Design of water hyacinth ponds for removing algal particles from waste stabilization ponds.

In this study it was demonstrated that when water hyacinth ponds (WHPs) are used for polishing the effluent from waste stabilization ponds (WSPs), suspended solids (mostly algal particles) are efficiently separated, which also resulted in the reduction of insoluble forms of COD and nutrients. The high pH of the WSPs effluent was easily adjusted to 6-7 as it passed through the WHPs. However, the use of water hyacinth rapidly reduced dissolved oxygen at the first cell to less than three mg/L or very frequently to a level of anaerobic state. Reduction of suspended solids at the WHPs mainly depends on the detention time and pH. An empirical separation model incorporating the detention time and pH dependence was developed.

Control and separation of algae particles from WSP effluent by using floating aquatic plant root mats.

In this paper, the potential uses of water hyacinth and its root mats for separating algae particles in the effluent from waste stabilization ponds (WSPs) were discussed. Pilot-scale integrated processes consisting of WSPs and multiple WHPs (water hyacinth ponds) were operated in order to extract effects of the root mats on the reduction of algae concentrations. Root mats in the bottom of WHPs separated significant amount of the algae cells through attachment as the effluent from WSPs passed through them. Attachment of the algae particles to the surface of live roots was found to be similar to adsorption phenomena but it lasted even at saturation, probably due to the continuous reproduction of active attachment sites by detachment and growth of the roots. Additionally, this paper discusses attachment mechanisms and other issues concerning design and polishing of the WSPs effluent by WHPs.