Abstract
Selection of appropriate river water treatment methods is important for the restoration of river ecosystems. An in-depth review of different river water treatment technologies has been carried out in this study. Among the physical-engineering processes, aeration is an effective, sustainable and popular technique which increases microbial activity and degrades organic pollutants. Other engineering techniques (water diversion, mechanical algae removal, hydraulic structures and dredging) are effective as well, but they are cost intensive and detrimental to river ecosystems. Riverbank filtration is a natural, slow and self-sustainable process which does not pose any adverse effects. Chemical treatments are criticised for their short-term solution, high cost and potential for secondary pollution. Ecological engineering-based techniques are preferable due to their high economic, environmental and ecological benefits, their ease of maintenance and the fact that they are free from secondary pollution. Constructed wetlands, microbial dosing, ecological floating beds and biofilms technologies are the most widely applicable ecological techniques, although some variabilities are observed in their performances. Constructed wetlands perform well under low hydraulic and pollutant loads. Sequential constructed wetland floating bed systems can overcome this limitation. Ecological floating beds are highly recommended for their low cost, high effectiveness and optimum plant growth facilities.
Highlights
Pollution of river water is one of the biggest environmental problems, in developing and underdeveloped countries
Ecological restoration of river ecosystems and treatment of river water can be successfully done by applying riparian wetlands, nitrogen (N) and phosphorus (P) sedimentation and absorption, aeration and ecological floating beds [10]
Sheng et al [47] used a hybrid process combining the biological, chemical and engineering processes to treat the highly polluted river water at the field level [48]. Their process significantly removed chemical oxygen demand (COD), biological oxygen demand (BOD) (>70%) and odour from the polluted river water. Aquatic plants such as Pontederia cordata demonstrated potential for treating river water polluted with N, P and organic chemicals, the engineering process of aeration enhanced the water treatment efficiency of this aquatic plant [49]
Summary
Pollution of river water is one of the biggest environmental problems, in developing and underdeveloped countries. River water pollution in some countries is so severe that it cannot be used at all. It causes the spread of water borne diseases in many developing countries, emits severe and intolerable odours and pollutes the air. Water quality management depends on the strict policy controls for discharge of solid waste, wastewater, stormwater and standards of treated or untreated wastewater, which requires cost and time for successful execution [1]. Water management plans must consider sustainable strategies and policies for the successful remediation of polluted water [2]
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