Browsing by Author "Cruddas, Peter"
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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 Selection of screw characteristics and operational boundary conditions to facilitate post-flush urine and faeces separation within single household sanitation systems(Royal Society of Chemistry, 2016-09-15) Mercer, Edwina; Cruddas, Peter; Williams, Leon; Kolios, Athanasios; Parker, Alison; Tyrrel, Sean; Cartmell, Elise; Pidou, Marc; McAdam, Ewan J.To ensure adequate access to sanitation in developing economies, off-grid single household sanitation has been proposed which obviates the need for significant infrastructure capital investment. Whilst treatment at this scale is most efficient when coupled to source separation (i.e. urine from faeces), existing source separation solutions have proved difficult to implement in this context. In this study, screw extrusion is therefore investigated to provide ‘post-flush’ source separation. Both screw characteristics and operational boundary conditions were evaluated. Preferential screw characteristics included tapering of the shaft and progressive pitch reduction, linked to a small extrusion aperture, the combination of which enhanced solids extrusion efficiency and promoted higher solids concentration in the extruded fraction. Whilst maximum extrusion efficiency was observed at high rotational speeds (over 400 rpm), this also promoted free water transport. Operating below 300 rpm instead introduced selectivity for transport of faecal sludge over urine, enabling phase separation. Constraining the volumetric ratio of urine to faeces also enhanced the extrusion rate of faecal sludge by increasing feed viscosity sufficient to overcome backpressure imposed by unmasticated food particles that would otherwise restrict separation. Importantly, this study demonstrates the feasibility of screw extrusion for ‘post flush’ separation of urine and faeces which constitutes a significant advancement towards realising sanitation at a single household scale.Item Open Access Tank costs for domestic rainwater harvesting in East Africa(Thomas Telford, 2012-12-31T00:00:00Z) Parker, Alison; Cruddas, Peter; Rowe, Nick; Carter, Richard; Webster, JamesRainwater harvesting from hard roofing can provide safe water to meet the basic domestic needs of several hundred million people in low-income countries. However, rainwater harvesting has a higher household cost than other low-technology water supplies such as protected springs. The storage tank is the most expensive part of the infrastructure required for rainwater harvesting: reducing this cost will enable rainwater harvesting to become a viable water source for many more households in low-income countries. This paper assesses the overall costs and different cost components of rainwater storage tanks. Costs are compared across a selection of tanks prefabricated in factories in Uganda, Kenya and the UK and constructed in situ in Uganda. Constructed tanks were always found to be cheaper than prefabricated ones. Tank size was an important factor, and it was found that tank cost per litre decreases as size increases. For all tank types, materials were the greatest cost.