Background

We are aiming to degrade the blockages in urban drainage systems that accumulate when fats, oils and greases are disposed of down kitchen sinks or drains. Fats, oils and greases are not particularly harmful to the national sewage system when in liquid form, but as the lipids cool down the congeal and harden. The solidified lipid material is highly adhesive and sticks to the interior crown of the pipes, restricting the flow of wastewater and causing the pipes to block. The solidified lipid blockages have been nicknamed “fatbergs”by the media. Bleach and detergent use is only a temporary solution and merely cause the fatberg to develop further downstream. The fatbergs have the potential to lead to SSO’s (Sanitary Sewer Overflows), which have the potential to unleash raw sewage and contaminants such as endocrine disruptors, pathogens and pharmaceuticals into the urban environment.

A fatberg found in the sewers beneath Kingston upon Thames in July, 2013 was estimated to weight 15 tonnes and reached the size of a London bus. The fatberg had reduced the flow capacity of the sewer to 5% of it’s normal capacity and had the potential to spurt raw sewage out of manholes across the whole of Kingston upon Thames. The fatberg damaged 20m of pipes which took Thames Water six weeks to complete and involved the closure of a number of major roads in West London for the duration of the summer.

Water UK estimate that throughout the UK there are approximately 200,000 sewer blockages a year. As many as 75% of the afforementioned blockages are estimated to be caused the inproper disposal of fat, oil and greases. Water UK speculate that the incidence of such blockages is on the increase. The treatment of fatberg blockages costs water companies in the UK millions of pounds every month which is reflecting in the rising cost of water bills in the UK. Key problems resulting from the development of fatbergs include sewer flooding, rat infestations and odour problems.

This problem is not specific to the UK, but is becoming increasingly commonplace in more economically developed countries including the USA and Australia to name but a few. The increasing number of has been linked to the rapid increase in the number of food service establishments in metropolitan areas. Many countries have legal provisions requiring food service establishments dispose of fats, oils and greases through grease interceptors, however, such devices are often insufficiently designed to cope with large volumes of waste material and are incapable of effective FOG separation from the kitchen waste stream.

A related problem we intend to solve is the build up of hair that gets trapped in plugholes in baisins, baths and showers. Hair attracts grease and dirt particulates which build up in drainage systems and restrict the flow of water through pipes. Our project has focused on development of constructs that produce lipase and keratinase enzymes to degrade FOGs and hair. These constructs are designed to sit within a small, under-sink bioreactor that will produce and feed them into the waste system as the sink is drained.