Background of Mashhad Waste Water
 ● 1353: the primary studies of gathering, refining and repelling waste water
 ● 1354: changing the executive organization from maskan ministry to Power ministry and stopping the studies
 ● 1368: continuation of the studies by Power ministry and preparing the executive plan of Mashhad waste water
 ● 1372: ratification of the final study research of phase one and continuation of the second phase and starting executive operations

 In these studies, Mashhad was divided to two parts: east and west, and two refineries were considered for it: one in the west (Parkand Abad) and the other in the east (Olang). The final capacity of Parkand Abad refinery is 468000 cubic meters per day that this refinery is active with the nominal capacity of 15000 cubic meters per day.
 

Waste Water Refinery of The East (Olang):
This refinery in which the most of Mashhad’s waste water will be refined is located in the south of Kashaf Rood with the area of 600 hectares which is expandable to 900 hectares. Its distance from the city by the year 1400 is about 11 kilometers. Its average altitude from the surface of the sea is 890 meters.
 

   Refining Process in The First Execution:
In the first execution phase, the capacity of the refinery is about 25000 cubic meters per day and the refinery has 4 facultative (optional) pools with the capacity of 12,500 cubic meters per day and 2 reserve and puberty pools. The coming waste water, after passing through the garbage separation and measuring units enters the bee havazi digestion holes.
In each of the facultative pools there are two digestion holes that the coming waste water enters them through a pipe from underneath. The digestion pools are shaped like upside down pyramids with sloping side walls. And since the waste water current in these holes is from lower part towards upper parts, the more the waste water goes up the more it loses its speed. Losing speed causes the small and light germs to settle in the holes and in this way almost all the germs that can settle are settled. The duration of hydraulic stay in these holes is about 18 hours. The exiting waste water from the holes is added to the existing amount of water in the facultative pool. In the digestion holes there are absolute conditions of bee havazi. As the result of the coming of the oxygen to the water surface in facultative pool, a thin layer of water is saturated by oxygen and is exposed to a condition of havazi. Gradually, in the lower layers, the amount of the penetration of oxygen and the viscosity of the dissolved oxygen in the water reduces and near the bottom of the pool there is an absolute condition of bee havazi. The duration of the hydraulic stay in facultative pools is about 16 days. The waste water is transferred to reserve and puberty pools through exiting overspills. The duration of the hydraulic stay in reserve and puberty pools is about 5 days. During this period almost more than 99% of the diseases causing micro-organisms are destroyed and there is no need to add chlorine to the exiting waste water.

   Using The Refined Waste Water :
There are considered for each reserve pool an exiting overspill and a siphon overspill. The over spilled water from the exiting overspills is emptied in Kashaf Rood. The exiting water from the siphon overspill are transferred to the refinery fields considered for planting trees and its extra is emptied in Kashaf Rood. The water of this river is used in the lower part fields for agriculture.