public static Wastewater CreateDomesticWastewater(string country = "US")
        {
            Wastewater w = new Wastewater();

            w.organic_compounds   = 100;
            w.inorganic_compounds = 100;
            w.nutrient            = 100;
            w.heavy_metals        = 100;
            w.TSS       = 100;
            w.pathogens = 100;

            Random random = new Random();

            if (country == "US")
            {
                w.BOD       = 200;
                w.COD       = 500;
                w.SS        = 200;
                w.N_T_Field = 40;
                w.P_T       = 10;
            }
            else if (country == "TW")
            {
                w.BOD       = random.Next(100, 150);
                w.COD       = random.Next(200, 400);
                w.SS        = 200;
                w.N_T_Field = random.Next(30, 40);
                w.P_T       = random.Next(3, 10);
            }
            else if (country == "NL")   // i.e., Dutch.
            {
                w.BOD       = 174;
                w.COD       = 471;
                w.SS        = SS_Default;
                w.N_T_Field = 44;
                w.P_T       = 6.7;
                w.TSS       = 223;
            }
            else
            {
                w.BOD       = BOD_Default;
                w.COD       = COD_Default;
                w.SS        = SS_Default;
                w.N_T_Field = N_T_Default;
                w.P_T       = P_T_Default;

                w.Phosphate_P = Unknown_Value_by_Random();
            }
            return(w);
        }
        public static Wastewater CreateIndustrialWastewater(string country = "US")
        {
            Wastewater w = new Wastewater();

            return(w);
        }