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Grit removal - a totex opportunity

A good model by which the water industry can test the total expenditure (totex) model is the process of grit removal in wastewater treatment. By removing more, and finer, grit at the inlet works, there are downstream gains in terms of reduced damage to equipment, and less clogging of channels and downstream processes such as aeration, which causes process and energy inefficiencies.

The 2016 WaterBriefing AMP6 & Totex water industry survey took the example of grit removal to explore viewpoints and attitudes to totex in practice, and the results turned out to support a view of the 'disconnect' between the opportunities of a totex model and the reality of practice. Nearly all relevant respondents agreed that inadequate grit removal could be reducing overall efficiency of their plant, and that grit abrasion impacts on wear, and replacement of parts, treatment capacity and effectiveness of biological treatment. Yet, at the same time, most people also viewed grit removal as an area of operation where settling for a compromise in the level of protection is accepted.

There was a strong indication that water professionals believed upgrading grit removal systems would help to meet totex objectives in AMP6 and beyond. Both in the UK and elsewhere in the world - and particularly in the US - the industry standards for grit removal have remained the same for many decades. However, technology now exists that far outperforms these standards that could protect downstream processes, save costs and optimise performance. Only those operators prepared to go beyond the standards, embrace innovation and evaluate an investment in advanced grit removal in terms of a totex model will reap the benefits.

Seeing totex as an incremental journey, rather than a distant prize, may help progress, and the example of grit removal offers some evidence of the green shoots of change. Several UK water companies are undertaking grit sampling studies across the UK, which are already showing promising results, and several are also conducting pilot trials of the HeadCell® advanced grit management system at selected wastewater treatment sites.

The HeadCell® is well established in the United States and has been successfully protecting US wastewater treatment plants such as the one at St Bernard, Louisiana from grit abrasion and deposition for many years, but the US industry already understands that damage that grit can do - and the cost of that damage. If the UK water industry wants to embrace totex and cut its long-term spend, removing more grit would be a good place to start.

Keith Hayward, Hydro International

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