In situ sediment treatment in Kai Tak Nullah Approach Channel to control odours and methane gas production

The sediments in Kai Tak Nullah Approach Channel (KTN) are responsible for the sulphide odour that is characteristic of the area around Kai Tak Airport. A method of controlling these sulphide odours by nitrate addition directly to the sediments was tested in the laboratory and an area of the KTN. Nitrate addition was found to increase sediment redox, oxidise the sulphides to sulphates, increase the rate of bacterial breakdown of organic materials, and reduce acute sediment toxicity. The laboratory and field tests of the treatments showed that nitrate addition could effectively control odours by oxidising the sulphides present and prevent future odour generation by providing an better and more efficient electron acceptor than is currently available for organic degradation. Nitrate addition will reduce or minimise future methane gas generation by increasing the degradation rate of the organic material accumulated at the bottom of KTN.