Page 44

TOPPER

A market for sludge AS CURRENT METHODS OF SLUDGE MANAGEMENT COME UNDER INCREASING PRESSURE, PRIVATISATION COULD SEE THIS WASTE PRODUCT BECOME A VALUABLE RESOURCE, PETER HAYES FROM CDENVIRO TELLS LAPV.

T

CDEnviro's S:Max system can help processors eliminate blockages and minimise downtime.

he sludge produced when treating wastewater may seem like one of the least desirable or valuable materials around, but with diminishing land available for disposal and authorities working to remove the regulatory red tape, that could be about to change, according to Peter Hayes from waste management specialist CDEnviro. The UK’s population is expected to grow over the next 50 years with an associated increased demand on infrastructure. This will place enormous strain on the current methods of sludge management. Water UK reports that around 80% of sludge is currently recycled, 18% disposed of through thermal destruction, and 0.7% goes to landfill. However, continued urbanisation and increasing city sizes mean that the cost of transporting sludge to suitable land for recycling will rise to unsustainable levels in the near future. As a consequence, demand for suitable land will increase dramatically and landowners will be able to charge significant disposal fees.

44 LAPV December 2017

‘Simply turning to landfill for disposal is not a viable option as the costs per tonne will quickly become prohibitive – especially in the sludge’s untreated semi-liquid state,’ explains Peter Hayes. ‘Managing sludge will, therefore, be a key driver in the wastewater industry, especially when planning new-build treatment works or refurbishing plants.’ The need to find new ways to deal with sludge could lead to large-scale privatisation, along with an increase in cost to the taxpayer, as private operators invest in sludge management facilities and take on the process of sludge management. ‘Despite its unpromising origins and semi-liquid state, sludge can be used as fuel for energy generation or to fertilise fields,’ Peter explains. ‘With the right treatment, rather than being seen as a costly waste product, sludge should, in fact, be seen as a potentially valuable resource. A market for sludge trading is predicted to be in place before 2020.’ If the sludge trading market is to become a feasible reality, however, cost-effective treatment options are essential. ‘Typically, sludge is collected at satellite sites and transported to a central facility for processing in tankers,’ says Peter. ‘This imported sludge needs screening to remove rag and grit. Rag varies from organic matter to solid plastic, all of which needs to be removed otherwise it clogs systems downstream. Removing this material early in the process is the best method to protect plant and equipment further down the line.’ Grit also collects in the sludge, largely as the result of runoff from road surfaces. ‘The grit will be screened throughout the process, but it is the 75-300µm particles that typically get through and cause

LAPV December 2017  
LAPV December 2017