The impact of hydraulic retention time on the performance of two configurations of anaerobic pond for municipal sewage treatment

Anaerobic ponds have the potential to contribute to low carbon wastewater treatment, however are currently restricted by long hydraulic residence time (HRT) which leads to large land requirements. A two-stage anaerobic pond (SAP) design was trialled against a single-stage control (CAP) over four HRTs down to 0.5 days, to determine the lowest HRT at which the ponds could operate effectively. No statistical differences were observed in particulate removal between the ponds over all four HRTs, suggesting solids loading is not a critical factor in AP design. Significantly higher biogas production rates were observed in the SAP than the CAP at 1.5 d and 1.0 d HRT, and microbial community profiling suggests the two-stage design may be facilitating spatial separation of the anaerobic digestion process along reactor length. Hydrogenotrophic methanogensis dominated over aceticlastic, with acetate oxidisation a likely degradation pathway. Experimental tracer studies were compared to CFD simulations, with the SAP showing greater hydraulic efficiency, and differences more pronounced at shorter HRTs. Greater flow recirculation between baffles was observed in CFD velocity profiles, demonstrating baffles can dissipate preferential flow patterns and increase effective pond volume, especially at high flow rates. The study demonstrates the potential of APs to be operated at shorter HRTs in psychrophilic conditions, presenting an opportunity for use as pre-treatments (in place of septic tanks) and primary treatment for full wastewater flows. Two-stage designs should be investigated to separate the stages of the anaerobic digestion process by creating preferential conditions along the pond length

The impact of hydraulic retention time on the performance of two configurations of anaerobic pond for municipal sewage treatment

Anaerobic ponds have the potential to contribute to low carbon wastewater treatment, however are currently restricted by long hydraulic residence time (HRT) which leads to large land requirements. A two-stage anaerobic pond (SAP) design was trialled against a single-stage control (CAP) over four HRTs down to 0.5 days, to determine the lowest HRT at which the ponds could operate effectively. No statistical differences were observed in particulate removal between the ponds over all four HRTs, suggesting solids loading is not a critical factor in AP design. Significantly higher biogas production rates were observed in the SAP than the CAP at 1.5 d and 1.0 d HRT, and microbial community profiling suggests the two-stage design may be facilitating spatial separation of the anaerobic digestion process along reactor length. Hydrogenotrophic methanogensis dominated over aceticlastic, with acetate oxidisation a likely degradation pathway. Experimental tracer studies were compared to CFD simulations, with the SAP showing greater hydraulic efficiency, and differences more pronounced at shorter HRTs. Greater flow recirculation between baffles was observed in CFD velocity profiles, demonstrating baffles can dissipate preferential flow patterns and increase effective pond volume, especially at high flow rates. The study demonstrates the potential of APs to be operated at shorter HRTs in psychrophilic conditions, presenting an opportunity for use as pre-treatments (in place of septic tanks) and primary treatment for full wastewater flows. Two-stage designs should be investigated to separate the stages of the anaerobic digestion process by creating preferential conditions along the pond length

Development of a staged anaerobic pond for methane recovery from domestic wastewater

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

Membrane distillation of concentrated blackwater: effect of temperature, solids concentration and membrane pore size

This study has elucidated the mechanisms governing water recovery from blackwater using membrane distillation, and has clarified the role of the organic particle fraction on membrane performance. Whilst fecal pathogen growth was initially observed at lower temperatures, pathogen inactivation was demonstrated over time, due to urea hydrolysis which liberated ammonia in excess of its toxic threshold. During the growth phase, membrane pore size <0.45 µm was sufficient to achieve high log reduction values for Escherichia coli, due to size exclusion complimented by the liquid–vapor interface which enhances selective transport for water. Higher feed temperatures benefitted rejection by promoting thermal inactivation and suppressing urea hydrolysis. Whilst the mechanism is not yet clear, suppression of hydrolysis reduced bicarbonate formation kinetics stabilizing the ammonia‐ammonium equilibrium which improved ammonium rejection. Blackwater particle concentration was studied by increasing fecal content. Particle fouling improved selectivity for coarse pore membranes but increased mass transfer resistance which reduced flux. Particle fouling induced wetting as noted by an eventual breakthrough of feed into the permeate. We propose that by incorporating upstream solid–liquid separation for particle separation to limit wetting and mass transfer resistance, membrane distillation can be a reliable solution for the recovery of high‐quality permeate from blackwater

The socialist blues? Citizenship, class and civil society

This article seeks to explore the relationship between the British labour movement, the Left and the Labour party. It does so through the intellectual prism of debates around citizenship and civil society. In this respect, I seek to recover a critical politics around questions of class from the New Left who were always critical of more mainstream ideas of citizenship. However, I also point to the limitations of those who have argued that meaningful forms of citizenship can no longer be connected to political parties and only occurs outside of state organizations. Political parties continue to need intellectual narratives to legitimate their role in society and to connect with the broader civil order.The Labour Party in this respect has seemingly broken with ‘New Labour’ and is searching for a new narrative. The rise of an intellectual grouping around ‘Blue Labour’ has made considerable headway recently and I seek to take a critical view of some of their ideas and ethical frameworks. Here I argue that changing class formations and a more pluralistic society potentially ask difficult questions of those who seek to revive the labour movement in troubled times

