Power use at municipal wastewater treatment plants: recommendations for greater efficiency: case study of South Tipperary County Council facilities

Abstract

Until very recently power management has not been much of a concern to those people managing wastewater treatment facilities. Latterly, however, much has been written in the media and elsewhere about “the end of cheap energy”. This has focused minds on the fact that a lot of energy is wasted and could be more efficiently utilised. Efforts are increasing in all industries to improve energy efficiency in tandem with process optimisation and the same is true of the wastewater treatment industry. Electricity consumption was analysed at eight wastewater treatment plants in South Tipperary and was found to be in the range 1.76 - 8.09 kWh per KG BOD treated, or 36 - 175 kWh per population equivalent and year. Such a broad range of treatment efficiencies may suggest that there is a large amount of scope to improve the performance of some plants with respect to electrical energy efficiency. Cashel wastewater treatment plant (WWTP) was used as a model to see if it was possible to improve the energy efficiency of a plant with no capital investment. The initial treatment efficiency was found to be 2.83 kWh per KG BOD treated or 61.95 kWh per population equivalent and year during the month of November 2005. After implementation of a range of efficiency improvements, these treatment parameters were measured again in March as 2.33 kWh per KG BOD treated or 51.08 kWh per population equivalent and year. Final effluent quality was maintained throughout the study.