Households, businesses and horeca in the Netherlands are still flushing too much fat into the sewer system. Even though used fat – such as from deep-frying or baking – can simply be put in the refuse bin, municipalities and Water Authorities still often find it in the sewers and at wastewater treatment plants. Sewers get clogged, lifting stations get stuck, and the treatment processes are disrupted. Tackling fat accumulation in sump pumps, discharges and sewers is a serious part of the operational activities of municipalities and wastewater treatment plants.
An existing microbial product offers a means of addressing this fat accumulation, without having any adverse effects on the composition of the wastewater. In addition, the receiving wastewater treatment can in principle continue operating properly. This is the conclusion of recently completed research within the TKI Water Technology programme of the Top Sector Alliance for Knowledge and Innovation.
High cost to society
Deposits of fats, oils and grease (often referred to as FOG) clump together and settle in pumping stations for example. If this causes blockages or the failure of system components, it can entail high (societal) costs. Besides the downstream from the discharge point, these problems can occur in the entire sewer system. To illustrate: it costs a Water Authority almost 3 euros to remove one litre of fat from the wastewater. That is twice the cost of the fat in a shop.
Microbial treatment of fat accumulation
Any approach has to begin with preventive measures to control fat discharges into the sewers. If too much fat nonetheless gets into the sewer system, municipalities sometimes are obligated to take curative measures. They can make use of Microcat®-BioPoP: a microbial product that is sold as a means of countering fat accumulation in pumping stations, discharges and sewers. The product has a solid, cylindrical form, that slowly dissolves in water. The microbes and enzymes that it contains are released and biologically break down the fat into water and CO2. The product is employed at several sites in the Netherlands and elsewhere to prevent fat accumulation in industrial and municipal (sewer) network systems. In practice, for instance at the municipality of Zoetermeer, this has resulted in fewer nuisance reports and lower cleaning costs. The question that arises for the Water Authorities is what effect such a product would have on the operation of the wastewater treatment plants. This question was researched in a partnership within TKI Water Technology.
No adverse effects
To discover whether the Microcat®-BioPoP product might have any adverse effects on the operation of the wastewater treatment, research was done into the composition of the wastewater (beaker experiments) and the treatment efficiency (bioreactor experiments) when the product is used. Fermentation tests were also conducted to measure the possible impact on biogas production. Non-target screening and suspect-target screening was carried out to determine whether the product’s use resulted in the release of any undesirable organic compounds. All these research methods indicate that even though the microbial product changes the composition of the wastewater, it has no negative effects on the biological processes in the wastewater treatment, nor on the production of biogas. No release of additional organic micropollutants was shown. Given that the application of the fat-breakdown product in the sewer system is usually limited to a partial stream of the total wastewater treatment influent, it can be concluded that the Water Authorities need not anticipate any adverse effects in their operations and that municipalities can make good use of the product in their battle against fat.
The TKI ‘Sewage fat solution’ project was conducted in collaboration with Macero, QM Environmental Services, the Municipalities of Oss and Zoetermeer, the Aa and Maas and the Schieland and de Krimpenerwaard Water Authorities, and KWR Water Research Institute. This activity was co-financed by the PPS funding from the Premium of Top Sector Alliance for Knowledge and Innovation (TKI) of the Ministry of Economic Affairs and Climate Policy.