Using aerated gravel-packed contact bed and constructed wetland system for polluted river water purification: A case study in Taiwan
Journal
Journal of Hydrology
Journal Volume
525
Pages
400-408
Date Issued
2015
Author(s)
Abstract
The Ju-Liao Stream is one of the most contaminated streams in Kaohsiung City, Taiwan. A constructed wetland (CW) system was built in 2010 for polluted stream water purification and ecosystem improvement. An aerated gravel-packed contact bed (CB) system was built in 2011 and part of the stream water was treated by the CB before discharging to the CW. The influent rates of the CW and CB were approximately 5570 and 900 m3/d, respectively. The CW contained one free-water surface basin planted with emergent wetland plants, followed by the plug-flow channel-shaped free-water surface basin planted with emergent and floating wetland plants. The mean measured hydraulic loading rate (HLR), hydraulic retention time (HRT), water depth, and total volume of wetland system were 1.7 m/d, 0.68d, 0.7m, and 4400m3, respectively. The aeration zone of the CB system had a dimension of 24m (L)×8m (W)×3m (H), which was filled with gravels (average diameter=5cm) with a porosity of 0.4, and the aeration rate was 7.8 m3/min. Results show that the CB system was able to remove 69% of suspended solid (SS), 86% of biochemical oxygen demand (BOD), and 58% of total nitrogen (TN). Up to 82% of BOD and 27% of TN could be removed in the CW system. Removal efficiency of SS was affected by the growth of chlorophyll a in the CW system due to the growth of algae. The observed first-order decay rates (k) for BOD and TN in CB were 9.3 and 4.21/d, and the k values for BOD and TN removal in CW were 2.5 and 0.451/d. The high pollutant removal efficiencies in the CB system indicate that the system could enhance the organic and nutrient removal through the biological processes effectively. Sediments contained high total organic matter (1.9-4.5%), sediment total nitrogen (6.4-10.1 g/kg), sediment total phosphorus (0.59-0.94 g/kg), and sediment oxygen demand (0.9-4.1 g O2/m2d). The organic and nutrient-abundant sediments resulted in reduced conditions (oxidation-reduction potential measurements <158 mV). Increased evenness, richness, and biodiversity for birds and amphibious animals reveal that the CW had a positive impact on the ecosystem conservation and wildlife habitat rehabilitation. © 2015 Elsevier B.V.
Subjects
Aerated gravel-packed contact bed; Constructed wetland; River pollution; Water quality; Wetland hydrology
Other Subjects
Animals; Biochemical oxygen demand; Biodiversity; Channel flow; Decay (organic); Ecology; Ecosystems; Gravel; Hydrology; Loading; Nitrogen; Nutrients; Oxygen; Pollution; Purification; Redox reactions; Removal; Rivers; Sediments; Water pollution; Water quality; Water resources; Water treatment; Water treatment plants; Wetlands; Aerated gravel-packed contact bed; Biochemical oxygen demands (BOD); Constructed wetlands; Hydraulic retention time; Organic and nutrient removals; Oxidation reduction potential; Pollutant removal efficiency; Wetland hydrology; River pollution; aeration; constructed wetland; habitat conservation; purification; river bed; river pollution; urban pollution; Kaohsiung; Taiwan; Taiwan; algae; Animalia; Aves
Type
journal article