Roles of water hyacinths and their roots for reducing algal concentration in the effluent from waste stabilization ponds

This paper deals with use of water hyacinth and its root mats for controlling algal concentrations in the effluent from waste stabilization ponds (WSPs). Pilot-scale integrated processes coupled WSPs with multiple WHPs (water hyacinth ponds) were operated in order to determine the effects of the plant and root mats on reduction of algal concentrations on a quantitative basis. As flows from WSPs passed through the WHPs, root mats in the bottom as well as leaves and stems on the water surface of WHPs separated and controlled significant amount of algal cells by various mechanisms such as attachment, settling, respiration and suppression of algal growth. Attachment of algal particles to the plant roots was very similar to adsorption processes; i.e. there is a maximum capacity in a given weight of roots. However, effluent algal concentrations did not increase at saturation probably because of the sloughing-off of attached particles as a clump from the roots and generation of new attachment sites due to the growth of roots. Additionally, this paper discusses attachment forces and other issues concerning polishing of the WSPs effluent by WHPs.