for sewage sludge and food waste batch ADs, respectively, injected with CO2 before the digestion process. Higher benefits in CH4 production were observed in sewage sludge ADs than in food waste units. An up to 2.4 fold increase in CH4 production during the 24 hours following saturation with CO2 was obtained in sewage sludge units, while benefit was limited to 1.16 fold in food waste ADs. Microbial community analyses were performed to elucidate CO2 fate mechanisms. An increase of up to 80% in the activity of Methanosaetaceae (obligate acetoclastic methanogen) was observed in sewage sludge ADs periodically enriched with CO2. Methanosaetaceae was scarce (4.3±1.7%) in food waste units, which was attributed to an inhibitory concentration of ammonia (4 gL-1 NH4-N). Based on Archaea analyses and on monitoring hydrogen (H2) and volatile fatty acids (VFA) speciation dynamics in a pilot-scale AD, it was proposed that exogenous CO2 is reduced by homoacetogenesis (Wood-Ljungdahl mechanism) and the acetate generated by this route is converted to CH4 by acetoclastic methanogenesis. Gas to liquid mass transfer was identified as limiting of the amount of dissolved CO2 loaded to an AD and the complex rheology of anaerobically digested media as detrimental for transfer performance. An increase of apparent viscosity (μa) from 130 to 340 cPo (typical variability of sewage sludge) reduced gas transfer efficiency (GTE) by 6 percentage points. The use of bubble columns was identified as suitable for further scaled-up units. Injection of CO2 could be performed in the digestate recirculation loop of single phase ADs or in the first phase of two phase ADs (TPADs), with CO2 sourced from off-gas of biogas upgrading technologies. It has been demonstrated that bioconversion of CO2 in ADs can reduce carbon footprint and increase CH4 production, with the possibility of becoming an on-site carbon revalorisation strategy.Item Open Access Characterisation and control of the biosolids storage environment: Implications for E. coli dynamics(Elsevier, 2020-08-15) Fane, Sarah Elizabeth; Nocker, Andreas; Vale, Peter; Rivas Casado, Monica; Cartmell, Elise; Harris, Jim A.; Bajón Fernández, Yadira; Tyrrel, Sean F.E. coli survival in biosolids storage may present a risk of non-compliance with guidelines designed to ensure a quality product safe for agricultural use. The storage environment may affect E. coli survival but presently, storage characteristics are not well profiled. Typically biosolids storage environments are not actively controlled or monitored to support increased product quality or improved microbial compliance. This two-phased study aimed to identify the environmental factors that control bacterial concentrations through a long term, controlled monitoring study (phase 1) and a field-scale demonstration trial modifying precursors to bacterial growth (phase 2). Digested and dewatered biosolids were stored in operational-scale stockpiles to elucidate factors controlling E. coli dynamics. E. coli concentrations, stockpile dry solids, temperature, redox and ambient weather data were monitored. Results from ANCOVA analysis showed statistically significant (p < 0.05) E. coli reductions across storage periods with greater die-off in summer months. Stockpile temperature had a statistically significant effect on E. coli survival. A 4.5 Log reduction was measured in summer (maximum temperature 31 °C). In the phase 2 modification trials, covered stockpiles were able to maintain a temperature >25 °C for a 28 day period and achieved a 3.7 Log E. coli reduction. In winter months E. coli suppression was limited with concentrations >6 Log10 CFU g−1 DS maintained. The ANCOVA analysis has identified the significant role that physical environmental factors, such as stockpile temperature, has on E. coli dynamics and the opportunities for controlItem Open Access The characterization of feces and urine: a review of the literature to inform advanced treatment technology(Taylor and Francis, 2015-02-25) Rose, C.; Parker, Alison; Jefferson, Bruce; Cartmell, EliseThe safe disposal of human excreta is of paramount importance for the health and welfare of populations living in low income countries as well as the prevention of pollution to the surrounding environment. On-site sanitation (OSS) systems are the most numerous means of treating excreta in low income countries, these facilities aim at treating human waste at source and can provide a hygienic and affordable method of waste disposal. However, current OSS systems need improvement and require further research and development. Development of OSS facilities that treat excreta at, or close to, its source require knowledge of the waste stream entering the system. Data regarding the generation rate and the chemical and physical composition of fresh feces and urine was collected from the medical literature as well as the treatability sector. The data were summarized and statistical analysis was used to quantify the major factors that were a significant cause of variability. The impact of this data on biological processes, thermal processes, physical separators, and chemical processes was then assessed. Results showed that the median fecal wet