Weixing Ma

Effects of storm runoff on the thermal regime and water quality of a deep, stratified reservoir in a temperate monsoon zone, in Northwest China

Jinpen Reservoir is a deep, stratified reservoir in Shaanxi province, located in a warm temperate zone of Northwest China. Influenced by a temperate monsoon climate, more than 60% of the annual precipitation is concentrated from late summer to autumn (July-September). In recent years, extreme rainfall events occurred more frequently and strongly affected the thermal structure, mixing layer depth and evolution of stratification of Jinpen Reservoir. The reservoirs inflow volume increased sharply after heavy rainfall during the flooding season. Large volumes of inflow induced mixing of stratified water zones in early autumn and disturbed the stratification significantly. A temporary positive effect of such disturbance was the oxygenation of the water close to the bottom of the reservoir, leading to inhibition of the release of nutrients from sediments, especially phosphate. However, the massive inflow induced by storm runoff with increased oxygen-consuming substances led to an increase of the oxygen consumption rate. After the bottom water became anaerobic again, the bottom water quality would deteriorate due to the release of pollutants from sediments. Heavy rainfall events could lead to very high nutrient input into the reservoir due to massive erosion from the surrounding uninhabited steep mountains, and the particulate matter contributed to most nutrient inputs. Reasonably releasing density flow is an effective way to reduce the amounts of particulate associated pollutants entering the reservoir. Significant turbid density flow always followed high rainfall events in Jinpen Reservoir, which not only affected the reservoir water quality but also increased costs of the drinking water treatment plant. Understanding the effects of the storm runoff on the vertical distributions of water quality indicators could help water managers to select the proper position of the intake for the water plant in order to avoid high turbidity outflow.

Effects of rainfall patterns on water quality in a stratified reservoir subject to eutrophication: Implications for management.

The seasonal variation of hydrological conditions caused by shifting rainfall patterns observed in recent years has significant effects on water quality. High-volume inflows following heavy rainfall events that significantly disturb stratification lead to increased dissolved oxygen (DO) at the bottom of the reservoir, inhibiting the release of nutrients from sediments and causing a rapid reduction of algal biomass in the reservoir. However, the duration and extent of these effects depend not only on the frequency and intensity of heavy rainfall events but also on the period of thermal stratification in the reservoir. The effects of heavy rainfall events on water quality during three typical stratification periods of the reservoir were systematically investigated using extensive field data. The continuous heavy rainfall that occurred in September 2011 (stratification began to diminish) completely mixed the reservoir and produced a high concentration of DO along with a low phytoplankton concentration throughout the reservoir until stratification occurred the following year. Conversely, several days were required for anoxic conditions (in the hypolimnion) and cyanobacterial blooms to reappear after the storm runoff that occurred during the stable period of stratification (August 2012). In addition, the heavy rainfall that occurred in May 2013 accelerated the formation of an anoxic zone at the bottom of the reservoir and promoted cyanobacterial blooms due to the high nutrient input and the increased water temperature after the storm runoff ended. Water-lifting aerators (WLAs) were employed in the Shibianyu Reservoir to inhibit algal growth and to control the release of nutrients. Based on our field observations and theoretical analyses, optimized management strategies are recommended to improve water quality in the reservoir under different rainfall patterns at a reduced cost.

Indoor Heating Drives Water Bacterial Growth and Community Metabolic Profile Changes in Building Tap Pipes during the Winter Season

The growth of the bacterial community harbored in indoor drinking water taps is regulated by external environmental factors, such as indoor temperature. However, the effect of indoor heating on bacterial regrowth associated with indoor drinking water taps is poorly understood. In the present work, flow cytometry and community-level sole-carbon-source utilization techniques were combined to explore the effects of indoor heating on water bacterial cell concentrations and community carbon metabolic profiles in building tap pipes during the winter season. The results showed that the temperature of water stagnated overnight (“before”) in the indoor water pipes was 15–17 °C, and the water temperature decreased to 4–6 °C after flushing for 10 min (“flushed”). The highest bacterial cell number was observed in water stagnated overnight, and was 5–11 times higher than that of flushed water. Meanwhile, a significantly higher bacterial community metabolic activity (AWCD590nm) was also found in overnight stagnation water samples. The significant “flushed” and “taps” values indicated that the AWCD590nm, and bacterial cell number varied among the taps within the flushed group (p < 0.01). Heatmap fingerprints and principle component analyses (PCA) revealed a significant discrimination bacterial community functional metabolic profiles in the water stagnated overnight and flushed water. Serine, threonine, glucose-phosphate, ketobutyric acid, phenylethylamine, glycerol, putrescine were significantly used by “before” water samples. The results suggested that water stagnated at higher temperature should be treated before drinking because of bacterial regrowth. The data from this work provides useful information on reasonable utilization of drinking water after stagnation in indoor pipes during indoor heating periods.

Vertical Distribution of Bacterial Community Diversity and Water Quality during the Reservoir Thermal Stratification.

