Peristaltic technology from Watson-Marlow Bredel is being effectively used to treat chemically disrupted water that helps to prevent 'intersex' fish and other problems associated with pollution.
Male fish exposed to treated sewage effluent especially in the upper reaches of urban river systems have recently been observed to develop female characteristics. Endocrine disrupting chemicals (EDCs) such as natural and synthetic hormones in the wastewater effluent may be causing the intersex effect in male fish.
EDCs are typically found in wastewater at concentrations of less than one part per ten billion and are a minute fraction of all the organic material present. Traditional processes used to treat contaminants found in wastewater are insufficient for completely removing EDCs.
The Environment Agency is collaborating with the UK government and the water industry on a GBP40m national programme to examine EDCs and assess the effectiveness, costs and benefits of their removal in existing or enhanced sewage treatment.
The programme is gathering data from 13 different types of sewage treatment works across England and Wales, including a project at Ilkeston STW in Derbyshire.
Undertaken by Severn Trent Water, the Ilkeston project requires the company to carry out a side-by-side evaluation of three different advanced treatments for removal, and also requires them to carry out fish tests using native roach to determine the effects of different waters on the fish.
The experiments include the comparison of river water, treated sewage effluent and dilutions of treated sewage effluent in tap water.
To make the tap water useable in the sample tanks, the chlorine in the water must be neutralised. Severn Trent specified Watson-Marlow's 520SN/R2 peristaltic pumps for dosing of sodium thiosulphate, which de-chlorinates the water.
The 520 series of peristaltic pumps can be calibrated either by weight or volume, allowing for precise dosing and metering required for the Ilkeston project.
Additionally, Watson-Marlow’s SPX25 hose pumps are also being used to feed the river water and treated effluent to the tanks.
SPX25 hose pumps offer superior suction lift allowing them to be located safely within the work’s perimeter fence with only the suction hose suspended in the river. Also, the pump’s ability to handle solids means that only a simple weed-screen is necessary to prevent weed blockages.
Peristaltic pumps are designed to handle harsh substances well because the chemical is retained completely within the tube. With no valves that can leak or corrode, the pumps can be used for the closely controlled metering of problematic chemicals such as sodium thiosulphate during treatment processes.
The cost-effectiveness of peristaltic technology is also aiding EDC removal.
Philip Bolton, water industry specialist at Watson-Marlow comments that the previous engineering solution for this kind of trial used gear pumps to achieve the flow rate and pressure required, which resulted in a high level of maintenance as well as a complicated pressure regulation system utilising bypass valves.
Peristaltic pumps offer superior results with simple operation and reliable performance. For instance, the reduced requirement for maintenance of peristaltic pumps not only lowers costs but also frees up the engineers’ time for more value-added work.