Abstract
The performance and hydraulic characteristics of rock bed contact-purification of eutrophic coastal water were investigated in pilot-scale channels to determine the design and operating parameters (medium size, channel length, flow rate) for optimum rock-bed channel operation.
The results are summarized as follows :
1) 60-80% of SS and 8-17% of T-TOC in coastal water were removed after hydraulic retention time of 1-5 hrs.
2) The channels packed with rocks under 80mm were clogged by shellfish (Mytilus edulis etc) attachment in the short term. It is practical to use larger rocks (over 100-150mm) in order to prevent clogging and provide sufficient stability of contact-purification in the long term.
3) Detachment of biofilm was observed in the channels of high hydraulic loading and/or small rocks.
4) High deposit ratio was observed on the downstream area in the channel of high hydraulic loading. Detachment of biofilm significantly reduced the efficient purification length in channels, and moved the area downward.
5) The low loading treatment was expected to allow long-term purification without the rapid development of clogging.
