Easing the cost of phosphorous removal in AMP7 How will you ensure accurate dosing of chemicals? by Bruce Quilter, Sector Specialist - Industrial & Environmental, WMFTG
Treatment chemicals are the largest cost to water companies. Chemical use lies at the forefront of cost-saving plans as the water industry in England and Wales enters the new regulatory asset management period (AMP7). They also carry a heavy embedded carbon footprint due to the scale of production and transportation they represent.
AMP7 runs from 2020-25 and utilities face challenges on many fronts – reducing customers' bills, eliminating pollution incidents and achieving zero carbon by 2030. Some £5.3 billion is expected to go on improving the environment and of this, £4.5 billion is related to wastewater treatment obligations, with £2.2 billion earmarked for phosphate removal.
The phosphorous removal programme is driven by European legislation and utilities will require a mix of solutions to meet tighter consents, including higher chemical usage. This means optimisation of chemical dosing will drive ongoing efficiencies and cost and carbon savings across plant operations.
All wastewater effluent returned to the environment is subject to stringent standards. Ensuring the appropriate treatment chemicals are used in the correct quantities, and at the right time is the cornerstone of successful plant operation and staying within regulatory law.
Choosing the right technology
Overdosing can lead to unnecessarily high chemical requirements, which, as well as extra cost, compounds higher embedded carbon emissions from chemical production and transportation. In wastewater treatment, it can also lead to high levels of chemicals in the sewer outflow, potentially exceeding regulatory limits.
In contrast, underdosing can reduce the efficiency of treatment processes, also leading to repeated breaches of environmental license conditions and the risk of regulatory fines and reputational damage. Reviewing the performance of dosing pumps at each site is one way of identifying potential cost savings and efficiency opportunities.
Questions when evaluating pump types include:
• Can the dosing pumps handle pressure changes from variable flows?
• Are the pump valves getting blocked?
• What are my energy costs?
• What are my maintenance costs?
Opportunities from meeting AMP7 challenges
Several UK utilities have installed peristaltic dosing pumps as an effective way of controlling coagulant additions necessary to reduce phosphorus levels. Watson-Marlow's Qdos range has a ±1% accuracy range.
Maintenance is another area offering significant savings. Higher demands on chemical suppliers due to the tightening regulations may effect chemical quality.
Particulates in chemicals can cause problems with ball valve seal faces in diaphragm pumps, this may affect pump accuracy and may require ancillary equipment to prevent syphoning.
The reduction in ancillary equipment required with peristaltic pumping systems means they are much less likely to clog, block or leak.
In addition, Qdos pumps provide a reduced maintenance with single, no-tools, ReNu pumphead replacement. This significantly reduces downtime, which is even more important at works where no standby pump exists.
The water industry faces extraordinary challenges on cost and environmental performance over the next five years and beyond. By reviewing total expenditure on chemical dosing with a view to upgrading systems, there are savings and major efficiencies to be had.
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