A small works treating a DWF of 848m³/day and a FFT of 27l/sec. The works comprises screening and grit removal, conventional primary settlement, Two high-rate plastic filter media primary filters(4.5 m deep) followed by humus settlement, and a conventional single blast furnace slag media secondary filter(1.8m deep) followed by humus settlement.

The works receives trade effluent from an ice cream manufacturer which discharges significant loads in the period June to September each year.

The discharge to the works occasionally exceeds consent but even when within consent leads to a deterioration final effluent quality. In previous years this has led to occasional sample failures of the final effluent but in 2005 this resulted in the works failing for the calendar year. Any future failures would therefore increase the risk of prosecution by the EA.

The plastic media in the primary filters have had significant red fungal growth since their commissioning and the secondary filters had a significant film growth in June 2006.

To enhance the performance of the works to ensure that the works did not suffer any EA sample failures during the ice-cream peak production period.

Initial sampling and analysis work identified the bacteria formulation that would remove excessive film growth from the filters and reduce the BOD/COD thus allowing the high-rate filters to handle the additional load whilst improving nitrification. This would ensure that the EA final effluent consent would be met at all times.

A Bio-Augmentation unit was installed on 5th July 2006. The bacteria dose rate was 250g/day and was carried out with 2 breeding cycles/day, dosed before the primary tanks. Weekly attendance by an independent operator was carried out to ensure optimum performance and regular liaison between technical staff occurred.

To enhance the performance of the works to ensure that the works did not suffer any EA sample failures during the ice-cream peak production period.

The photographs below, left to right, show the filter bed original condition, after one week of treatment and after two weeks. The pictures clearly show that the fungal growth on the plastic media was eliminated within two weeks of Bio-Augmentation deployment, and the film thickness of the secondary filter was observed by the site operator to be the least that he had ever seen. We would also expect to see a decrease in sludge production.

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The table below shows the analysis results during August 2005 and August 2006. The Bio-Augmentation unit was deployed on the 17^th July 2006.

From the table below it can be seen that the crude sewage analysis is very similar for 2005 and 2006. The results show a significant improvement in all parameters throughout the treatment process and during the time the Bio-Augmentation was in use a consistency in final effluent quality was in evidence at all times. This had not occurred in previous years and highlights the technology's ability to deal with high-strength shock loads.