No abstract

Sludge produced from a trickling filter effluent treatment plant dedicated to the treatment of brewery wastewater was flocculated with cationic polyelectrolytes and dewatered by centrifugation to produce a cake of around 16% (w/w) solids. This cake was mixed with spent grains, shredded office paper and straw to produce an initial mix of 34% (w/w) dried solids with a carbon : nitrogen ratio of 21:1. Temperatures of over 45°C were achieved for around 9 days in a purpose built, laboratory scale, composting unit equipped with temperature and aeration control. Dried solids (DS) were increased to about 65% (w/w) and the volatile solid fraction was reduced from 80% to 60% (w/w) of DS by microbial degradation. The compost was rich in nitrate and phosphate and was used as a peat substitute in qualitative, comparative growth trials where geranium and tomato plants were successfully grown.

This paper details the characterisation of sludge produced from a trickling filter effluent treatment plant dedicated to the treatment of brewery effluent and reports on centrifuge trials for thickening and dewatering it. Characterisation of the sludge revealed that the total solids content was low and variable, at 2-2.5% wlw dried solids (DS), and that the sludge exhibited very poor settling characteristics. A study of the rheological properties of the sludge indicated that at around 2.5% wlw DS.the sludge could best be modelled by the Hershel-Bulkley equation.The variation in rheological properties with solids concentration was measured on samples thickened in the laboratory. Large scale dewatering of polyelectrolyte conditioned sludge was carried out using an Alfa Laval decanter centrifuge in order to obtain cake suitable for further processing or disposal. Operational and dosing conditions were varied and a cake with up to 25% wlw DS was produced using cationic polyelectrolytes Zetag-87 & CT85.