DISCUSSION

Mr E. A. Drew

Chief Engineer, Middle Lee Regional Drainage Scheme

The selection of the title of the Paper is propitious as it emphasizes advanced treatment rather than a tertiary treatment. The development of tertiary treatment processes has risen principally from the demand for a reduction in the suspended solids content in the effluent produced by secondary treatment. This implies that secondary treatment is inadequate and in many cases in practice this is true. However, a Royal Commission standard effluent can and should be consistently produced by all secondary processes. In case of a proven need to produce a better effluent having special characteristics then it is advanced treatment, in thefirst instance by an extension of the secondary treatment, rather than the introduction of tertiary treatment that achieves the required standard.