Abstract：In order to recover phosphorus and water resources from municipal sewage and reduce the reactor volume for subsequent treatment, forward osmosis membrane was used to concentrate municipal sewage. The effect of different initial pH on municipal sewage concentration and phosphorus recovery was explored. When forward osmosis concentration test was carried out with synthetic sewage, as the initial pH of feed solution (FS) was raised to 9.5 and the volume of FS was concentrated to 1/10 of the initial, the adsorbed phosphorus on the membrane and the spacer was about 44% of the initial total, which was conductive to phosphorus recovery. When FS was real municipal sewage and the initial pH of it was 9.5, there were agglomerated spherical particles on the fouled membrane surface, making the membrane surface pollutants more easily cleaned under this condition, and the water flux of membrane after cleaning was higher than that under the unadjusted pH conditions. After in-situ ultrasonic cleaning, the concentrated sewage became a suspension solution. The main components of the collected precipitate were CaCO3, struvite and magnesium phosphate. When initial pH was 9.5, the contents of CaCO3 and struvite in the resulting precipitate was higher than that under the other operating conditions. After adjusting the initial pH of the municipal sewage to 9.5 and concentrating it for three consecutive runs of 42 hours, the volume of the sewage was concentrated to about 8 times of the original volume, and the phosphorus recovery reached 63.9%. After the concentration is completed, the membrane was firstly subjected to in-situ ultrasonic cleaning, and then to chemical cleaning with alkali washing and acid washing. After cleaning, the water flux was about 78% of the initial membrane flux; the pH of the concentrated sewage was between 8.5~9.1; the COD/TN value was significantly increased from 3.6 to 11.5, which was conducive to the subsequent nitrogen and phosphorus removal process.
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WANG Mei-ling, WANG Ce, LI Yong-mei. Effects of the initial pH on the process of forward osmosis for concentration of municipal sewage and phosphorus recovery. CHINA ENVIRONMENTAL SCIENCECE, 2021, 41(2): 660-668.
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