An industrial wastewater with a flowrate of $4000\frac{m^3}{d}$ has a soluble COD concentration of $10,000$

$m\frac{g}{L}$ at $20C.$ Determine and compare the net operating costs or revenue for anaerobic versus

aerobic treatment based on the following key parameters and assumptions $($labor and maintenance

costs are omitted here$)$ for each:

Aerobic process:

Major aerobic treatment operating cost items are energy for aeration and sludge processing and

disposal.

COD removal efficiency $=99\%$

$g\frac{O_2}{g}$ COD removal $=1\mathrm{.}2$

Actual aeration efficiency $=1\mathrm{.}2kg\frac{O_2}{k}Wh$

Electricity costs for aeration $=$$$\frac{0\mathrm{.}2}{k}Wh$

Net sludge production $=0\mathrm{.}3g$ TSS $\frac{?}{g}$ COD removed

Sludge processing $\frac{?}{?}$ disposal cost $=$$$\frac{0\mathrm{.}5}{k}g$ dry solids

Anaerobic process:

Anaerobic operating cost items are related to raising the liquid temperature, and adding

alkalinity, versus the revenue from methane production.

Reactor temperature $=35C$

Heat exchanger recovery efficiency for raising liquid temperature $=80\%$

COD removal efficiency $=95\%$

$C{O}_2$ of gas phase $=35$ percent and $pH=7\mathrm{.}0$

Value of methane $=$$$\frac{5}{{10}^6}kJ$

Specific heat value $=4\mathrm{.}2k\frac{J}{k}\frac{g}{}C$

Cost of the required energy for heating $=$$$\frac{0\mathrm{.}08}{k}Wh,1\mathrm{.}0kWh=3\mathrm{.}6MJ$

Ignoring biomass production

The methane production at $35C=0\mathrm{.}40\frac{m^3}{k}g$ COD removed

Energy content of methane at standard conditions $=38,846k\frac{J}{m^3}$