[Treatment Effects of Earthworm Constructed Wetlands in Different Working Conditions].

The feasibility of a new sludge treatment technology of earthworm constructed wetlands was tested by adding earthworm into the traditional sludge dying reed beds. The dewatering and stabilization effects of the upper layer sludge were tested under different sludge loading rates of 48, 65, 80 kg·(m2·a)-1, different earthworm stocking densities of 0, 0.43, 0.54, 0.65 kg·m-2 and different sludge loading frequencies. The results indicated that it was feasible to provide a shelter for earthworm during the loading period by setting a damper with a buried depth of 10 mm. The addition of earthworm could effectively improve the dewatering and stabilization effects of earthworm constructed wetlands, by lowering the DHA and decreasing the moisture content and VS of sludge by 15% and 10% respectively. The stabilization effects of earthworm constructed wetlands reached the best under the stocking density of 0.65 kg·m-2. With the increase of sludge loading rate and decrease of loading frequency, the running efficiency of earthworm constructed wetlands would be worse.

[Characteristics of rainfall and runoff in urban drainage based on the SWMM model.] / 基于SWMM模型的城市排水区域降雨及地表产流特征.

The characteristics of 235 rainfall and surface runoff events, from 2009 to 2011 in a typical urban drainage area in Shanghai were analyzed by using SWMM model. The results showed that the rainfall events in the region with high occurrence frequency were characterized by small rainfall amount and low intensity. The most probably occurred rainfall had total amount less than 10 mm, or mean intensity less than 5 mm·h-1,or peak intensity less than 10 mm·h-1, accounting for 66.4%, 88.8% and 79.6% of the total rainfall events, respectively. The study was of great significance to apply low-impact development to reduce runoff and non-point source pollution under condition of less rainfall amount or low mean rainfall intensity in the area. The runoff generally increased with the increase of rainfall. The threshold of regional occurring runoff was controlled by not only rainfall amount, but also mean rainfall intensity and rainfall duration. In general, there was no surface runoff when the rainfall amount was less than 2 mm. When the rainfall amount was between 2 to 4 mm and the mean rainfall intensity was below 1.6 mm·h-1, the runoff was less than 1 mm. When the rainfall exceeded 4 mm and the mean rainfall intensity was larger than 1.6 mm·h-1, the runoff would occur generally. Based on the results of the SWMM simulation, three regression equations that were applicable to regional runoff amount and rainfall factors were established. The adjustment R2 of the three equations were greater than 0.97. This indicated that the equations could reflect well the relationship between runoff and rainfall variables. The results provided the basis of calculations to plan low impact development and better reduce overflow pollution in local drainage area. It also could serve as a useful reference for runoff study in similar drainage areas.