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Abstract

ABSTRACT
Dairy liquid wastes contributes considerably in the pollution of the Tigris within Mosul city particularly when suspended solids and oil pollution are concerned. Dissolved air flotation( DAF) is introduced to tackle the discharges arise from this industry. A pilot plant is constructed for this purpose. The pilot plant is subjected to variety of operating conditions of detention time ( 6-24 minutes), recycle ratio (25-100 %), pressure(40-70 psi) and air /solids ( A/S) ratio. The results revealed that the optimum values for detention time, recycle ratio, and pressure were 18 minutes, 100% and 60 psi respectively. A statistical treatment for the obtained results to relate all the studied factors is made in order to establish the best relation that gives the best results. The percent removal of suspended solids in the dairy discharges amounted to 80 % while that of oil amounted to 86%. This highly indicates the importance of introducing this physical unit among conventional wastewater treatment units. It is concluded that DAF has many merits represented by ease of operation, considerable reduction of pollutants which may be reflected on subsequent units. Due to short detention time, this unit becomes small and adds to the economy of the treatment.