Chemical dosing in wastewater treatment is required to remove impurities, treat contaminants and improve the efficiency of the treatment process, but running pipework systems for the dosing of specific chemicals carries its own challenges.
Phosphorus removal, which forms a significant part of the Water Industry National Environment Programme1 (WINEP), is also putting the industry under pressure with legally binding targets2 set for an 80% reduction in total phosphorus pollution from wastewater treatments by 2038 to help safeguard waterways.
It means the use of chemicals is therefore intrinsic in the treatment of industrial water and wastewater, but the transportation of such chemicals carries an element of risk, especially in a single pipe system where a leak can pose significant safety and environmental dangers.
David Thomas, Head of Technical Support Services from Aliaxis UK, looks at the use of dual-containment pipe systems to safely carry chemicals in treatment plants, and the difference a chemist can make in ensuring that the system’s materials are compatible with the substances being transported.
Today, the use of chemicals in industrial and wastewater treatment is extensive with chemical dosing used to give a precise injection of specific chemicals to remove impurities, control odours, adjust pH levels, disinfect water, and improve overall treatment efficiency.
Phosphorus is removed from wastewater through chemical precipitation, adding metal salts like iron or aluminium, which causes dissolved phosphate to form insoluble solid precipitates which are removed through sedimentation or filtration.
A dosing rig can be a significant distance from the operation site making safe chemical transportation vital. Flexible hoses are used extensively in wastewater treatment, particularly in situations that require flexibility for awkward layouts or to handle movement. However, the threat of environmental fines due to spills, plus safety issues for people walking nearby, means the use of more rigid, specialised dual-containment hoses is becoming a big part of AMP8.
The double-layer design features an inner pipe that carries the flow and an outer, secondary pipe that contains any potential leakage from the inner pipe.
When made from corrosion-resistant materials, such as PVC-U, as is the case with our fully-engineered, dual-contained system Guardian, such pipework can offer superior chemical compatibility and a longer service life.
However, the chosen material must be compatible with the chemicals to be carried, with consideration also given to the corrosive nature of ancillary agents, in order to prevent premature degradation, costly failures and safety hazards.
The material must also be compatible on the outside, as electrical cables and fillers can also present a detrimental effect on external compatibility.
Therefore, knowing the chemical properties is essential when selecting a material that is resistant to degradation from the specific substances being transported.
Technical teams and in-house chemists, such as our own chemist, can provide project-specific advice, including consideration of any ancillary agents that could come into contact with the pipework, advice on initial designs and specifications, installation guidance and on-site support. They can also advise on more unique applications, as well as perform a material safety data sheet review to ensure the right solution is chosen.
Chemical Resistance Guides also play a part in the selection of the right pipework. Such a guide can help determine the compatibility of system materials with a multitude of chemical substances.
Using a chemist’s knowledge can help ensure material compatibility, promoting the integrity and lifespan of the pipe system so that chemicals do not degrade the pipes, valves and seals over time.
As pressures increase for industrial and wastewater treatment sites to provide extra reliability, dual-containment pipe systems are therefore being seen as offering a failsafe barrier against leaks, critical for environmental protection, employee safety, and regulatory compliance.