|M.Sc Thesis||Department of Civil and Environmental Engineering|
|Supervisors:||Assoc. Prof. Armon Robert|
|Prof. Gidon Oron|
The shortage of water is growing continuously and one of the solutions is the treatment of the effluent from municipal wastewater treatment plants and its utilization for irrigation. The main drawbacks of conventional effluent reuse are the low microbiology and chemical quality, and an increase in the salinity, which causes damage to the soil, crops' yields and underground water quality. In certain areas in Israel there are stiff requirements of BOD<5 ppm & TSS <5 ppm. These quality demands can be met by means of membrane technology, the most promising being micro-filtration and ultra-filtration. The main limitation in membrane treatment of the effluent is the decrease of the flux, as a result of fouling processes.
The main purpose of this work is to offer extra pretreatment for the upgrading of waste stabilization ponds' effluent for unlimited irrigation. Pretreatment by flocculation and granular filtration can be a suitable complementary stage to the biological treatment. The results showed that the influence of the suspended solids content (expressed by the turbidity) on the stability of the flow is low, while the initial UF flux had a larger influence on the UF permeate flow stability. An additional result is that the use Alum as a coagulant is likely to create inorganic fouling on the UF membrane surface.
From these above results it is possible to conclude that it is not necessary to use a high dosage of alum. A low dosage of alum is enough to reduce the turbidity to the range of 20-40 NTU. Adding alum can yield lower turbidity but might cause excess of aluminum in the water. In addition, an economic analysis was carried out, examining different operational options to improve the effluent. In comparing the costs it was found that it is preferable to perform around 8 Cleaning In Place (CIPs') per day and not to use flocculants. However, the multiple pauses of the UF system operation for cleaning is likely to cause an increased amortization of the mechanized equipment and lack of process stability.
The results from this work show that it is possible to upgrade the effluent of waste stabilization ponds for unlimited irrigation to the high quality of 5/5 (BOD/TSS) and less than 10 Fecal Coliform /100 ml at a reasonable cost of about 0.6 - 0.7 NIS/m3.