Surface tension of wastewater samples measured by the drop volume method

Details are given of equipment and a procedure used to determine the surface tension of secondary sewage effluents by a computer-controlled drop volume technique. Results obtained for effluents from several sewage works in Switzerland are tabulated. It was necessary to inhibit biodegradation, using sodium azide, between sampling and measurement. Based on the results, recommendations are made for the measurement of surface tension by the drop volume method.