The dissolved concentration of ozone used in the treatability
study = 2 mg/L.
We have to continuously maintain similar concentration in the
plant reactor of 13,000 L capacity. Hence the amount of dissolved
ozone needed = 13000 * 2 = 26 g.
This is the amount of ozone needed during start up. Once the
dissolved concentration reaches a steady state of 2 mg/L, the demand
for dissolved ozone is only for 1000 L/min waste water.
Hence, at steady state, the demand for ozone = 2000 mg/
min = 6.3648 lb/day. The solubility coefficient of ozone at 20 C is
0.31 mg/L in water per 1 mg/L in gas [39].
Hence, to obtain a dissolved concentration of 2 mg/L in the reactor,
the concentration of ozone required in the ozone/air mixture at
20 C = 2/0.31 = 6.45 mg/L. From the quotation received from a
leading Ozone Generator manufacturer (Spartan Environmental
Technologies, L.L.C. Mentor, OH 44060, USA), the capacity of ozone
generator was 7.5 lb/day. The concentration of ozone in the ozone–
air mixture was 5% by weight. This comes out to be 70 mg/L ozone
in the ozone–air mixture. Thus one unit of ozone generator is suf-
ficient to meet our ozone demand in this case. The quoted cost of
this device is 34000 USD. Since it was assumed that ozone generator
is replaced every year, its cost was not amortized. The energy
consumption of this device (including other accessories such as air
compressor etc.) was 5.83 kW.
Thus the cost of ozone system required = 34000 USD.