Modelling Nitrogen Transformation, Removal and Re-use of treated water in an Integrated Wastewater Treatment Plant (IWTP)

TARIMO, IRENE A. (2013) Modelling Nitrogen Transformation, Removal and Re-use of treated water in an Integrated Wastewater Treatment Plant (IWTP). Doctoral thesis, The Open University of Tanzania.

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Abstract

This study was carried out at Mabogini wastewater treatment system in Moshi, Kilimanjaro, Tanzania. The principal question was how to determine and model N-transformation, removal and re-use in IWTP to develop dynamic mathematical model, tool for environmental management. Grab wastewater samples were collected three times a week from March 2010 to February, 2011. Flow rate, Temp., pH, and DO were measured “in-situ” using HACH DR 2500 (2001). TSS, Turbidity, BOD5, NH3-N, TKN, Org-N, NO2-N, NO3-N, Chl”a”, N-Sediments, N-Planktons, N-Fish and F-Coliforms were measured in water quality Lab. using APHA, 2005 standards. Heavy metals Cd, Cr, Cu, Hg and Pb were analysed by AAS to evaluate toxicological effects in fish. Hypothesis 1, revealed mean of 3.3 mg/l NH3-N in Fish Pond higher than required 0.2 mg/l. Hypothesis 2 developed IWTP model with better correlation value (R2 ≈ 0.8) at 95% confidence level than single unit with (R2 ≈ 0.7). Routes of N-transformation were NH3-N uptake (57.19%) and nitrification (53.96%) while removal routes were Org-N accretion (85.24%) and denitrification (41.63%). N-transformed was 55.40%, while removed was 44.60%. Heavy metals results in fish muscles were higher than WHO (2006) & TBS (2005) standards in the brackets: Cd 1.81 (0.1), Cr 3.45 (1.0), Cu 4.25 (2.0), Hg 1.27 (0.01) and Pb 26.11 (0.1). Thus, fish were not suitable for human consumption. The IWTP model can answer problems of performance, productivity and pollution when forcing functions change. Follow up all projects in Tanzania & elsewhere that use IWTP. MUWSA construct additional HSSFCWs downstream WSPs 5 and 6 before release outlet to fish pond, farms and receiving water bodies. Water engineers, managers and policy makers use the developed IWTP model for decision-making in similar climatic regions.

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