Study on the intensified reduction of farmland non-point source pollution in winter using thermally insulated ecological shallow ditch

Abstract

Ecological shallow ditch is one of the effective methods to improve non-point source pollution of farmlands. However, during winter when the temperature is low, the operation capacity of the common ecological shallow ditch (CESD) is not satisfactory. In the present study, a thermally insulated ecological shallow ditch (TESD) was constructed, and the pollutant removal efficiency of the two ecological shallow ditches (thermal-insulation type versus common type) was compared. The changes in the number of bacteria inside these two types of shallow ditches were studied, and the underlying mechanism was analysed. The results showed that the thermally insulated ecological shallow ditch could partly reduce the adverse effects of low temperature and keep the surface temperature above 10°C. After 18 days of observation in the winter, the removal rates of COD, TN and TP in the effluent were respectively 1.3 times, 2.5 times and 1.3 times higher than those of the common type, and the concentration of bacteria in each site was also higher for TESD. The oxygen content in the soil layer and filler layer in TESD increased. Moreover, TESD also demonstrated higher microbial activity and more active plant growth than the CESD.