טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentRacheli Barak
SubjectBiological Treatment of Wastewater by Suspended Biosolids
Enhanced by Clay
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Armon Robert
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract


Domestic wastewater is based on several processes: physical, chemical and biological. Biological process, which is the main treatment, is mainly based on bacterial suspended growth that utilizes soluble organics, called activated sludge. In the case of olive mill wastewater (OMW) its treatment presents a serious environmental problem due to its recalcitrant biodegradation. The main problem with activated sludge process is effective flocculation and precipitation, expressed by the following value: sludge volume index (SVI). Commonly, activated charcoal addition is the main remediation step to improve SVI, however powdered clay has been reported to improve problematic SVI.

The main goal of the present research was to examine clay addition effect on bioflocculation process in conventional activated sludge, (solely and combined with 3% OMW). Following clay addition, effluents quality was monitored through the following parameters: TSS (total suspended solids: total, volatile and constant), TOC (total dissolved organic carbon), TN (total nitrogen), optical density (405nm), UV absorption, and pH.

The clay types tested were Montmorillonite and Kaolin (three types) at various concentrations (0-4000 mg/L). Montmorillonite has been found to be in effective in sludge settling at all concentrations. However, the three Kaolin types did improved sludge settling by 40%.

In comparison,  mixture of  municipal wastewater with OMW (3% v/v)  has been found to have lower pH, poorer settling capability, increased dissolved organic matter and higher optical density (405nm) than regular municipal wastewater.

Addition of superflocculant (C444) at concentration of 0.4 mg/L reduced the optical density (405nm) by 60%.

The improvement of activated sludge settling due to Kaolin  addition (2000 mg/L) of was independent of time (at time intervals from half to 6 hours).

Clay addition did not affect  UV absorption, total dissolved carbon concentration, total nitrogen concentration and pH significantly.

Our results show that adding minerals to the process improve the bioflocculation process and thus improve the settling process. Thus adding minerals to a municipal wastewater and a mixture of 3% OMW and 97% municipal wastewater can be treated such that the sludge and the treatment facilities are not damaged by the process.