This paper focus on the use of Carbon dioxide (CO2) instead of sulphuric acid (H2SO4) in a modified wastewater treatment scheme. Over 90% of the vented CO2 from an ammonia plant was used in this scheme, CO2 was directly injected into the wastewater to neutralize it, by reducing the pH to acceptable standard (7.0). This was achieved because the CO2 produces carbonic acid (H2CO3). The use of this process produced a better overall effluent quality of wastewater (pH, 7.56; TDS, 155.15 ppm; Heavy metal, 1.49 ; ppm) as against the use of H2SO4 (pH, 8.77; TDS, 1000 ppm; Heavy metals, 2.90 ppm) which has to be purchased. Savings in operating costs amount to N13,710,600 ($100,813.00) per year, with improved treatment efficiency. Additional long term savings are projected because of reduced shutdown time. However, it was observed that it took 45 minutes longer to achieve this result with CO2.