Industrial Waste Monitoring: A Statistical Approach

Computation of correct user charges for large industrial customers requires a monitoring program to establish and detect significant changes in each industry's waste characteristics. The approach incorporates a model for selecting reasonable sampling intervals and a statistical control chart for detecting shifts in an industry's waste characteristics from prescribed mean values. The sampling interval model accounts quantitatively for a number of pertinent variables that affect the cost and utility of the monitoring program, including the costs of sampling and analysis, the probability of drawing erroneous conclusions from the data, and the time required to detect a significant shift in wastewater characteristics. The statistical control procedure adopted to detect shifts in waste characteristics is the cusum control chart.