Factors which facilitate waste water treatment by aquatic weeds – the mechanism of the weeds’ purifying action

Aquatic weeds such as water hyacinth, salvinia, pistia, and lemna have proved to be powerful bioagents which significantly purify wastewater lying under them. Even the performance of conventional oxidation ponds can be greatly enhanced by the simple expedient of introducing one of these aquatic weeds. Weeds absorb certain pollutants. But the contribution of absorption to the overall treatment is only one among several contributory factors. This paper examines the factors responsible for the water‐purifying ability of the weeds.