Particle size analysis in primary and secondary waste water effluents

Primary and secondary effluents of three waste water treatment works were analysed for the size distribution of particle mass, chemical oxygen demand (GOD), and phosphorus. Fractionation of suspended solids was done by 0.1-8.0 mu m polycarbonate filters and 32-125 mu m sieves, respectively. Primary as well as secondary effluents exhibited characteristic differences in the size distribution curves. Particle size distributions in terms of particle mass could be represented by a power law function. Automatic measurement of particle size distribution by a laser scanning device (CIS-100) was evaluated. Especially low concentrated waste water suspensions proved to be susceptible to aggregation during analysis. Therefore repeated short time analysis of subsamples is recommended. (C) 1997 IAWQ. Published by Elsevier Science Ltd.