טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLevi Nimrod
SubjectComparative study of synthetic and tuff substrates in
saturated aerobic biofilm reactors for the
treatment of olive mill wastewater
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Emeritus Michal Green
Professor Michael Iggy Litaor
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

A system was developed which combines coagulation-flocculating to reduce the TSS, anaerobic treatment to reduce the COD and aerobic treatment for the final polishing. This system is designed to treat agro-industrial wastewater rich in organic matter, especially OMW. This system is called -

"MISSTOW" - Mobile Integrated Sustainable System for Treatment of Organic Wastewater. The first two modules of MISSTOW reduce approximately 84% of the COD and 76% polyphenols from the OMW, while the legal release of wastewater to the WWTP is 2,000 and 100 ppm of COD and polyphenols, respectively. This study examines the last module of the MISSTOW system, the aerobic polishing which consists of a series of saturated aerobic Biofilm cells (BAC). The study conducted a comparison between different substrates in the cells, a lightweight synthetic carrier manufactured by AqWise LTD and a natural substrate of tuff with varies grain size. The study examines two hydraulic retention times (HRT) with an aerial organic load of 66-1,677 g*day-1*m-2 and volumetric organic load ranging from 42 - 1,062  g*day-1*m-3. The BAC with tuff bed showed a reduction of 86% of COD during HRT of 7 days, and 84% reduction of COD in the light carriers, using HRT of 8.7 days. A 64% and 68% reduction of polyphenols in the tuff and light carrier beds respectively was noted. OMW's are characterized by a low ratio of COD: N, while the ratio in the BAC bulk liquid was 140: 1, respectively. Therefore, we examined the effect of additional nitrogen in the last two cells in one of the tuff systems, while the second served as a control. The results show an improvement of approximately 11% in the removal of the COD. No significant improvement was found in the removal of polyphenols compounds as a result of the addition of nitrogen. To further evaluate the potential degradability of the non-biodegradable residue, the HRT was extended in the BAC to -16 days. It was found that even after a long period of time 1,200 ppm of COD still remained in the treated OMW with a very slow biological degradation rate. Two methods of periodic cleaning of BAC were examined in the tuff bed, in order to overcome the clogging originating mainly from the development of biofilm. The first method made use of hydrogen peroxide to oxidize the organic matter while the second procedure called for drying the bed for about 66 days. Cell's hydraulic conductivity (Ks) was used to estimate the treatment success. improvement in Ks was measured in all the cells in both treatments and they were quite similar to the Ks of cells before the experiment. In the light carriers system a method was developed together with AqWise to unclog the bed. This method failed to bring the Ks to the initial status. MISSTOW system treated 113 m3 of OMW. The system successfully met the standard in respect to TSS, TP and TN values, and managed to produce results close to the Israeli standard with regard to COD and polyphenols.