Why are biological methods usually not satisfactory for the disposal of industrial waste?
Several reasons. two important considerations are: 1) not all wastes are amenable to biological destruction (bioligical activity does nothing to the wastes); 2) The amount of space that needs to be given over to treatment and storage of waste is a function of the rate of treatment and rate of production of waste. Industrial activity produces large quantities of wastes over short time periods, generally speaking. If the treatment process is not fast, the industry will need to create a large volume of storage for that treatment, There is a residence time problem; you have a mass input and an equal mass output, and the amount of volume that must be given over for storage (residency) is the amount that will be produced during the time required for successful treatment. If the average flow through is faster than the average treatment time, the system will discharge partially untreated wastes. Biological treatment tends to be very slow, so you need a large storage capacity for the treatment
