Now showing 1 - 2 of 2
  • Publication
    A promising approach of reject water treatment using a tidal flow constructed wetland system employing alum sludge as main substrate
    This study examined a novel reuse of the alum sludge, an inescapable by-product of the production of drinking water 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 pollutants and 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 acted as P adsorbent can secure the P removal. Meanwhile, high removals of ammoniacal-nitrogen and organic matters can also be obtained due to the active bacteria attached growth on the alum sludge surface. The results show that average removal efficiencies of 65.4 ± 12.3% for COD, 67.8 ± 9.2% for 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 pollutants feedback through reject water recycling in a MWWTP.
      1793Scopus© Citations 28
  • Publication
    Towards the development of a novel construction solid waste (CSW) based constructed wetland system for tertiary treatment of secondary sewage effluents
    This study was conducted to examine the possibility of using construction solid waste (CSW), an inevitable by-product of the construction and demolition process, as the main substrate in a laboratory scale multi-stage constructed wetland system (CWs) to improve phosphorus (P) removal from secondary sewage effluent. A tidal-flow operation strategy was employed to enhance the wetland aeration. This will stimulate aerobic biological processes and benefit the organic pollutants decomposition and nitrification process for ammoniacal-nitrogen (NH4+-N) removal. The results showed that the average P concentration in the secondary sewage effluent was reduced from 1.90 mg-P/L to 0.04 mg-P/L. CSW presents excellent P removal performance. The average NH4+-N concentration was reduced from 9.94 mg-N/L to 1.0 mg-N/L through nitrification in the system. The concentration of resultant nitrite and nitrate in the effluent of the CSW based CWs ranged from 0.1 to 2.4 mg-N/L and 0.01 to 0.8 mg-N/L, respectively. The outcome of this study has shown that CSW can be successfully used to act as main substrate in CWs. The application of CSW based CWs on improving N and P removals from secondary sewage effluent presents a win-win scenario. Such the reuse of CSW will benefit both the CSW disposal and nutrient control from wastewater. More significantly, such the application can transfer the CSW from a ‘waste’ to ‘useful’ material and can ease the pressure of construction waste solid management. Meanwhile, the final effluent from the CSW-based CWs can be used as non-potable water source in landscape irrigation, agriculture and industrial process.
      836Scopus© Citations 6