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| Pretreating swine wastewater using ecological primary enhanced flocculation |
| Received:November 15, 2021 |
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| KeyWord:swine wastewater;ecological flocculant;vermiculite flocculant;primary enhanced pretreatment |
| Author Name | Affiliation | E-mail | | WANG Li | College of Marine and Environmental Sciences, Tianjin University of Science & Technology, Tianjin 300457, China | | | CHEN Guanyi | College of Marine and Environmental Sciences, Tianjin University of Science & Technology, Tianjin 300457, China | | | HAO Linlin | College of Marine and Environmental Sciences, Tianjin University of Science & Technology, Tianjin 300457, China | | | SHAO Weimin | College of Marine and Environmental Sciences, Tianjin University of Science & Technology, Tianjin 300457, China | | | ZENG Ming | College of Marine and Environmental Sciences, Tianjin University of Science & Technology, Tianjin 300457, China | | | WANG Chang | College of Marine and Environmental Sciences, Tianjin University of Science & Technology, Tianjin 300457, China | wangc88@163.com |
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| Abstract: |
| Owing to the high concentration of pollutions in swine wastewater produced via dry-wet separation, the current volume of discharge is difficult to process with biochemical treatments. Therefore, primary enhanced flocculation pretreatments were conducted using both vermiculite as an ecological, non-toxic inorganic mineral flocculant and the conventional cationic coagulant C-PAM. This procedure aimed to reduce the load of subsequent biochemical treatments. The isolated effect of vermiculite flocculant alone and the synergistic effect of vermiculite flocculant combined with the coagulant C-PAM were investigated; changes in turbidity, COD, SS, ammonia nitrogen, total phosphorus, sedimentation velocity, and floc volume were analyzed after the flocculation pretreatment. Results showed that vermiculite had a good flocculation effect on swine wastewater. When the dosage of vermiculite flocculant alone was 8 g·L-1, the turbidity, COD, SS, total phosphorus and ammonia nitrogen of the swine wastewater were reduced from 405 NTU, 1 340 mg·L-1, 260 mg·L-1, 38.2 mg·L-1, and 296.4 mg · L-1 to 73.4 NTU, 611.7 mg · L-1, 60 mg · L-1, 2.5 mg · L-1 and 284.4 mg · L-1, respectively. Their removal efficiencies in wastewater reached 81.9%, 54.4%, 76.9%, 93.3%, and 4.1%, respectively, which greatly reduced the load for subsequent biochemical treatment. After primary pretreatment with 4 g · L-1 of a vermiculite flocculant and 24 mg · L-1 of C-PAM. Then the synergistic effect was studied, and turbidity, COD, SS, total phosphorus and ammonia nitrogen in the swine wastewater were 19.2 NTU, 454.5 mg·L-1, 34 mg·L-1, 5.5 mg·L-1, and 267.1 mg · L-1, respectively, with removal efficiencies of 95.3%, 66.1%, 86.9%, 85.5%, and 9.9%, respectively. These values were better than those of the vermiculite flocculant alone; compared with the latter, the removal rate via the synergetic treatment increased by 24.6%, 19.2%, 26.9%, 8.0%, and 6.2%. This indicated that the addition of C-PAM could help to remove pollutants and result in a good synergistic effect as it not only reduced the amount of vermiculite flocculant needed but also could be used as a raw material for composting with pig manure. Compared with the flocculation effect of traditional inorganic compounds, the load of the subsequent biochemical treatment was reduced effectively. The heavy metal concentration of the supernatant and flocculated sediment meet emissions and agricultural fertilizer standards. Additionally, the synergistic effect of vermiculite flocculant and C-PAM meant that the floc settling speed in the sediment flocculant PAC was faster and the volume was smaller. Therefore, ecological primary enhanced flocculation pretreatment will become an important method for the harmless and resourceful treatment of swine wastewater in the future. |
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