A thesis submitted in partial fulfillment of the requirement for the degree of Master of science

Thesis (M.Sc.) - Asian Institute of Technology, 1992

Waste stabilization ponds (WSP) may be affected by toxic compounds which inhibit bacterial activity and reduce the rate of biodegradation of organic matter. Research was conducted to evaluate the toxic effects of phenol in the laboratory-scale and pilot-scale WSP. The laboratory-scale WSP System I units, consisting of facultative pond l, facultative pond 2 and maturation pond in series, were fed with different influent phenol concent r ations of 300, 500, 600 and 700 mg/L, but the same organic loading rate of 1000 kg COD/(ha.d) to the facultati ve pond 1. System II consisting of facultative pond 2 and maturation pond in series were fed with t h e same waste as System I, but the organic loading rate of 250 l<g COD/(ha.d) was applied to the facultative pond 2. Data from this study showed that soluble chemical oxygen demand (SCOD) removal efficiencies in the WSP were found to decrease with increasing influent phenol concentrations. At influent phenol concentrations of 300, 500, 600 and 700 mg/L in the facultative pond 1 of System I and facultative pond 2 of System II, the SCOD removal efficiencies were 55, 40, 37 and 25 percent for the facultative pond 1 of System I, and 80, 63, 58 and 55 percent for the facultative pond 2 of System II, respectively. However in the facultative pond 2 and maturation pond of System I and in the maturation of System II, the SCOD removal efficiencies were not much affected by the influent phenol loadings. Chlorophyll g concentrations were found to decrease with increasing influent ph enol concentrations in the facultative pond 1 of System I and facultative pond 2 of System II. However, in the facu ltative pond 2 and maturation pond of System I and maturation pond of System II, the toxic effect of phenol was not much evident. Phenol shock loading of 500 mg/L, applied for one day to the pilot-scale WSP, chlorophyll .a resulted in the decrease of the pilot-scale facultative pond 1 unit while in the pilot-scale facultative pond 2 and maturation pond, the chlorophyll £!: was not a ffected much. Peak phenol concent1·ations in the pilot-scal e facultative pond 1 and facultative pond 2 appeared about one day after shocl< loading, being 47 and 16 mg/L. No phenol was found in the pilot-scale maturation pond effluent.