Treatment of Wastewater from Car Washes Using a Biofilter

Abstract

This project investigates the treatment of wastewater from two car washes using a biofilter of peat and carbon-containing ash. An evaluation of the efficiency and waste handling of the filter material was done from an environmental perspective. The biofilters were used during 2 and 4 years respectively. The treatment included an oil separator and a peat/ash biofilter. The main function of the oil separator was to reduce the amount of oil in the wastewater. The peat/ash biofilter was used as a second step of the system to treat mainly heavy metals. A comparison with the guiding values for wastewater from car washes in the municipality of Kristianstad showed that this type of filter works well. Wastewater from car washes may contain many different unhealthy and environmentally dangerous substances such as surfactants and aromatic compounds. More tests are needed to investigate if the treatment method reduces such parameters from the wastewater as well. After usage the filter is considered solid waste and is to be classified and handled according to that. Classification of the filter as waste requires knowledge about the content of environmentally harmful substances in products used in the car washes. As the content of non-analyzed substances in the filters was unknown, combustion was regarded to be an environmentally good way of disposing the filter material as both energy and ashes are recycled.