Water quality in Cha-Am, Thailand is of particular concern because of the area's extensive oceanfront and its importance to the City’s tourism and real estate industries. PCSWMM was used to help improve water quality by simulating the effluent quality of the aerated lagoon system which treats municipal wastewater and consists of three ponds and a natural wetland.
The ponds were considered storage zones, and water quality sampling for Total Suspended Solid (TSS), Total Kjeldahl Nitrogen (TKN), Escherichia coli (E. coli), Chemical Oxygen Demand (COD), as well as evaporation measurements, were conducted on a bi-weekly basis for three months to calibrate the model.
Based on the observed water quality data distribution, Monte Carlo simulation was used (1,000 iterations) to receive the most probable input concentration for each pond and determine the appropriate treatment fractions for the model. Data on daily inflow rates, pump operation and bathymetric survey data also were obtained from the system operator as model input.
The dynamic wave method was used with observed inflow rates to generate a continuous water quality simulation from July 19th to September 12th, 2015. Observed mean treatment efficiency was 51.93%, 77.27%, 99.59% and 9.36% for TSS, TKN, E. coli and COD respectively; and observed concentrations at the outlet ranged between 10-25.5 mg/L, 0.98-3.92 mg/L, 0.1-260 CFU/100 ml and 48-119 mg/L for TSS, TKN, E. coli and COD respectively.
Able to accurately represent the outlet concentrations, the treatment fraction approach in PCSWWM was successful. This project has helped to protect Cha-Am’s oceanfront against pollution that threatens the City's tourism and real estate markets, and has assisted in informing individuals working toward improving water quality throughout the municipality.