Spatial variations of pollutants from sewer interception system overflow.

Sewer interception systems have been built along rivers in rapidly urbanizing areas to collect unregulated sewage discharges due to misconnections between storm sewers and sanitary sewers. During storm events, combined sewage might overflow from these systems into rivers through orifices and deteriorate water quality in rivers. Interception system overflows (ISOs) from different orifices in a sewer interception system might interact with each other, therefore pollutants from ISOs show a spatial variation. This paper aims to understand the spatial variation of pollutants from ISOs for informed decision making. In this study, an urbanized catchment in China is chosen as the study area, and the Storm Water Management Model (SWMM) is used to examine the spatial variation of pollutants from ISOs and to analyze the effect of sewer separation on ISOs. The results obtained from the case study indicate that: (1) Critical rainfall amounts which trigger overflows decrease downstream in an interception system while annual ISO volumes and pollutant loads from ISOs increase downstream; additionally, these variations are influenced by sizes and slopes of interceptors; (2) Runoff is the main source of COD from ISOs while sewage is the main source of NH3-N, and ratios of pollutants from sewage to ISOs increase downstream; (3) Sewer separation can significantly reduce pollutant loads from sewage to ISOs, but it cannot significantly reduce pollutant loads from runoff. In order to mitigate ISO pollution, it is suggested to increase conveyance capacities of interceptors in the downstream, separate sewage from runoff, and promote source control for urban runoff in highly urbanized areas.

The effects of low impact development on urban flooding under different rainfall characteristics.

Low impact development (LID) is generally regarded as a more sustainable solution for urban stormwater management than conventional urban drainage systems. However, its effects on urban flooding at a scale of urban drainage systems have not been fully understood particularly when different rainfall characteristics are considered. In this paper, using an urbanizing catchment in China as a case study, the effects of three LID techniques (swale, permeable pavement and green roof) on urban flooding are analyzed and compared with the conventional drainage system design. A range of storm events with different rainfall amounts, durations and locations of peak intensity are considered for holistic assessment of the LID techniques. The effects are measured by the total flood volume reduction during a storm event compared to the conventional drainage system design. The results obtained indicate that all three LID scenarios are more effective in flood reduction during heavier and shorter storm events. Their performance, however, varies significantly according to the location of peak intensity. That is, swales perform best during a storm event with an early peak, permeable pavements perform best with a middle peak, and green roofs perform best with a late peak, respectively. The trends of flood reduction can be explained using a newly proposed water balance method, i.e., by comparing the effective storage depth of the LID designs with the accumulative rainfall amounts at the beginning and end of flooding in the conventional drainage system. This paper provides an insight into the performance of LID designs under different rainfall characteristics, which is essential for effective urban flood management.

Assessment of environmental improvement measures using a novel integrated model: a case study of the Shenzhen River catchment, China.

Integrated water environmental management in a rapidly urbanizing area often requires combining social, economic and engineering measures in order to be effective. However, in reality, these measures are often considered independently by different planners, and decisions are made in a hierarchical manner; this has led to problems in environmental pollution control and also an inability to devise innovative solutions due to technological lock-in. In this paper, we use a novel coupled system dynamics and water environmental model (SyDWEM) to simulate the dynamic interactions between the socio-economic system, water infrastructure and receiving water in a rapidly urbanizing catchment in Shenzhen, China. The model is then applied to assess the effects of proposed socio-economic or engineering measures on environmental and development indicators in the catchment for 2011-2020. The results indicate that 1) measures to adjust industry structures have a positive effect on both water quantity and quality in the catchment; 2) measures to increase the labor productivity, the water use efficiency, the water transfer quota or the reclaimed wastewater reuse can alleviate the water shortage, but cannot improve water quality in the river; 3) measures to increase the wastewater treatment rate or the pollutant removal rate can improve water quality in the river, but have no effect on water shortage. Based on the effectiveness of the individual measures, a combination of socio-economic and engineering measures is proposed, which can achieve water environmental sustainability in the study area. Thus, we demonstrate that SyDWEM has the capacity to evaluate the effects of both socio-economic and engineering measures; it also provides a tool for integrated decision making by socio-economic and water infrastructure planners.

Spatial variations of storm runoff pollution and their correlation with land-use in a rapidly urbanizing catchment in China.

The composition of land use for a rapidly urbanizing catchment is usually heterogeneous, and this may result in significant spatial variations of storm runoff pollution and increase the difficulties of water quality management. The Shiyan Reservoir catchment, a typical rapidly urbanizing area in China, is chosen as a study area, and temporary monitoring sites were set at the downstream of its 6 sub-catchments to synchronously measure rainfall, runoff and water quality during 4 storm events in 2007 and 2009. Due to relatively low frequency monitoring, the IHACRES and exponential pollutant wash-off simulation models are used to interpolate the measured data to compensate for data insufficiency. Three indicators, event pollutant loads per unit area (EPL), event mean concentration (EMC) and pollutant loads transported by the first 50% of runoff volume (FF50), were used to describe the runoff pollution for different pollutants in each sub-catchment during the storm events, and the correlations between runoff pollution spatial variations and land-use patterns were tested by Spearman's rank correlation analysis. The results indicated that similar spatial variation trends were found for different pollutants (EPL or EMC) in light storm events, which strongly correlate with the proportion of residential land use; however, they have different trends in heavy storm events, which correlate with not only the residential land use, but also agricultural and bare land use. And some pairs of pollutants (such as COD/BOD, NH(3)-N/TN) might have the similar source because they have strong or moderate positive spatial correlation. Moreover, the first flush intensity (FF50) varies with impervious land areas and different interception ratio of initial storm runoff volume should be adopted in different sub-catchments.

[Validation of a prediction method for indoor air pollution].

The validation study of the prediction method for indoor air pollution was carried out by comparing the results of emission models based on data obtained in a large and a small emission chamber, with actual measured concentrations. A new decorated room was studied as a case. Emissions of complicated objects and simple surface layer materials were studied respectively in the large and small chamber and emission models were developed. Those models were based on the assumptions regarding mass conservation of substances and the hypothesis that pollutants were well mixed. The emissions of formaldehyde and TVOC (total volatile organic compounds) in the studied room were predicted by the method. The predicted concentration trend of pollutants was in accordance with the measured trend when some air exchange (0.03 ACH, air change per hour) was taken into account. The normalized standard errors of formaldehyde and TVOC pollution prediction were respectively 2.8% and 1.6%. Modeling analysis shows that the contribution to total formaldehyde pollution of the studied room was: furniture > paint > floor; the contribution to total TVOC pollution was: paint > floor > furniture. The results lead to the conclusion that this prediction method can well describe the pollution trend, can assess the contribution of different sources, can guide the choice of building materials and is an effective tool for indoor air pollution assessment and control.

Approach to and effectiveness of environmental risk education of public: case of indoor environmental risk consciousness in beijing.

Increasing concern regarding environmental risk in China has led to a need for education on environmental health and safety. In this paper, we report on four main ways to enhance environmental risk consciousness of the public. By investigating residents' indoor environmental risk consciousness in Beijing, we appraised the effectiveness of current environmental risk education approaches. Our investigation showed that the indoor environmental risk consciousness of most residents is high. Most residents have some environmental risk knowledge, have a strong desire to demand better quality of their living environment, and would like to invest in it. However, people's actual behavior in terms of reducing health risk factors fall comparatively behind. It is important to use all approaches to carry out environmental risk education. Not only should new knowledge be imparted, but the public should also be trained how to take precautions against pollution. The extension of education from campus to society is also necessary.