Coagulant recovery from water treatment residuals: a review of applicable technologies

Conventional water treatment consumes large quantities of coagulant and produces even greater volumes of sludge. Coagulant recovery (CR) presents an opportunity to reduce both the sludge quantities and the costs they incur, by regenerating and purifying coagulant before reuse. Recovery and purification must satisfy stringent potable regulations for harmful contaminants, while remaining competitive with commercial coagulants. These challenges have restricted uptake and lead research towards lower-gain, lower-risk alternatives. This review documents the context in which CR must be considered, before comparing the relative efficacies and bottlenecks of potential technologies, expediting identification of the major knowledge gaps and future research requirements

The biotech developmental state? : investigating the Chinese gene revolution

China’s experience with agricultural biotechnology has been dramatic. Many new technologies have been developed by public sector research institutes that rival the outputs of the major biotech corporations. This has happened in the context of policy processes and priority setting exercises that are articulated in terms of the provision of public goods. In many respects this model contrasts with other parts of the world where the private sector has been dominant. The paper looks at how and why China has so vigorously pursued this biotech path, looking in particular at the role of science-policy networks in promoting a biotechnology discourse. It also looks at the particular challenges associated with developing a domestic biotech industry while managing multinationals such as Monsanto. A central question is to what extent this experience is an example of the state acting “developmentally”: steering both the private and public sectors to deliver public goods, and seizing the opportunities presented by a new technology while attempting to ensure that there is some level of social control over it. The paper asks: to what extent is China a biotech developmental state; and what are some of the challenges and limitations associated with this way of looking at the Chinese experience

Regulating biotechnology in China : the politics of biosafety

This paper looks at the politics of biosafety regulation in China. Policy processes around GM crops – Do we want them? What might they offer? What risks are associated with them? – take different shapes in different settings. In China biosafety decision-making is one key arena where agricultural biotechnology policy is defended and contested. Scientific disputes over who should practise risk assessment, and bureaucratic contests over who should have responsibility for regulation have simmered away, and reflect different perspectives on the role of agricultural biotechnology in Chinese agricultural and food systems. The paper looks at how risk assessments of Bt cotton and regulatory decisions about imports of GM soyabeans have used scientific arguments strategically to defend China’s nascent biotech industry and the country’s room for manoeuvre in relation to agricultural trade and food security policy choices. Chinese regulators talk the language of sound-science but in practice often use science flexibly. There are, however, dilemmas with this, and this is illustrated by the attempts of those scientifically or bureaucratically marginalised within the regulatory process to push for more wide-ranging consideration of the environmental impacts of insect-resistant cotton or potential commercialisations of GM food crops. These deliberations bring questions of uncertainty, precaution and the social nature of risk centre stage. Such an analysis of regulation shows that science-policy cultures are not only central to the politics of GM crops, they also open up far wider questions about how China negotiates the unchartered waters of constructing appropriate institutions to effectively manage the risks associated with the new technologies it is so rapidly embracing in its pursuit of modernisation and economic growth

Acidified and ultrafiltered recovered coagulants from water treatment works sludge for removal of phosphorus from wastewater

This study used a range of treated water treatment works sludge options for the removal of phosphorus (P) from primary wastewater. These options included the application of ultrafiltration for recovery of the coagulant from the sludge. The treatment performance and whole life cost (WLC) of the various recovered coagulant (RC) configurations have been considered in relation to fresh ferric sulphate (FFS). Pre-treatment of the sludge with acid followed by removal of organic and particulate contaminants using a 2kD ultrafiltration membrane resulted in a reusable coagulant that closely matched the performance FFS. Unacidified RC showed 53% of the phosphorus removal efficiency of FFS, at a dose of 20 mg/L as Fe and a contact time of 90 min. A longer contact time of 8 h improved performance to 85% of FFS. P removal at the shorter contact time improved to 88% relative to FFS by pre-acidifying the sludge to pH 2, using an acid molar ratio of 5.2:1 mol H+:Fe. Analysis of the removal of P showed that rapid phosphate precipitation accounted for >65% of removal with FFS. However, for the acidified RC a slower adsorption mechanism dominated; this was accelerated at a lower pH. A cost-benefit analysis showed that relative to dosing FFS and disposing waterworks sludge to land, the 20 year WLC was halved by transporting acidified or unacidified sludge up to 80 km for reuse in wastewater treatment. A maximum inter-site distance was determined to be 240 km above the current disposal route at current prices. Further savings could be made if longer contact times were available to allow greater P removal with unacidified RC

Reuse of recovered coagulants in water treatment: An investigation on the effect coagulant purity has on treatment performance

Coagulant recovery offers many potential benefits to water treatment, by reducing chemical demand and waste production. The key obstacle to successful implementation is achieving the same levels of treatment quality and process economics as commercial coagulants. This study has evaluated the selectivity of pressure-filtration in the role of a low-cost coagulant recovery technology from waterworks sludge. The treatment performance of the purified recovered coagulant was directly compared to fresh and raw recovered coagulants. DOC and turbidity removal by recovered coagulants was close to that of commercial coagulants, indicating that coagulant can be successfully recovered and regenerated by acidifying waterworks sludge. However, performance was less consistent, with a much narrower optimum charge neutralisation window and 10–30% worse removal performance under optimum conditions. This inferior performance was particularly evident for recovered ferric coagulants. The impact of this was confirmed by measuring THM formation potential and residual metals concentrations, showing 30–300% higher THMFPs when recovered coagulants were used. This study confirms that pressure-filtration can be operated on an economically viable basis, in terms of mass flux and fouling. However, the selectivity currently falls short of the purity required for potable treatment, due to incomplete rejection of sludge contaminants

