A wastewater treatment plant in North West Sussex faced the problem of disc filters clogged by ferric salt and a consequent risk of pollution. ATAC provided a rapid and reliable solution by installing four MITA cloth filters upstream of the existing systems. This made it possible to drastically reduce suspended solids and maintain regulatory compliance. The solution proved to be extremely efficient, requiring minimal maintenance for over three years, and even allowed for the relocation of the filters to another problematic site.
The North West Sussex treatment plant in this case study is responsible for managing flows for a population equivalent of about 125,000, including a city and the surrounding areas of Gatwick Airport. The site was equipped with pre-existing disc filters, which constantly received flows previously treated with ferric salt dosing.
The ferric material proved to have a tendency to clog the small pores of the disc filters.
This problem required frequent chemical cleanings with aggressive solutions like citric acid. However, the use of these acidic solutions caused the deterioration of the filters’ rubber gaskets, allowing water with suspended solids to bypass the filtration system. Consequently, the site was at a constant risk of polluting the local watercourse. ATAC’s client required a rapid and reliable solution that could guarantee a final effluent with a suspended solids concentration below 10 ppm, starting from an inlet that could reach 35 ppm from the primary sedimentation tanks.
To address this critical challenge, ATAC, an Axius Water company, proposed and installed four MITA WT pile cloth filters, part of Axius Water. This technology is renowned for its excellent performance in solids removal and for its minimal life-cycle cost in tertiary wastewater treatment. They are versatile systems suitable for both industrial and municipal wastewater, and in some cases, even for stormwater.
Their innovative design combines the principles of surface filtration typical of micro-screening with depth filtration, characteristic of sand filters, while maintaining extremely low investment, operating, and maintenance costs. MITA cloth filters are also known for their low energy use, as filtration occurs by gravity and backwashing requires energy only in its specific phase, without interrupting operational continuity.
ATAC, the national distributor for MITA WT and part of Axius Water, strategically positioned these filters upstream of the existing disc filters to pre-treat the flows and remove the solids containing ferric salt, thus significantly lightening the load on the downstream systems. To support the operation, two 6-inch diesel pumps were used, configured to distribute a flow rate of 140 l/s uniformly among the four cloth filters via custom-designed distribution chambers.
The installation process was managed and carried out with great expertise by ATAC’s in-house project team, which includes design specialists and back-office staff. The speed and efficiency were evident: in just seven working days from receiving the purchase order, ATAC mobilized resources, installed, and commissioned the four cloth filters.
The setup included all necessary components: the distribution chambers, ATAC diesel pumps, control panels, and piping. The client immediately saw the desired results in terms of effluent quality.
The MITA WT filters have been operating successfully for over three years, demonstrating remarkable reliability. This has allowed for a drastic reduction in suspended solids and the maintenance of regulatory compliance. The solution has proven to be extremely efficient, requiring minimal maintenance for over three years.
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