Wastewater treatment plants are required, by regulation, to discharge 0 kg of phosphorus (P) for new or expanded wastewater treatment plants. The amount of phosphorus removed is calculated using mathematical formulae, and dischargers must remove 4 kg of phosphorus for every 1 kg discharged into watercourses. The use of a trading programme improves water quality compared with traditional wastewater treatment since other pollutants are removed by the nonpoint pollution control methods, and not just phosphorus.