mass production was 128 g/cap/day, with a median dry mass of 29 g/cap/day. Fecal output in healthy individuals was 1.20 defecations per 24 hr period and the main factor affecting fecal mass was the fiber intake of the population. Fecal wet mass values were increased by a factor of 2 in low income countries (high fiber intakes) in comparison to values found in high income countries (low fiber intakes). Feces had a median pH of 6.64 and were composed of 74.6% water. Bacterial biomass is the major component (25–54% of dry solids) of the organic fraction of the feces. Undigested carbohydrate, fiber, protein, and fat comprise the remainder and the amounts depend on diet and diarrhea prevalence in the population. The inorganic component of the feces is primarily undigested dietary elements that also depend on dietary supply. Median urine generation rates were 1.42 L/cap/day with a dry solids content of 59 g/cap/day. Variation in the volume and composition of urine is caused by differences in physical exertion, environmental conditions, as well as water, salt, and high protein intakes. Urine has a pH 6.2 and contains the largest fractions of nitrogen, phosphorus, and potassium released from the body. The urinary excretion of nitrogen was significant (10.98 g/cap/day) with urea the most predominant constituent making up over 50% of total organic solids. The dietary intake of food and fluid is the major cause of variation in both the fecal and urine composition and these variables should always be considered if the generation rate, physical, and chemical composition of feces and urine is to be accurately predicted.Item Open Access Coagulation–flocculation process with metal salts, synthetic polymers and biopolymers for the removal of trace metals (Cu, Pb, Ni, Zn) from municipal wastewater(Springer, 2018-07-02) Hargreaves, Andrew J.; Vale, Peter; Whelan, Jonathan; Alibardi, Luca; Constantino, Carlos; Dotro, Gabriela; Cartmell, EliseTo ensure compliance with regulatory standards, it is important to examine the potential of treatment technologies to enhance trace metal removal from wastewater. This study investigated the effectiveness of coagulation–flocculation at removing trace metals from humus effluent with ferric chloride (FeCl3), the synthetic polymer polyethyleneimine (PEI) and the biopolymers chitosan and floculan. Effluent samples were collected from a trickling filter treatment works operating in the UK and contained 21 ± 4 μg/L Cu, 0.8 ± 0.1 μg/L Pb, 4 ± 1 μg/L Ni and 43 ± 9 μg/L Zn. The influence of coagulant dosage and the velocity and time of the slow mixing stage were studied via a series of jar tests. Chitosan and PEI had a moderate effect on the removal of trace metals (≤ 35%). FeCl3 removed 48% Cu, 56% Pb and 41% Zn at the optimised dose of 0.10 mg/L. At the optimised dose of 0.25 mg/L, floculan removed 77% Cu, 68% Pb and 42% Zn. The dominant mechanism for particle removal by FeCl3 was enmeshment in the precipitates (i.e. sweep flocculation), whereas, for floculan, inter-particle bridging was the dominant removal mechanism. Overall, FeCl3 and floculan were found to be most effective at removing trace metals from wastewater.Item Open Access Comparing flow cytometry with culture-based methods for microbial monitoring and as a diagnostic tool for assessing drinking water treatment processes(Elsevier, 2019-06-18) Cheswick, Ryan Ashley; Cartmell, Elise; Lee, Susan; Upton, Andrew; Weir, Paul; Moore, Graeme; Nocker, Andreas; Jefferson, Bruce; Jarvis, PeterFlow cytometry (FCM) and the ability to measure both total and intact cell populations through DNA staining methodologies has rapidly gained attention and consideration across the water sector in the past decade. In this study, water quality monitoring was undertaken over three years across 213 drinking water treatment works (WTW) in the Scottish Water region (Total n = 39,340). Samples subject to routine regulatory microbial analysis using culture-based methods were also analysed using FCM. In addition to final treated water, the bacterial content in raw water was measured over a one-year period. Three WTW were studied in further detail using on-site inter-stage sampling and analysis with FCM. It was demonstrated that there was no clear link between FCM data and the coliform samples taken for regulatory monitoring. The disinfectant Ct value (Ct = mg·min/L) was the driving factor in determining final water cell viability and the proportion of intact cells (intact/total cells) and the frequency of coliform detections in the water leaving the WTW. However, the free chlorine residual, without consideration of treatment time, was shown to have little impact on coliform detections or cell counts. Amongst the three treatment trains monitored in detail, the membrane filtration WTW showed the greatest log removal and robustness in terms of final water intact cell counts. Flow cytometry was shown to provide insights into the bacteriological quality of water that adds significant value over and above that provided by traditional bacterial monitoring.Item Open Access Comparison between disintegrated and fermented sewage sludge for production of a carbon source suitable for biological nutrient