One of the basic bacteriological findings used in helping to determine the quality and safeness of drinking water is the agar plate count. Raw water samples show the kind of water entering the plant and are a fair indicator of the treatment that will be needed. Plate counts of water samples taken at various places in the plant, such as settling basins or point of chlorination, show the effectiveness of the various treatment. Water leaving the plant is termed plant effluent, and results on this water are of primary concern. Its count should be very low, such as 1-8 per mil, if the water has been successfully treated.