Oxidation Ditches or Pasveer Ditches

This method of treating sewage was developed by Dr. Pasveer In Netherlands by treating raw  sewage from small communities. No primary treatment is required here. and thus there is no problem for digestive and disposing of  the settled primary sludge.

In essence, this method consists of an extended aeration type of activated sludge process, in which mechanical system of aeration is used. Also in construction, an oxidation ditch is like an oxidation pond provided with a rotor. The performance of an oxidation ditch it, however, better than that of an oxidation pond in the sense that is requires only about one-fifth of the land area that is required for an oxidation pond. It is a simple, cheap, and an efficient method for disposing of smaller quantities of waste waters.

The process involves a single unit treatment in an endless linedsor unlined channel, equipped with a special type of rotor which serve the purpose of agitating and circulating the sewage, and, thereby oxygenating the same. The rotor, not only gives oxygen supply of the sewage, but also helps in keeping the sewage solids in suspension, so as to act as the carriers of aerobic bacteria, by imparting sewage a velocity of more than 0.3 m/sec. The aerated sewage is then settled in settling tanks by stopping the rotor for about 2 hours, and then taking out the clear supernatant liquor at the time of no flow (i.e. during night hours in case of small communities) The excess settled sludge is well stabilized due to long detention periods. and can be easily dried on sand beds. and disposed of suitably.