r Alizadeh - Faculty of Engineering, Qom University of Technology,Qom,Iran
G Badalians Gholikandi - Faculty of Engineering, Qom University of Technology,Qom,Iran

In this study, the effect of instrumental methods, natural polymers(Carboxy methyl cellulose, chitosan, sodium alginate, etc.), chemical coagulants (aluminum sulfate, iron(III) sulfate, iron (III) chloride, etc.) and the composition of these materials on the dewatering of municipal sewage sludge has been investigated to determine the time of filtration and measure the moisture content of the resulting sludge cake to measure the dewatering ability of the sludge. According to the results of previous research, among chemical coagulants Iron (III) chloride was the best coagulant for aerobic digested sludge and the results showed that the sludge dewatering rate increased by ۸۰% compared to the control sample. (However ,in the case of modified materials, dolomite and bentonite are more efficient in dewatering sludge).Among natural polymers chitosan with the least amount of consumption compared to other coagulants, the rate of dewatering of digested sludge increases by ۶۱% and the amount of sludge moisture decreases by ۱۳% compared to the control sample.. Also in the section of common methods, ۱۰ process: filter press, belt filter press, screw filter, centrifuge, vacuum filter, thermal dryer, two-stage digester, Lime, sand bed and lagoon are investigated Has been. These options were compared from four aspects: technical, economic, environmental and managerial. accordingly, pressure filters, thermal dryers, lime, bed, lagoon and centrifuges are in the first to sixth priorities (Tsiporkova, E.et al.,۲۰۰۶). This paper reviews the difficulties in assessing sludge dewatering performance, and the main techniques used to evaluate dewatering performance are compared and discussed in detail. (Vu hien phoungto.et al.,۲۰۱۶). Although during recent years, improvements are realised in the field of dewatering, the actual dry solids content after dewatering remains at a maximum value of about ۳۵%. Aim: Need to find appropriate and practical methods with low cost and easy operation in dewatering from the biological sludge Sewage. Method: systematically all conventional, advanced and modern methods used in this field are examined, evaluated and compared in separate sections and the advantages and disadvantages of each are listed. at the end of each section, conclusions are given from the methods of that section. Results: The conclusions show the appropriateness of using modified natural mineral materials in this field.

dewatering, chemical coagulants, dewater ability, filter ability, sludge dewatering, sludge cake humidity