A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in the SEATO Graduate School of Engineering, Bangkok, Thailand.

Thesis (M.Eng.) - SEATO Graduate School of Engineering, 1967

The present and future production of sewage sludges in Bangkok has been assessed. Samples of Bangkok septic-tank sludges and sludges from nightsoil concentration were sampled from collection tankers and analyzed for solids content, pH, alkalinity, volatile acids, ammonia nitrogen, organic nitrogen, grease, BOD5, COD, specific resistance and coefficient of compressibility. The effects of possible sludge treat» ment methods on septic tank sludges were evaluated. Samples of this sludge were subjected to thickening tests, lagooning, sand bed drying and wedge wire bed drying studies, and anaerobic digestion and chemical conditioning treatments. Anaerobic digestion of nightsoil was carried out to give some indication of the feasibility of the unheated process in Bangkok for treatment of primary-type sludges. Characterization and treatment tests showed that Bangkok septic tank sludge was already well-digested on collection. The results obtained for treatment of septic-tank sludge indicated that sludge thickening followed by sand bed drying treatment were most applicable for dry weather conditions in Bangkok. Neither lagooning nor wedge wire bed drying treatments were found to be as efficient as sand bed drying for dewatering of this sludge. Chemical conditioning was found to be effective and, if used before other dewatering processes, would result in improved efficiency of the overall treatment. Anaerobic digestion of septic-tank sludge was not found to be necessary but digestion of nightsoil sludges or primary sludges would be advantageous and should produce an easily-dewatered digested sludge.