The purification of sewage with the aid of ponds containing bulrushes or reeds in the Netherlands

The work of Seidel showed the possibility of sewage treatment with ponds in which swamp plants were grown. Especially bulrush, Scirpus lacustris, was said to possess high waste water purifying qualities. Based on this information it was decided to start in 1967 an experiment with the treatment of the sewage of a camping site with a bulrush pond. In this pond the sewage was, when necessary in order to maintain a constant water depth diluted with water supplied from a neighbouring lake. In 1969 an additional number of experimentaal ditches for sewage treatment were made to enable a comparison of the properties of bulrushes and reeds (Phragmites australis) in purifying sewage. In these ditches presettled sewage was treated. Here also supply water was added. From this comparison and laboratory research, conclusions with respect to the purification process could have been drawn. Also the groundwater below the ponds has been investigated to show whether any pollution occurs and finally attention has been paid to the influence of a dry period during autumn on the nitrogen removal from the pond bottom.