There are some electroplating factories around the Kiang valley area, that do not have good facilities for wastewater treatment. Wastewater from the electroplating process contains cyanide and metallic ions like copper, nickel, chromium, lead, zinc, silver, and others which is discharged directly into drains. Department of Environment (DOE) is the regulatory body for wastewater effluent quality through the Environmental Quality Act 1974 and its regulations such as the Environmental Quality (Sewage) Regulations 2009 and Environmental Quality (Industrial Effluent) Regulations 2009. The quality of surface water is determined by the Water Quality Index and the suitability of surface water for irrigation is based on the designated classifications in the National Water Quality Standards for Malaysia established by DOE.
A silver (Ag) electroplating plant producing a wastewater stream contains 5 wt% Ag which needs to be treated before disposal. The wastewater is fed to a treatment tour where 95% of the fed Ag is recovered, while residual liquid water is sent to a waste pond. The maximum capacity of the treatment tour is 6000 kg wastewater/hr. When the fed wastewater stream is at a rate higher than the capacity of the treatment tour, the excess wastewater bypasses the unit and combines with the residual liquid water from the treatment tour and goes to the waste pond.
Choose one Mo from the given range, draw a process flow diagram of the system and determine the composition of each stream for the three M conditions.
The company plan to increase the capacity and efficiency of the treatment tour, please comment and justify the need. Support the justification by comparing the allowable concentration of Ag in disposed wastewater by the National Water Quality Standards, DOE Malaysia with the final concentration of Ag in the residual liquid waste before sending it to the waste pond. The justification should be clearly stated and supported with reference.