Question

Which one is not a type of Equalization tanks?

(a) Flow through type

(b) Intermittent flow type

(c) Variable inflow/constant discharge type

(d) Intercept type

The question was posed to me in unit test.

The origin of the question is Principle for the Preparation of Water Supply in portion Valuation, Reports Technical and Design Data of Civil Engineering Drawing

Answer 1

Right choice is (d) Intercept type

Best explanation: The simple flow through type equalization tank is mainly useful in assisting self neutralization or evening out of fluctuating concentrations, not for balancing of flows since a flow through type tank once filled, gives output equal to input.

Flow balancing and self-neutralization are both achieved by using two tanks, intermittently one after another. One tank is allowed to fill up after which it is checked for pH (or any other parameter) and then allowed to empty out. The second tank goes through a similar routine. Intermittent flow type tanks are economic for small flows from industries.

When flows are large an equalization tank of such a size may have to be provided that inflow can be variable while outflow is at a constant rate, generally by a pump.The capacity required is determined from a plot of the cumulative inflow and a plot of the constant rate outflow and measuring the gaps between the two plots. A factor of safety may be applied if desired.