removal(Elsevier Science B.V., Amsterdam., 2010-03-15T00:00:00Z) Soares, Ana; Kampas, Pantelis; Maillard, Sarah; Wood, Elizabeth; Brigg, Jon; Tillotson, Martin; Parsons, Simon A.; Cartmell, EliseThere is a need to investigate processes that enable sludge re-use while enhancing sewage treatment efficiency. Mechanically disintegrated thickened surplus activated sludge (SAS) and fermented primary sludge were compared for their capacity to produce a carbon source suitable for BNR by completing nutrient removal predictive tests. Mechanically disintegration of SAS using a deflaker enhanced volatile fatty acids (VFAs) content from 92 to 374 mg l−1 (4.1-fold increase). In comparison, primary sludge fermentation increased the VFAs content from 3.5 g l−1 to a final concentration of 8.7 g l−1 (2.5-fold increase). The carbon source obtained from disintegration and fermentation treatments improved phosphate (PO4-P) release and denitrification by up to 0.04 mg NO3-N g−1 VSS min−1 and 0.031 mg PO4-P g−1 VSS min−1, respectively, in comparison to acetate (0.023 mg NO3-N g−1 VSS min−1and 0.010 mg PO4-P g−1 VSS min−1). Overall, both types of sludge were suitable for BNR but disintegrated SAS displayed lower carbon to nutrient ratios of 8 for SCOD:PO4-P and 9 for SCOD:NO3-N. On the other hand, SAS increased the concentration of PO4-P in the settled sewage by a further 0.97 g PO4-P kg−1 SCOD indicating its potential negative impact towards nutrient recycItem Open Access Conceptual energy and water recovery system for self-sustained nano membrane toilet(Energy Conservation and Management, 2016-08-12) Hanak, Dawid P.; Kolios, Athanasios; Onabanjo, Tosin; Wagland, Stuart Thomas; Patchigolla, Kumar; Fidalgo Fernandez, Beatriz; Manovic, Vasilije; McAdam, Ewan J.; Parker, Alison; Williams, Leon; Tyrrell, Sean; Cartmell, EliseWith about 2.4 billion people worldwide without access to improved sanitation facilities, there is a strong incentive for development of novel sanitation systems to improve the quality of life and reduce mortality. The Nano Membrane Toilet is expected to provide a unique household-scale system that would produce electricity and recover water from human excrement and urine. This study was undertaken to evaluate the performance of the conceptual energy and water recovery system for the Nano Membrane Toilet designed for a household of ten people and to assess its self-sustainability. A process model of the entire system, including the thermochemical conversion island, a Stirling engine and a water recovery system was developed in Aspen Plus®. The energy and water recovery system for the Nano Membrane Toilet was characterised with the specific net power output of 23.1 Wh/kgsettledsolids and water recovery rate of 13.4 dm3/day in the nominal operating mode. Additionally, if no supernatant was processed, the specific net power output was increased to 69.2 Wh/kgsettledsolids. Such household-scale system would deliver the net power output (1.9–5.8 W). This was found to be enough to charge mobile phones or power clock radios, or provide light for the household using low-voltage LED bulbs.Item Open Access Developing a nutrient recovery process for recovering nutrients in anaerobic digestate in low income countries(Cranfield University, 2015-06) Rose, Christopher; Parker, Alison; Cartmell, EliseIt is estimated that 2.7 billion people worldwide are served by on-site sanitation facilities that require faecal sludge management. Anaerobic digestion is a treatment mechanism that can provide faecal sludge management, methane production and an effluent digestate rich in nutrients. However, there is a paucity of information regarding the composition of the input faecal sludge which hinders the advancement of anaerobic digestion treatment and downstream nutrient recovery together with a lack of knowledge as to how best to recover these output nutrients in a simple process. Following an initial review to collate composition data for fresh faeces and urine, practical studies examined the physical, biological and chemical composition and variation of four different types of faecal sludge from on-site sanitation facilities. Faecal sludge storage strongly influenced the biodegradability and methane production potential in subsequent anaerobic digestion. However, the high concentrations of ammonium observed in faecal sludge (520-1853 mg NH4-N L- 1 ) were highlighted as a key goal for nutrient recovery and the ability of biochar and clinoptilolite as natural adsorbents for ammonium recovery in a drying bed application were investigated through batch and dynamic studies using synthetic and real digestate. Batch tests observed ammonium uptake of 5 and 12.2 mg NH4-N/g for biochar and clinoptilolite respectively whilst under dynamic experimental conditions the most efficient operation for ammonium recovery was at the longest empty bed contact times (354 minutes), ensuring the maximum fertiliser value was obtained (60g NH4-N/kg clinoptilolite). Nevertheless, clogging occurred rapidly at the surface of the media bed (0.04 – 0.5 kg TS/m2 ), consequently a sacrificial sand layer (0.05 m) was included to increase the longevity of the nutrient recovery system (15 fold increase in TS