Water ecological restoration for sewage pond with high salinity in arid area:A case study of Alaer oxidation pond
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Abstract:
The restoration and polluted water resource utilization in arid regions is an important way to solve the shortage of regional water resources.The Xinjiang Uygur Autonomous Region is an inland arid zone and lacks water resources with a fragile ecological environment,and shows a prominent contradiction between water supply and demand.Over-exploitation of water resources and water pollution have exacerbated the contradiction between water supply and demand,resulting in the continuous deterioration of the water environment.Water pollution control is an emerging problem that needs to be solved urgently to favor Xinjiang′s economy and social development.This study took the project of Xinjiang′s Alaer sewage pit pond ecological restoration and landscape improvement as an example to explore key technologies for the process of ecological restoration of high-salt water bodies. A comprehensive treatment plan was formulated according to the regional environment and pollution characteristics of the oxidation pond.For this purpose,water safety,water environment,water resources,and water ecology was adopted.Innovations were made basis on the existing integrated technology of water quality enhanced purification and water ecological restoration.In addition to traditional sewage interception and water diversion projects,the application of modified mineral materials,targeted microbial agents and salt-tolerant plants simultaneously achieved water quality improvement and endogenous control.Specifically,it included 4 measures.(1) Source control and pollution interception:Prevented pollution sources from entering the oxidation pond;(2) Water quality improvement:Eliminated pollutants in water,achieved water quality standards,and restored water body functions;(3) Living water circulation:Improved the self-purification capacity of the oxidation pond and reduced water pollution,and improved the regional water circulation system;(4) Ecological restoration:Repaired and improved the regional water ecological environment and realized the comprehensive utilization of wastewater resources.From source blocking in the early stage,polluted water treatment in the middle-term to the long-term maintenance of the later restoration,and finally realized water quality purification and ecological system reconstruction in the Alaer oxidation pond. Before treatment,the total salt,chloride,chroma,and COD of the oxidation pond exceeded the national standards,which was inferior to category V waters.As the construction progressed,the chroma,COD,and ammonia nitrogen in the water bodies of the oxidation ponds showed a gradual decline and became stable day by day.After project implementation,the black and odor of the water body disappeared,the transparency increased from less than 30 cm to more than 80 cm,the chroma decreased from 20 times to 4~8 times,and the COD decreased from 96~148 mg/L to 37~50 mg/L,respectively.The growth rate of aquatic plants was accelerated,a large number of submerged plants could be observed in the pond,the singleness of the ecosystem was changed,and the selfpurification ability of water was enhanced.Within one month after the completion of construction,the water quality did not change much.Eight months later,COD and chroma had increased significantly,and the results of the changes were consistent.It was speculated that the corresponding pollutants were refractory organic dyes,and the modified zeolite was the main reason for their removal,a small amount of modified zeolite was needed to be sprayed for maintenance.Ammonia nitrogen and total nitrogen slightly increased,but the total phosphorus mass concentration continued to decrease after construction,indicating that the technical scheme proposed could effectively remove phosphorus from water and the results could be maintained for a long time. After the undergoing harmless treatment and ecological restoration,the water quality in the oxidation pond had been significantly improved.All indicators meet the requirements of the remediation goals,and all pollutants had a downward trend.The results showed that the application of modified mineral materials targeted microbial agents,and saline-tolerant aquatic plants synergistic technology treat Xinjiang cotton pulp and viscose fiber industry production wastewater,and could effectively reduce water pollutants,and improve the water quality.This research can provide reference for ecological restoration of high-salt wastewater in arid regions.
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