Odour Control for Food Processing Plant

A recently installed Chemical Scrubbing System, designed and built by ACWA AIR (UK), has proved to be extremely effective in providing odour control for the effluent treatment plant installed at the Selby food processing factory in the UK.

Greencore Group plc is a leading international producer of convenience foods and ingredients, with manufacturing sites in four countries of the European Union as well as the US. The Company employes some 7,500 people, providing a distinctive approach that combines consumer understanding with customer care and a passion for providing the very best products and services.

The ACWA AIR Odour Control System is designed to ensures the capture of all fugitive odours discharged from the effluent treatment process. At the design stage, United Utilities – who are responsible for operating the system - commissioned ACWA AIR to assess the nature and volume of air from various discharge points and establish the requirement for appropriate covers, vents and hoods to collect and direct odours, via a new ductwork system, to the base of the chemical scrubbing process.

In operation, odorous vents from the bio-filter, sludge tanks and other stages of the effluent treatment process are conveyed to the scrubbing system by two in-line fans. Within the packed tower, odour is removed from the waste gases by scrubbing with sodium bicarbonate and sodium hypochlorite.

The exhaust air entering the base of the scrubber passes upwards through random plastic packing material which provides a large surface area to allow the mass transfer of contaminants into the scrubbing liquor as it flows downwards to the base of the scrubber. The open structure of the packing material minimises the pressure drop of air passing through the scrubber and
prevents solid deposition.

The scrubbing liquor, which collects in the sump at the base of the scrubber, is pumped to the top of the packing material by a recycle pump. The pH and Redox of recycle liquor is continually monitored by a PLC control system which regulates the dosing pumps to maintain the correct concentrations of sodium bicarbonate and sodium hypochlorite.

The cleaned exhaust air from the top of the packing material passes through a demister to reduce any entrained water droplets before being discharged to atmosphere via an emissions stack.