A review of existing and proposed sludge management practices in local authorities

Abstract

Local Authorities in Ireland have to treat and dispose of sewage sludge produced in wastewater treatment plants in their functional area which totalled 45,590 tonnes of dry solids in 2004. Eighty six per cent of this sludge is currently recycled to agriculture. This dissertation examines existing and proposed sludge management practices in Local Authorities and outlines weaknesses in the system and proposes measures to remedy these weaknesses. A detailed questionnaire was carried out by telephone and found that twenty-nine Local Authorities were recycling some or all of their sludge to agriculture. Ten of these Local Authorities were applying raw untreated sewage sludge to agricultural land, which amounted to 9,724 tonnes of dry solids annually or 21.34% of the total sewage sludge production in the country. Some of these Local Authorities have no record of where this sludge was disposed. A further 4,780 tonnes of dry solids was sent to landfill of which 3,543 tonnes received no form of treatment. A substantial number of Local Authorities are not complying with statutory obligations in relation to completion of sludge registers and composite sampling for reporting purposes. Twenty four Local Authorities are proposing to install thermal drying for sludge treatment. Consultants have stated that this type of sludge product is the most versatile.