Reuse of redundant gravels and phyto-conditioned sewage sludge

Abstract

Blackburn Meadows is one of the largest waste water treatment works and landfills under Yorkshire Water’s operation. The site treats sewage from over 450 000 people and produces more than 20 000 t of sludge annually, which requires disposal. The sewage sludge is disposed of by means of a number of methods, including incineration followed by landfilling of the ash and direct disposal to landfill. Between 2010 and 2014, the construction and restoration of landfills on the site required approximately 6000 m3 of gravels and 18 000 m3 of topsoil. This paper describes two sustainable examples of material recycling – redundant filter bed gravels from another local site were crushed for reuse in landfill construction and sewage sludge after in situ phyto-conditioning was reused for landfill restoration. Atkins designed the requirements for the reused materials to achieve the most cost-effective specification, which resulted in cost savings of more than 48% for the basal leachate drainage blanket and more than 79% for the restoration layer. Phyto-conditioned sewage sludge is demonstrated to be supporting vegetation on the restored landfills. The construction and restoration of landfills at Blackburn Meadows provided an outlet for approximately 24 000 m3 of materials that would otherwise require disposal by other means.