An ecological study of the meiofauna of slow sand filters, with particular reference to the oligochaetes

Abstract

In this thesis an examination is made of the ecology of the meiofauna in a slow sand filter used for the purification of river derived water for industrial and domestic supply. The physical and operational features of the filter are described in relation to the biology of the organisms inhabiting it. Problems encountered with sampling the meiofauna of such a system are discussed and a criticism of the sampling methods employed is presented. A discussion is made of the uses of total particulate organic carbon as a parameter for characterising the biomass changes in the system. An evaluation of the horizontal and vertical distributions of the meiofauna in the filter is presented. Similar observations are made regarding the distributional heterogeneity of the organic carbon in the system. Special attention is directed to the oligochaetes present. A relationship is determined between length and dry weight and also segment number and dry weight of Enchytraeus buchholzi, the only actively sexually reproducing oligochaete worm present. The segment number - dry weight relationship is exploited to obtain quick estimates of the dry weight of the worm for biomass estimates. Seasonal changes in population abundance of the meiofauna are presented. The need to obtain estimates of parameters not easily measured in an operational filter is discussed. The design and functioning of an experimental small-scale filter is described and criticised. A method is detailed for obtaining interstitial water samples without them coming into contact with air. An account of a micro-Winkler oxygen analysis is given. The results of redox potential measurements and dissolved oxygen analyses, made in the pilot filter, are presented together with a discussion on the insight which these measurements give as far as bacterial activity in the filter is concerned. A discussion is made of the ecology of the meiofauna in slow sand filters and further suggestions for research investigations are made.