A rising demand for tea and coffee papers increases production at Union Papertech’s paper mill in Lancashire.
A treatment plant extension was specified as this increase in production, together with substantial water savings in the paper making process, was expected to increase BOD (Biological Oxygen Demand) concentrations that would exceed their current discharge levels.
In addition to increased production, Union Papertech wanted better efficiency in their wastewater treatment, plus it had to be treated to a standard that could be discharged safely into the local watercourse, River Roach. Water used in the production process is also extracted from the river, so recycling the treated wastewater back into the local environment where it originally came from is the ideal solution.
Union Papertech have achieved other efficiencies, for example reducing the amount of water used in the production process. However this means that the actual wastewater produced has a higher overall concentration of soluble, readily biodegradable organic material.
The discharge consent standard had to be 45 mg/L Suspended Solids. Prior to introducing their client to WPL, the consultant spent 4-5 months investigating various technologies available that would fit the client’s requirements. Finally, the consultant recommended the WPL solution to Union Papertech for the following reasons:
· Capital cost was competitive
· Treatment process was more robust and reliable than alternatives
· Installation would be simple allowing the existing plant to remain
· Small footprint - the new system only equates to an additional 25% footprint
Ursula Kepp of Patrick Nolan Consulting Ltd said, “Analysing a number of potential solutions, I concluded that the solution from WPL was the best to accommodate expected variations in effluent concentration and volume at a comparable small footprint.”
The HiPAF SAF (Submerged Aerated Filter) is a biological process, rather than a physical process such as filtration. This means that in order to work effectively, bacteria needs to grow inside the unit to break down and process the wastewater. They need nutrients and air, and in this particular case the nutrients have to be added to the process, so a dosing system will be used to incorporate the right nutrients. Air is supplied by diffuser into each segment of the biozone from air blowers housed in a separate kiosk.
The new plant extension has been installed downstream of the existing DAF treatment plant and consists of three steel SAF (Submerged Aerated Filter) units in parallel streams, using a flow splitter to separate the flow in. After treatment the flow is then combined for tertiary treatment to remove any remaining suspended solids using a WPL Microscreen before discharge in to the local watercourse.
A walk-in kiosk is provided to house the system controls and is easily accessible for monitoring and maintenance.