Fatbergs

Fatbergs are large masses that form in urban sewer systems when fats, oils and greases (FOG) congeal and accumulate with non-biodegradable solids such as wipes, sanitary products, and tampons. The resulting plug can extend for meters and weigh tons, creating severe blockages that disrupt wastewater flow.

Causes and formation: Household and commercial waste poured down drains introduces fats that cool and harden on cooler pipe sections. Items marketed as flushable or wastewater-friendly can accumulate, because they do not readily break down and trap debris as it travels through the sewer network.

Effects: Blockages cause sewer overflows, street flooding and sewer backups into basements, with health and environmental risks. They require costly removal and can damage infrastructure. Removal methods include CCTV surveys to locate the fatberg, high-pressure jetted utilities, and mechanical cutting, sometimes necessitating excavation of sections of piping. Large fatbergs can be removed only piece by piece and disposed of at transfer facilities.

Prevention: Municipal campaigns and public education emphasize disposing of fats in the trash, not the drain; avoid flushing wipes, cotton swabs, and other non-biodegradable products; grease management programs in restaurants; improvements to sewer design to reduce deposition.

Notable instances: In 2017 a large fatberg was discovered in London, described as one of the largest found there, drawing attention to the issue. Similar blockages have occurred in other cities around the world.