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Getting to Grips with… FOG and bioaugmentation

Of the tens of thousands of blockages in UK sewer networks every year, almost three quarters are caused by Fats, Oil and Grease (FOG). Here, we look at the case for adding selected strains/mixed cultures to wastewater (bioaugmentation) and how it compares to alternatives such as jet washing

Q&A with Ray Taylor, Chief Technical Officer, Next Filtration

Q: Firstly, why have some water companies been sceptical about using Enzymes?

As with all treatments, any trial needs to be given a fair chance. It’s true that enzymes are a catalyst that break up FOG, but smaller molecules of fat can congeal further down the sewer - or their impact reduced by dilution – hence the perception that what at first appeared to have resolved the problem, has reappeared later. Over the years, albeit with good intentions, there has been plenty of dabbling, but faced with such chronic FOG problems and regulator penalties we are at last seeing some commitment from water companies and their contractors to conduct thorough studies that show how bioaugmentation can bring benefits; not just in one area known for blockages, but at the point of source, and then much further along the network and into the treatment works. Additionally, many water companies have set up successful sewer protection departments to mitigate the impact.
Enzymes have also been introduced to enhance the effect of proteins, but in turn this can enhance surfactants that already take a very long time to degrade. Enzymes have a very different effect on fat compared with bacteria; breaking up long chain triglycerides and liquefying the fat, oil and grease in wastewater, but without actually digesting it.

Q: Has the use of bacteria earned a better reputation?
Similarly, there have been mixed results, which haven’t helped the reputation of bioaugmentation, but now there are products available that aren’t dormant and that have a much higher bacteria count. In my previous roles with water companies and contractors I’ve seen the frustration first-hand that by the time certain bacteria are alive and kicking, the water has already travelled through the sewer network.

The disgruntlement has then been fuelled by being told that there needs to be more time for the bacteria to acclimatize or recover from bacteriocides – and for more to be added – so of course this keeps adding to costs, and unpopularity if results are still inconclusive.
The same can be said about extruded enzymes but even more so due to their limited life of just minutes to days. Unlike bacteria they can’t repair themselves or reproduce when they become damaged.

There is no doubt that when applied correctly, some bacteria can make a positive difference, but I don’t buy the sales talk that like some highly trained battalion on an important mission, their impact can be controlled. For me, bacteria, for all the good they can do in breaking down organic matter into simple compounds, will inevitably take their own path. This potential lack of control then begs the crucial question that perhaps isn’t included in the pitch as to what effect those independent bacteria will have on a treatment works.

Q: What types of alternative are there to bacteria and enzymes?
There are proteins released from heat Stressed Fermentation plus non-phenolic synthetic surfactants. These are small proteins released by living yeast in response to a mild heat shock; HSP Heat-Shock Proteins known as stress exo-proteins. These can be easily applied at source or at any stage of the sewer network or wastewater plant to bring process improvements all through the system, rather than just in one particular trouble-spot known for getting regularly clogged up.

Effluent ammonia can be reduced by 50% and phosphates by 60% - the latter being a hot topic because of regulatory changes that see wastewater treatment plants requiring large volumes of ferric chloride. Like any shortage, the one thing that is certain is a price-rise, so with around 95% of ferric chloride demand emanating from the water and municipal wastewater sector, looking at alternative more cost-effective ways to treat FOG is a must if costs are ever to be brought down. Welsh Water, for example, respond to around 2,000 blockages a month at a cost of £7M every year. Like all water companies, I’m sure they would like to make a big dent in those numbers, rather than see it as being the norm.

Q: What then are the main costs when trying to combat FOG in sewer networks?
Jetting and vac trucks are certainly effective – but the measures are often temporary, expensive and don’t solve the ongoing problem.

It’s also staggering to think that more than 50% of a treatment plant’s electricity bill is purely down to the use of blowers. With a population of around 150,000, Cambridge, for example, isn’t even in the UK’s top 50 cities, yet a treatment works at a place of this size will have an annual electricity bill of half a million pounds – 55% of which will be from the blowers. A formulation that can reduce air demand must have potential for a return on investment.

There are also the inflated energy costs at pumping stations affected by FOG, not to mention the maintenance of cleaning the rising main and the non-return valves – and that’s before you’ve counted emergency callouts and fines for incidents from flooding. It’s no wonder that more water companies are looking closely again at bioaugmentation.

Q: Are there positive signs of change?
A counter-argument or concern at the moment is that finding that winning bioaugmentation formula will remove the now valuable resource of FOG from the system – but I recently worked with a water company and a food outlet where it shows how a win-win-win is possible for all parties.

The blockage problem at the food outlet was an historic one – a build-up of FOG, blockages, overflows, general unpleasantness and a great deal of money to put it right – only to see the same
old problem inevitably return. The water company worked hard on its relationship with the food outlet, who eventually bought a highly effective grease trap. They now keep the grease as biofuel for their vehicles – and by the water company adding, in this case a protein to the wastewater, the build-up of FOG has been eliminated.

The point here is that the local problem has been addressed at source, rather than always just focusing on the pumping station, which is now in better shape than for many a year. The protein mix has successfully contributed to getting more air into the water and bringing COD levels down. This in turn is better news for the treatment plant, which still receives its sludge load that can be treated anaerobically for green energy - offsetting the direct biodiesel route from pumping station reclamation.

This aspect of treatment proves that you don’t necessarily need to jet first or close an asset down to add solvent and then pay for disposal. Call-outs and maintenance costs can be reduced, screens are kept FOG-free and there is also less energy required to run network and treatment pumps.

Furthermore, Surplus Activated Sludge (SAS) is reduced (typically by around 15%) – and the quality of final effluent also increases. The numerous benefits are ready and waiting.

-This article appears in the March 2019 issue of WWT magazine.

Topic: Sewer Networks
Tags: Fats Oils and Grease , sewer blockages


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