The new EBNet Webinar series replaced our annual Research Colloquium with top-quality, specialist webinars on a range of EB topics. Concluding the 2020-21 programme with “FOG/Fatberg Mitigation and Societal Behaviour – Aspects of Environmental Biotech” were Dr Mar Batista, British Water and Natalia Jawiarczyk, Cranfield University. A combination of views was presented from the water industries’ trade body perspective alongside the latest available research on the topic from Cranfield Water. This provided a forum for extensive discussion about the top challenges in this area and the latest findings underpinning our understanding from the research community.
Dr Batista emphasised the underlying importance of the societal and behavioural factors behind problems with sewage blockages. British Water represents approx. 200 members from the wastewater industry and from this perspective the scale of this issue is clear. There are 370,000 blockages/year and approx. 70% are down to fats, oils and grease (FOG). A single fatberg can be the size of a double-decker bus and result in expense and disruption. Careless disposal of oils down the sink combined with wet wipes – at a rate of 1,400 used per second in the UK – is something that behavioural change struggles to deal with. Thames Water, for example, has 108 km of sewers, 15M customers and 43,500 food service establishments (FSE) to manage.
Major issues surround the current system of legislation and regulation, in that currently no legislation requires FSEs to have grease management systems (GMS) in place. Neither are there agreed standards – necessary before Discharge Consents could be considered. Complicating this is that changing customer behaviour takes considerable time and resources, whilst some FOG will always be unavoidable. However, a start to reducing the polluting content of wastewater – which preferably should always be by segregation at the earliest point – looks imminent with the Sewage (Inland Waters) Bill.
Natalia Jawiarczyk has worked on this issue from the point of view of a research scientist studying the effect of bio-additives on the process of FOG formation (nucleation) and rehabilitation (reducing aggregates). Looking at the FOG within sewers, she first examined the underlying mechanisms of FOG formation – thought to involve saponification (soap creation from fat and base chemistry) and fat deposition (solidification in cold conditions) – as well as the processes of precipitation, aggregation and ageing of deposits. Successfully utilising synthetic sewage to tease out the factors revealed that lipids are the main component and saponification is not the leading reaction. Likewise, temperature has only a limited effect. In fact, it is a combination of free fatty acids (FFA) and starch to form complexes with calcium and phosphate that is the culprit. Microbes first need to degrade the original fats to FFA which can then nucleate with starch to trigger aggregation. These aggregates then grow under favourable conditions. Treatment can be tailored to these different stages, to inhibit nucleation or rehabilitate aggregation, by targeting the carbohydrate-degrading or lipid-degrading microbes/enzymes respectively. This new model of deposition opens up new possibilities.
Looking at this topic, clearly action is required to attack the problem from all angles. Altering human behaviour requires an effort of will on behalf of the customers, industry and various regulators to incentivise and reward effective behaviour. The potential consequences of various possible interventions on side-stream and down-stream processes remain to be discovered as new legislation forces changing practices – a post-webinar conversation topic in itself. Certainly, an evidence-based understanding of the underlying science behind FOG/Fatbergs, combined with the will to act, means that improvements are on the near horizon.