The development of a natural heating technology for constructed wetlands in cold climates

Composting of different ratios of pig manure to reed straw was studied to be a natural heating technology of constructed wetlands (CWs) in winter. Among the mixtures of pig manure and reed straws in different ratios, the pure pig manure was the most suitable compost material for the heating system of CWs in cold climates and its life expectancy was about 40 days. The one-year validation test in real-scale CWs with composting of pure pig manure as natural heating system in winter proved that the heating system of CW with pure pig manure as compost material can work effectively and enhance the pollutants removal rate in winter. The water temperatures inside the CW with heating system in winter (15.7-21.7 °C) were higher than that of CW without heating system (9.2-13.6 °C). The mean areal load reduction of TN and of NH3-N in winter of CW with heating system was 1.008 g/m2/d and 1.08 g/m2/d, which was about 120% more than that of CW without heating system.