Coagulant recovery and reuse for drinking water treatment

Coagulant recovery and reuse from waterworks sludge has the potential to significantly reduce waste disposal and chemicals usage for water treatment. Drinking water regulations demand purification of recovered coagulant before they can be safely reused, due to the risk of disinfection by-product precursors being recovered from waterworks sludge alongside coagulant metals. While several full-scale separation technologies have proven effective for coagulant purification, none have matched virgin coagulant treatment performance. This study examines the individual and successive separation performance of several novel and existing ferric coagulant recovery purification technologies to attain virgin coagulant purity levels. The new suggested approach of alkali extraction of dissolved organic compounds (DOC) from waterworks sludge prior to acidic solubilisation of ferric coagulants provided the same 14:1 selectivity ratio (874 mg/L Fe vs. 61 mg/L DOC) to the more established size separation using ultrafiltration (1285 mg/L Fe vs. 91 mg/L DOC). Cation exchange Donnan membranes were also examined: while highly selective (2555 mg/L Fe vs. 29 mg/L DOC, 88:1 selectivity), the low pH of the recovered ferric solution impaired subsequent treatment performance. The application of powdered activated carbon (PAC) to ultrafiltration or alkali pre-treated sludge, dosed at 80 mg/mg DOC, reduced recovered ferric DOC contamination to <1 mg/L but in practice, this option would incur significant costs. The treatment performance of the purified recovered coagulants was compared to that of virgin reagent with reference to key water quality parameters. Several PAC-polished recovered coagulants provided the same or improved DOC and turbidity removal as virgin coagulant, as well as demonstrating the potential to reduce disinfection byproducts and regulated metals to levels comparable to that attained from virgin material

Understanding Environmental Policy Processes: A Review

Environmental policies in developing countries are increasingly criticised for being predicated on highly questionable assumptions. This presents two challenges. The first is to explain how and why particular types of knowledge get established in policy. The second is to think about how policy processes might be opened up to more diverse forms of knowledge. Understanding the knowledge-policy relationship involves clarifying exactly what policy is and how it is developed, and reflecting on the particular nature of scientific knowledge which plays such a major role in environmental policy-making. Analysing the policy process also cuts to the heart of key debates in social science: why is reality framed and dealt with in certain ways? How important is political conflict over distribution of power and resources? What is the role of individual actors in policy change? Three contrasting explanations of policy change are explored: that policy reflects political interests, that change reflects the actions of actor-networks; and that policy is a product of discourse. The paper addresses the extent to which these explanations are compatible and argues that they can be taken together using a structuration argument, where discourses and interests are seen as shaping each other, and where both are additionally influenced by the actions of actor-networks. The analysis emphasises the importance of agency and suggests that powerful interests and discourses should not necessarily prohibit the emergence of more participatory policy processes: those allowing room for citizen science and the diverse perspectives of different actors

Contexts for regulation : GMOs in Zimbabwe

This paper looks at the regulation of biotechnology in Zimbabwe. It argues that key uncertainties in biosafety debates are context specific; this means that locally-developed, flexible regulatory systems are more appropriate than the standardised, internationally harmonised, solely science-based forms of riskassessment often advocated for developing countries. The paper begins with a brief examination of the development of regulatory institutions in Zimbabwe. It then looks at biosafety regulation in practice through two case studies, field testing of GM maize and cotton, and safety assessment of GM food aid imports. A final section moves to consider the limitations of the existing regulatory process and identifies challenges that exist for effective regulation in a small, agriculture-dependant country such as Zimbabwe

Seeds in a globalised world : agricultural biotechnology in Zimbabwe

Great claims are made both for and against the potential contribution of GMOs to the future of African agriculture. This paper explores this, looking at what biotechnology might mean for agricultural and food production systems in Zimbabwe. It focuses on two key crops, cotton and maize, and argues that choices about possible biotechnology futures have to be understood in relation to trends towards globalisation and liberalisation of the seed industry, and also shifts in the political economy of agriculture, both at home and overseas. Assuming that there is support for some role for agricultural biotechnology in Zimbabwe, and leaving aside questions of regulation, several key choices emerge, linked to four different future scenarios: is it best to rely on market-supply of technologies from multinational corporations? Or should Zimbabwe seek to develop technologies independently? Alternatively, if the latter is unrealistic, what scope is there for the pursuit of a middle position, striking bargains with big corporations and pushing for more locally appropriate forms of technology? Or, finally, are choices ultimately irrelevant with the most likely outcome being that transgenic biotechnology essentially passes Zimbabwe by? Several factors are identified that are key to these different scenarios, these include: technology choice; issues of technology access and ownership; the – as yet uncertain – role of new farmers emerging as a result of land reform and changes in the agrarian economy; the shifting dynamics of seed markets; changing industrial structure and ownership patterns; new economic conditions and trends in international trade relating to GMOs. The paper concludes that these contexts and trade-offs need to be brought more specifically into debates about alternative GM or non-GM futures in Zimbabwe, and elsewhere in Africa, than has happened to date

Improving sepsis care in Africa: an opportunity for change?

Sepsis is common and represents a major public health burden with significant associated morbidity and mortality. However, despite substantial advances in sepsis recognition and management in well-resourced health systems, there remains a distinct lack of research into sepsis in Africa. The lack of evidence affects all levels of healthcare delivery from individual patient management to strategic planning at health-system level. This is particular pertinent as African countries experience some of the highest global burden of sepsis. The 2017 World Health Assembly resolution on sepsis and the creation of the Africa Sepsis Alliance provided an opportunity for change. However, progress so far has been frustratingly slow. The recurrent Ebola virus disease outbreaks and the COVID-19 pandemic on the African continent further reinforce the need for urgent healthcare system strengthening. We recommend that African countries develop national action plan for sepsis which should address the needs of all critically ill patients