טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentEfman Irina
SubjectElectrocoagulation as a Part of Greywater Treatment and
Reuse
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Eran Friedler
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Substitution of drinking water with service water or with alternative source of water (greywater) used for non-potable uses helps supporting the sustainability of water use in the urban sector.

The main goal of the research was to study electrocoagulation as on-site pre- or post-greywater treatment process. Two types of greywater (GW) were used: greywater from an office building (Rabin building) consisting of GW from washbasins in washrooms, and mixed domestic greywater (shower and washbasins) Student's Dormitory. The quality of both types of greywater was highly variable.

In the first step, Coagulation-flocculation (CF) experiments were performed in order to find optimal doses, based on pollutants removal efficiency and coagulant's dosing. Ferric chloride and Alum as a coagulants were examined. Average optimal doses of FeCl3 and Alum for treatment of GW from Rabin building and Student Dorm's were: 10 and 30 mg/l FeCl3-Fe and about 3 mg/l Al.

In the next stage of the research, synthetic greywater with constant chemical composition was used. The purpose was to understand the factors affecting the electrocoagulation (ElC). The influences of initial pH and electrical currents on the effectiveness of the process were studied. Two types of anodes (Al and Fe) were examined. It was found that ElC with iron anode is not efficient in low current intensities and low pH values. The efficiency of the process with Fe anode is dependent on the oxidation rate of Fe2+ released from the anode to the solution to Fe3+ ions.

From the batch experiments with "real" greywater was found that pollutants examined (apart from turbidity) were removed more efficiently by ElC.

In the last stage continuous ElC experiments with Iron anode and Stainless-steel cathode were performed. Optimal average Iron dose for greywater from Rabin building was 80 mg/l, and for Dormitory Building - 109 mg/l. Analysis of particle size distribution before and after ElC exhibited significant variation for the two types of greywater. In the raw greywater from Rabin building the majority of particles lied in the range of 100-180µm. The range of the particle size of raw greywater from the Dorm. Building was much wider (0.375-1,104 µm). Particle size distribution in the treated greywater shifted to the direction of smaller particles since the larger ones were removed.