Postsecular planning? The idea of municipal spirituality

© 2015 Taylor & Francis. In the contemporary political context, religion is rarely out of the news, usually postulated as a regressive force, battling against modern liberal Western values. However, in everyday life, and specifically with regard to place value, the situation is more complex. This paper addresses the challenge this context and the attendant notion of postsecularism bring to planning practice. It argues that religious and spiritual values can be rearticulated as concepts which add a substantive positive dimension to planning and its conceptualisation and constructions of place. This is done by developing the notion of municipal spirituality, which draws on the theological conceptions of transcendence and the common good to redefine the value of places whose worth cannot easily be made in instrumental terms. In so doing, it challenges the current antagonistic opposition of religious and liberal democratic values, repositioning religious and spiritual concepts in an inclusive way. The idea of municipal spirituality illustrates how planning could have a role in defending and promoting such places. Further, it demonstrates the importance of engaging in agonistic rather than antagonistic debate, rearticulating the criteria on which places can be valued by planning practice

Irbesartan in Marfan syndrome (AIMS): a double-blind, placebo-controlled randomised trial

BACKGROUND: Irbesartan, a long acting selective angiotensin-1 receptor inhibitor, in Marfan syndrome might reduce aortic dilatation, which is associated with dissection and rupture. We aimed to determine the effects of irbesartan on the rate of aortic dilatation in children and adults with Marfan syndrome. METHODS: We did a placebo-controlled, double-blind randomised trial at 22 centres in the UK. Individuals aged 6-40 years with clinically confirmed Marfan syndrome were eligible for inclusion. Study participants were all given 75 mg open label irbesartan once daily, then randomly assigned to 150 mg of irbesartan (increased to 300 mg as tolerated) or matching placebo. Aortic diameter was measured by echocardiography at baseline and then annually. All images were analysed by a core laboratory blinded to treatment allocation. The primary endpoint was the rate of aortic root dilatation. This trial is registered with ISRCTN, number ISRCTN90011794. FINDINGS: Between March 14, 2012, and May 1, 2015, 192 participants were recruited and randomly assigned to irbesartan (n=104) or placebo (n=88), and all were followed for up to 5 years. Median age at recruitment was 18 years (IQR 12-28), 99 (52%) were female, mean blood pressure was 110/65 mm Hg (SDs 16 and 12), and 108 (56%) were taking β blockers. Mean baseline aortic root diameter was 34·4 mm in the irbesartan group (SD 5·8) and placebo group (5·5). The mean rate of aortic root dilatation was 0·53 mm per year (95% CI 0·39 to 0·67) in the irbesartan group compared with 0·74 mm per year (0·60 to 0·89) in the placebo group, with a difference in means of -0·22 mm per year (-0·41 to -0·02, p=0·030). The rate of change in aortic Z score was also reduced by irbesartan (difference in means -0·10 per year, 95% CI -0·19 to -0·01, p=0·035). Irbesartan was well tolerated with no observed differences in rates of serious adverse events. INTERPRETATION: Irbesartan is associated with a reduction in the rate of aortic dilatation in children and young adults with Marfan syndrome and could reduce the incidence of aortic complications

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

(Re) Locating community in relationships: questions for public policy

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.This paper argues that we should think of community as being about social relationships rather than a ‘thing’ that is ‘lost’, ‘found’ or ‘made’. The paper draws on the philosophy of Roberto Esposito and the sociology of David Studdert to highlight the overlaps in their approaches to community. Both argue that community is ontological, as unavoidably ‘with us’. The paper then draws upon two empirical examples to argue that this approach could enable a different kind of public policy in relation to community. Policy would focus on existing relationships as the starting point for any efforts to effect social change. The implications for contemporary debates about localism are explored at the end of the paper.I am very grateful to David Studdert and Valerie Walkerdine for inviting me to the workshop on community and localism held at Cardiff University in April 2014 that stimulated this special issue of Sociological Review. I am also very grateful to the Leverhulme Trust for the research funding and to Nick Coke, Tessy Britton and Laura Billings for their invaluable contributions to the arguments made. The comments from three referees, the editors and Patrick Devine-Wright were extremely helpful in improving the paper

Liberal conservatism, ‘boardization’ and the government of civil servants

Drawing inspiration from the loosely coupled genre of studies of governmentality, this article explores the emergence in Britain during the early years of the millennium of a distinctive liberal conservative scheme for the government of civil servants. The term ‘boardization’ has been used to characterize the trend to reproduce the technology of the board of directors in central government. Conservatives currently assign a distinctive role to the work of departmental ‘boards’ in the effective management of the Civil Service. Intimating the costs and risks of the Conservatives’ programme, we explore the role of diverse governmental forces in the emergence of the boards of the Civil Service as an object for action and intervention during the early years of the new millennium. We explore a mutation in the application of practices and techniques drawn from the domain of the business enterprise to the organization of the Civil Service. </jats:p