application rates). It has been demonstrated that clinoptilolite can effectively be used as part of a sludge drying bed configuration to recover nutrients from digestate and the saturated media can be used directly as a fertiliser product or blended with the dried sludge to create a balanced nitrogen, phosphorus and potassium fertiliser product (5.9% NH4-N/ 4.2% P/ ≥6.0% K+ ).Item Open Access Development of a staged anaerobic pond for methane recovery from domestic wastewater(Elsevier, 2018-08-08) Cruddas, Peter; McAdam, Ewan; Asproulis, Nikolaos; Antoniadis, Antonis F.; Ansari, Irfan; Best, D.; Jefferson, Bruce; Cartmell, Elise; Collins, G.; Porca, E.; Peña-Varón, M. R.Since their inception in larger pond systems, the focus of anaerobic ponds has shifted from solids removal to optimising biogas production and reducing physical footprint to minimise land requirements. In this study, a horizontally baffled (HBAP) and vertically baffled (VBAP) anaerobic pond were compared. Distinct differences in the removal efficiency of COD fractions were observed, with particulate COD removal of 78% and 32%, and soluble COD removal of −26% and 19% in the HBAP and VBAP, respectively. A staged pond (SAP) was constructed through an HBAP placed upstream of a VBAP, with an additional HBAP used as a control (CAP). The SAP demonstrated superior biogas recovery potential over the control: methane production by the conclusion of the study was 6.09 and 9.04 LCH4 m−3 wastewater treated for the CAP and SAP, respectively. Methanogenic activity in the ponds was higher closer to the outlet, and hydrogenotrophic methanogenesis dominated over acetoclastic pathways.Item Open Access Diagnosis of an anaerobic pond treating temperate domestic wastewater: An alternative sludge strategy for small works(Elsevier, 2014-01-15) Cruddas, Peter; Wang, K.; Best, D.; Jefferson, Bruce; Cartmell, Elise; Parker, Alison; McAdam, Ewan J.An anaerobic pond (AP) for treatment of temperate domestic wastewater has been studied as a small works sludge management strategy to challenge existing practice which comprises solids separation followed by open sludge storage, for up to 90 days. During the study, effluent temperature ranged between 0.1 °C and 21.1 °C. Soluble COD production was noted in the AP at effluent temperatures typically greater than 10 °C and was coincident with an increase in effluent volatile fatty acids (VFA) concentration, which is indicative of anaerobic degradation. Analysis from ports sited along the AP's length, demonstrated VFA to be primarily formed nearest the inlet where most solids deposition initially incurred, and confirmed the anaerobic reduction of sludge within this chamber. Importantly, the sludge accumulation rate was 0.06 m3 capita−1 y−1 which is in the range of APs operated at higher temperatures and suggests a de-sludge interval of 2.3–3.8 years, up to 10 times longer than current practice for small works. Coincident with the solids deposition profile, biogas production was predominantly noted in the initial AP section, though biogas production increased further along the AP's length following start-up. A statistically significant increase in mean biogas production of greater than an order of magnitude was measured between winters (t(n=19) = 5.52, P < 0.001) demonstrating continued acclimation. The maximum methane yield recorded was 2630 mgCH4 PE−1 d−1, approximately fifty times greater than estimated from sludge storage (57 mgCH4 PE−1 d−1). Anaerobic ponds at small works can therefore enable sludge reduction and longer sludge holding times than present thus offsetting tanker demand whilst reducing fugitive methane emissions currently associated with sludge storage, and based on the enhanced yield noted, could provide a viable opportunity for local energy generation.Item Open Access Disruption of cells in biosolids affects E. coli dynamics in storage(IWA Publishing, 2019-05-22) Fane, Sarah Elizabeth; Madureira, D.; Nocker, A.; Vale, P.; Rivas Casado, Monica; Wilson, A.; Bajón Fernández, Yadira; Harris, Jim A.; Cartmell, Elise; Tyrrel, SeanAchieving microbial compliance during biosolids storage can be complicated by the unpredictable increase of Escherichia coli. Thermal treatment during anaerobic digestion (AD) and the effects of dewatering may be a significant factor contributing to indicator survival. Shear forces present during dewatering may promote cell damage, releasing nutrient for E. coli growth. The effect of cell damage on E. coli survival was assessed in laboratory-scale thermal and physical disruption experiments. E. coli growth curves for disrupted treatments were compared with control conditions and quantified using flow cytometry and membrane filtration techniques. A significant difference (p < 0.05) in the level of damaged cells between control and disrupted conditions was observed. For thermal and physical disruption treatments, the peak of E. coli concentration increased significantly by 1.8 Log and 2.4 Log (CFU (colony forming units) g−1 DS), respectively, compared with control treatments. Research findings contribute to the understanding of bacterial growth and death dynamics in biosolids
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