Disposal of waste water is subject to regulation in many countries. Outlet control, for example, must be arranged so that the volume of waste water is continuously measured and recorded and an aliquot part, in proportion to the volume of the flow, is sampled. Figure 22.1 illustrates a system for measuring the flow in an open canal with a venture flume. For information about the venture flume and other measuring systems, please contact the municipal authorities dealing with sewage water treatment.

As to sampling, one example of the procedure is shown in figure 22.2.Signals indicating the volume of water measured in the flume are transmitted via a control unit to the sampling device. An aliquot volume of the flow is sampled whenever a predetermined volume of water (say 100 l) has passed the flow transmitter the daily samples are mixed, and after an optional period a smaller volume of the mixed samples is analyzed.