Pre-treatment of municipal sludge before de-watering

Traditionally, wastewater and slurry is separated using centrifugal technology to de-water the slurry.

However, it was found that by pre-treating the waste with Neutralac® SLS45 before de-watering, its high alkaline content sufficiently neutralises the wastewater so it can be recycled back into the water course, and the slurry is cleansed and disinfected for use as farm fertiliser.

The organic matter is enhanced for farming purposes due to the lowering of acidity, the removal of pathogens and subsequent high nitrate qualities.

The chemical reaction of Neutralac® SLS45 creates a sterile alkaline environment in excess of pH12 for sustained periods, effectively disinfecting the sludge by killing the wide spectrum of pathogens listed above.

Furthermore, the cost reductions in transporting both the treated water and disinfected slurry become significant while, at the same time, closing the environmental recycling loop. The disinfected farm slurry also offers an income stream previously not always available to utilities companies as it can then be sold to farmers.

Disinfected slurry becomes fertilizer

A spokesperson for the utilities company commented:
‘We have been through a stringent process and our selection of Neutralac® SLS45 was not taken lightly. Our tests have shown a significant improvement in the lowering of acidity of waste, and the improvement and relevance of the resultant slurry as a fertiliser.

‘Also, it became apparent we required a tailored solution, including custom-built storage and dosing rigs, which we could integrate into our current system without too much disruption. The Lhoist team has worked hard to help us create this and integrate it into our SCADA computer-controlled system.’

Installation of storage tanks

Partnering with PCM, leading and recognised suppliers of chemical dosing equipment to the utilities industry, Lhoist is also installing 15 and 40 tonne dosing tanks on all four sites.

‘The project was not just about choosing the best liquid lime for the job, important though that is. We needed a liquid lime supplier who delivers on all fronts, including understanding our issues and setting up the treatment processes.

‘This integrated, sustainable solution closes the environmental loop while improving our processes and making significant cost savings,’ concluded the spokesperson.