Assessing the Efficacy of Dissolved Ferric Chloride Conditioner on Dewaterability of Sewage Sludge

Abstract

The aim of this study was to investigate the efficacy of dissolved ferric chloride conditioner on dewaterability of sewage sludge. A funnel- shaped drying bed of 420mm surface diameter, 340mm vertical depth, 25mm diameter discharge pipe was used in this study, and containing 75mm thick sand layer, grain size 0.20mm – 0.60mm diameter. On this layer was placed 200mm thick sewage sludge thoroughly mixed with ferric chloride solution, introduced into the drying bed and filtration allowed to take place. Discharge from the control experiment was further and faster with maximum discharge of 201m³ at the 400^th minute. Repeating the experiment on the 2^nd, 3^rd, 4^th, 5^th and 6^th days, maximum discharges of  78cm³, 41 cm³, 40 cm³ , 39 cm³ and 39 cm³ were experienced at the 300^th minute for the 2^nd day, 200^th, minute for the 3^rd and 4^th days and 180^th minute for the 5^th and 6^th days respectively. Efficacy retardation factors were 2.577, 4.902, 5.025, 5.154, 5.154 for the 2^nd, 3^rd, 4^th, 5^th and 6^th days. Minimum and maximum instantaneous inhibition coefficients were found to be 0.52 and 0.78 which indicates high inhibition. The result of specific resistance to filtration  show that it increased tremendously when the salt is stored in solution. Specific resistance to filtration are , , , ,  and  in the 1^st, 2^nd, 3^rd, 4^th, 5^th and 6^th days respectively. There was no consistent increase in these values, but seem to be fluctuating. This anomalous behaviour is a limitation in the work of  Ademiluyi and Arimieari, and because of that, their model is not so good in the prediction of specific resistance to filtration.

http://dx.doi.org/10.4314/njt.v34i2.26