A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 1999

The study conducted was an effort towards estimating the reuse potential of secondary treated wastewater for non-potable applications in an university campus. An estimated 1500 m3 /d of potable water is consumed in AIT, which is provided by MWA at the rate of 14.98 Baht/ m . A water consumption audit of the academic buildings in AIT revealed high m3 /m2 /d values of the 0.04, 0.022, 0.018 and 0.022 at the AFE, ETl, ET2 and, CIM buildings. A water audit of the AIT center revealed a consumption figure of 69 L/cover for the restaurant, which is higher than the most lenient Thai standards of 45 L/cover. No water meters are available in the residential areas of the campus thus providing insufficient data to analyze the nature water consumption or assess loss due to the leakage. A pilot-scale tertiary treatment plant operated in two modes to provide treatment to the effluent. The first mode consisting of coagulation, flocculation, sedimentation followed by dual media filtration gave an effluent quality suitable for urban non-potable reuse applications as per specified by the USEP A reuse guidelines. The treated effluent showed a pH range of 7.6-7.9, turgidity in the range of 1.75-2.25 NTU, color less than 5 Hazen units. Total solids, suspended solids and total dissolved solids showed reduction of 35, 83 and 33 % respectively. Whereas the BOD5, COD and TOC values were obtained in the range of 7.4- 10.5, 12.2-24.8 and 11-14 mg/L respectively. In the second mode MF was used in three schemes. Scheme I where MF was used as a polishing unit for the unit operations in mode I gave the best results providing near potable quality water. On comparing MF with dual media filtration in Scheme II the use of the prior gave a better quality effluent. Turbidity values in the range of 0.7-0.9 NTU, total solids, suspended solids and total dissolved solids in the ranges of 987-1150, 0-1 , and 951,1131 respectively, COD and TOC values in the ranges of 10.5-14.2 and 7-8 were obtained by using MF. The scheme III where MF was the lone unit operation did not give satisfactory results giving the least filter run of 118 h prior to chemical cleaning. A Full-scale treatment plant design undertaken gave a basic treatment plant cost of 14 M Baht and a operation and maintenance cost of 7.2 Baht/m3 . A leakage detection program needs to be undertaken at the earliest on the campus in order to cut down the sever cost of water procurement.