Water suppliers need to monitor and respond to coliforms in drinking water. The long term sustainability of current chemical coagulation practices for water treatment is being questioned for a number of reasons: availability of coagulation chemicals, carbon footprint of transporting bulk chemicals and disposal of sludge. The security of supply and cost of ferric sulphate have been raised as particular concerns in this respect. Increasing demand for phosphate stripping in wastewater treatment and the growth of the demand from countries such as India and China are cited as particular threats. This is counter to the routes of supply which may be decreasing, for example ferric chloride is a by-product derived from steel manufactures' spent-pickling liquor but increasingly this is being recycled in the steel process. There is a lack of clear, consistent information that water companies need for confident planning of future treatment strategies.
This programme helped reduced uncertainty and provided water companies with a validated short and long term view of the coagulant market, an understanding of available sludge disposal routes, and a realistic assessment of viable alternative processes.
Benefits to Clients
Reduction in lengthy and costly investigations to trace the cause of coliforms.
- Conducted a detailed market survey of coagulants - incorporating findings from existing surveys and direct discussions with chemical suppliers.
- Assessed opportunities for, and benefits of, cross co-operation between chemical suppliers and water companies, including, for example, examining lead/delivery times and on-site storage.
- Identified the availability of long-term sludge disposal options using WRc's extensive waste management contacts.
- Assessed alternative process options - including membrane treatment, adsorption/ion exchange processes, advanced oxidation and biological processes (including bank filtration) and also reviewed options for recycle/reuse of coagulants.
The suitability of alternative processes were examined, including:
- Current implementation worldwide and applicability to the UK.
- Development needs to produce practical cost-effective alternative treatment options and probable time-frame.
- Benefits of conjunctive use of these processes with coagulation.
- The ease of implementation of alternative processes within existing treatment streams
- Detailed market assessment of coagulant availability with timelines and cost predictions.
- A practical guide identifying site-specific risk from future limitations of coagulant supply or waste disposal options, and mitigation measures.