Utilities urged to think differently on resource recovery

Whether it is the opening up of the market for energy-producing sludge, the sale of extracted phosphorus or reusing sewer grit, wastewater utilities now have increasing opportunities for resource recovery which they should make the most of, delegates at WWT's Wastewater Treatment conference heard.

The inaugural event, held in Birmingham on January 28thand sponsored by Hach and CDEnviro, explored topics including catchment-based and technological approaches to removing phosphorus, the commercialisation of sludge, screening for grit and rag removal, energy neutrality in treatment works and advanced anaerobic digestion.

Neil Corrigall, head of strategy at Severn Trent Water, outlined the huge economic potential of opening up the market for sludge, saying that his company spends up to £700M annually on sludge treatment compared to £130M on water retail services.  “Of the three areas opening for competition, sludge is the most material from an investor perspective,” he said. “There is far more potential there, but also more at stake if it goes wrong.” He pointed out that with technology changing rapidly, it was important to invest wisely. “If you are going to sink money now into something that is going to last 20 years, you had better be sure that it is worth it,” he added.

Since sludge from small sites is routinely driven to larger sites for processing, it is a natural area for market forces to operate, he said. While at the moment it was only makes economic sense to transport sludge a distance of around 30km, this might well increase to 50km or 70km in future.

Jon Brigg, Innovation Manager at Yorkshire Water, said that the industry had long relied on local agriculture as a customer for its sludge, but it was now time for “systems-based thinking” where the sludge ends up at the company or organisation best able to exploit it. Water and sewerage companies might agree joint venture arrangements where sludge from both their areas is processed at a single site, speakers in the subsequent panel discussion mused.

Nick Mills, Wastewater Innovation Manager at Thames Water, said the idea of “driving sludge all around the country to find the cheapest treatment” is flawed, because transport is the biggest cost involved in sludge treatment. However, he thought it more likely that commercial contractors could bid to run sludge treatment works and make money from the resource.

Phosphorus was a major discussion point at the conference, with presentations covering a number of novel technologies for its removal and a case study on Wessex Water’s pilot programme to remove it from the Bristol Avon catchment via a permitting system. Paul Hickey, deputy director of water quality at the Environment Agency, praised these efforts and called for a change of mindset from water companies on the issue.

“Many of our rivers are still failing on phosphorus, and a lot of them by a country mile. Wastewater discharges are still the primary cause of this,” said Hickey. “Yet phosphorus is a finite resource vital for human life. We need to change our mindset from it being a problem to it being a resource.”

In a session on screening for rag and grit removal, Darren Eastwood, Technical Manager at CDEnviro, pointed out that sewer grit, which can be sorted by size and washed during the screening process, should also be considered a resource. Grit can be re-used as pipe bedding or other filler material rather than sent to landfill, he said.