title: A promising approach of reject water treatment using a tidal flow constructed wetland system employing alum sludge as main substrate.
abstract: This study examined a novel reuse of alum sludge, an inescapable by-product of drinking water treatment process when aluminium salt is added as a coagulant, as the main medium in a laboratory-scale multi-stage constructed wetland (CW) system for reject water treatment. Such reject water is a main concern in municipal wastewater treatment plant (MWWTP) for increasing the organic and nutrient loading. A 'tidal flow' strategy was employed to enhance the wetland aeration to stimulate organic matters (OM) and ammoniacal-nitrogen (N) oxidation while the 'step feed' operation was adopted to supply the necessary amount of carbon source for denitrification. The results reveal that alum sludge acting as P adsorbent can secure the P removal. Meanwhile, high removals of N and OM can also be obtained due to the active bacteria growth on the alum sludge surface. The results show that average removal efficiencies of 65.4 +/- 12.3% for chemical oxygen demand (COD), 67.8 +/- 9.2% for five-day biochemical oxygen demand (BOD5), 33.6 +/- 17.0% for N and 99.5 +/- 0.49% for P can be achieved over a period of 190 days. This indicates that novel reuse of alum sludge as medium in CW system can provide a promising approach for reject water treatment. Therefore, it will significantly reduce the amount of pollutant feedback through reject water recycling in a MWWTP.
authors: School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China. yangyongzhe@xauat.edu.cn
authors: Y
authors: Y
authors: Yang
authors: Y Q
authors: YQ
authors: Zhao
authors: S P
authors: SP
authors: Wang
authors: X C
authors: XC
authors: Guo
authors: Y X
authors: YX
authors: Ren
authors: L
authors: L
authors: Wang
authors: X C
authors: XC
authors: Wang
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D007220:Industrial Waste; D009930:Organic Chemicals / Q000302:isolation & purification; D010758:Phosphorus / Q000302:isolation & purification; D000644:Quaternary Ammonium Compounds / Q000302:isolation & purification; D014872:Water Movements; D018508:Water Purification; D053833:Wetlands
chemical_list: D017607:Aluminum Compounds; D007220:Industrial Waste; D009930:Organic Chemicals; D000644:Quaternary Ammonium Compounds; D010758:Phosphorus