As a result of high levels of manganese present in the water the iron removal filtration stage was also preceded by sodium hypochlorite dosing, which in turn was maintained at a low residual level by redox potential control of dosing. A clean-in-place (CIP) rig with heated feed tank was also supplied to enable regular cleaning of RO membranes.

The original requirement from J Holt Ltd was for a continuous supply of 8 m3/hr of treated water. EWS (UK) Ltd recommended the supply of 2 x RO2268 reverse osmosis plants, each rated at a maximum permeate flow of 5 m3/hr. With a filtered water blend ratio of nearly 1:2, the plant on initial commissioning was able to supply nearly 15 m3/hr of treated water to service with nearly 100% built in redundancy in relation to the RO’s, whilst still offering an acceptable payback to J Holt Ltd.

The compact design of the RO2268 with vertical RO membrane housings meant that a relatively small footprint was required on site for installation. J Holt Ltd supplied bitumen lined bunding for containing the plant and EWS (UK) Ltd off-loaded, positioned, installed and commissioned the plant. As the plant is installed on the roof of the Derby Brewery a crane with 100ft reach was required for the off-loading.

The existing pipework within the brewery used to distribute towns’ main water was reutilised for transportation of the treated borehole water. As much of the pipework was cast iron it was necessary to blend the RO quality water (typically < 20 µS/cm) with filtered borehole water to prevent pipework corrosion.

At the time of the initial installation control of the blend conductivity was manual, with a conductivity meter supplied for indication purposes only. However, closure of a number of nearby sites drawing from the same water table has led to changes in inlet water quality and more recently the 4-20mA output from the conductivity meter has been used to control a modulating valve on the filtered water feed to ensure a more consistent quality of blended water.

Additional ABS and stainless steel pipework was supplied by EWS (UK) Ltd as part of the installation. A Grundfos, vertical, multistage pump with built in invertor was supplied to provide distribution and consistent pressure throughout the brewery. At sites request facility was also provided for optional use of an existing fermenting vessel for additional, intermediate treated water holding tank capacity.

The changing borehole supply has meant a reduction in inlet water quality and subsequently the ratio of filtered water to RO permeate has dropped leading to an associated increase in concentrate flow to drain. Head Brewer Keith Sheard again consulted with EWS (UK) Ltd to see if anything could be done to reduce the water lost to drain.

EWS (UK) Ltd recommended that site consider fitting a third RO plant, treating the concentrate streams from the first two units and suggested that as a result of reverse osmosis being added to the Government Technology List in relation to water recovery it might be possible to gain some tax advantage in relation to capital expenditure. The result was installation of an additional pumping tank system and RO2268 in August 2006.

Overall plant control and indication is provided by a Mitsubishi PLC with Beijers touch screen, colour interface. The Human Machine Interface (HMI) provides superb graphic indication of plant operating condition and simple operator control. The flexibility offered by a PLC and programmable interface has allowed recent plant modifications to be easily incorporated within the existing controls.

J Holt Ltd continue to go from strength to strength and in September 2005 won Gold and Silver medals at the prestigious Brewing Industry International Awards, held bi-annually.