Reservoir thermal stratification drives the water temperature and dissolved oxygen gradient, however, the characteristic of vertical water microbial community during thermal stratification is so far poorly understood. In this work, water bacterial community diversity was determined using the Illumina Miseq sequencing technique. The results showed that epilimnion, metalimnion and hypolimnion were formed steadily in the JINPEN drinking water reservoir. Water temperature decreased steadily from the surface (23.11 °C) to the bottom (9.17 °C). Total nitrogen ranged from 1.07 to 2.06 mg/L and nitrate nitrogen ranged from 0.8 to 1.84 mg/L. The dissolved oxygen concentration decreased sharply below 50 m, and reached zero at 65 m. The Miseq sequencing revealed a total of 4127 operational taxonomic units (OTUs) with 97% similarity, which were affiliated with 15 phyla including Acidobacteria, Actinobacteria, Armatimonadetes, Bacteroidetes, Caldiserica, Chlamydiae, Chlorobi, Chloroflexi, Cyanobacteria, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Proteobacteria, and Verrucomicrobia. The highest Shannon diversity was 4.41 in 45 m, and the highest Chao 1 diversity was 506 in 5 m. Rhodobacter dominated in 55 m (23.24%) and 65 m (12.58%). Prosthecobacter dominated from 0.5 to 50 m. The heat map profile and redundancy analysis (RDA) indicated significant difference in vertical water bacterial community composition in the reservoir. Meanwhile, water quality properties including dissolved oxygen, conductivity, nitrate nitrogen and total nitrogen have a dramatic influence on vertical distribution of bacterial communities.

Dynamic characteristics of nutrients and causal analysis in eutrofic reservoir: a case study of Shibianyu reservoir

AbstractEutrofication and the resulting proliferation of phytoplankton have become a serious problem of reservoirs around the world. In order to make effective algae control measures through reducing concentrations of nutrients, in this study both the dynamic characteristics of nutrients and its source were investigated in Shibianyu reservoir located in north-western of China. The results showed that a 2.8 mg/L of annual average total nitrogen concentration in Shibianyu reservoir was observed, which exceeded the source water quality standard during whole monitoring years, and the maximum concentration reached 5.1 mg/L in spring. Moreover, it was observed that there is high total phosphorus concentration during the mixing period in winter or the heavy rainfall period. The hypolimnion became anoxic during the stratified period to increase the release of nutrients from the sediments. The nutrients of upper water increased rapidly when stratification disappeared because the high concentrations of pollutants i...

The Effects of Storm Runoff on Water Quality and the Coping Strategy of a Deep Canyon-Shaped Source Water Reservoir in China

Storm runoff events in the flooding season affect the water quality of reservoirs and increase risks to the water supply, but coping strategies have seldom been reported. The phenomenon of turbid current intrusion resulting in water turbidity and anoxic conditions reappearing after storm runoff, resulting in the deterioration of water quality, was observed in the flooding season in the deep canyon-shaped Heihe Reservoir. The objective of this work was to elucidate the effects of storm runoff on the Heihe Reservoir water quality and find a coping strategy. In this study, an intensive sampling campaign measuring water temperature, dissolved oxygen, turbidity, nutrients, and metals were conducted in the reservoir over a period of two years, and the water-lifting aerators were improved to achieve single aeration and a full layer of mixing and oxygenation functions using different volumes of gas. The operation of the improved water-lifting aerators mixed the reservoir three months ahead of the natural mixing time, and good water quality was maintained during the induced mixing period, thereby extending the good water quality period. The results can provide an effective coping strategy to improve the water quality of a source water reservoir and ensure the safety of drinking water.

Water Quality Improvement by Water-Lifting Aerators

This chapter presents the results of water quality improvement performed in three different types of Chinese reservoirs after the installation of water-lifting aerators and the improved equipment during the period of 2006–2013. The results showed that the technology of water-lifting aerators can effectively control the release of endogenous pollutants, inhibit algal blooms, remove volatile contaminants (VOC), and reduce the pollution load in reservoirs. Compared to the same conditions, the algae can be reduced by 75–90 %, ammonia can be reduced by 69–95 %, TP can be reduced by 63–97 %, Fe/Mn can be reduced by 67–90 %, VOC can be reduced by 80–90 %, TN can be reduced by 19–32 %, and CODMn can be reduced by 16–26 %.

Typical Reservoir Pollution Source Analysis

Exogenous and endogenous pollutions are the two main kinds of pollution sources that result in the deterioration of water quality in reservoirs. Exogenous pollution is derived from the environment surrounding reservoirs, including industrial wastewater, sewage runoff, solid waste, meteoric waters, and surface runoffs from urban, agriculture, and pastoral areas. Endogenous pollution is mainly caused by the pollutants released from sediments, the fecundity and death of phytoplankton and aquatic plants, and aquaculture. The pollution source analysis contributes to a deep research on the mechanism, process, and control of reservoir pollution, and provides basic theory and technology supports for improving the water quality. In recent years in China, with the further understanding about the importance of water protection, especially with the significant progress of water protection, the exogenous pollution of water sources has been or is being effectively controlled. Endogenous pollution becomes the dominant factor affecting water quality. In this chapter, the exogenous and endogenous pollution sources, classification, and status in China are concretely discussed and four reservoirs in China named Jinpen, Shibianyu, Zhoucun, and Fenhe were examined to elaborate these issues. For exogenous pollution, the pollution sources, main pollutants, and the load of every kind of exogenous pollutant in Shibianyu Reservoir were shown to indicate that runoff after rainfall scour was one of the main reasons for TN and TP increase. For endogenous pollution, pollutants release from sediment caused by forward temperature stratification in Heihe Reservoir and backward temperature stratification in Fenhe Reservoir were analyzed. The results showed that temperature stratification would result in the release of nitrogen and phosphorus from sediment. Moreover, endogenous pollution caused by algae reproduction and aquaculture in Zhoucun Reservoir were also discussed point for point and the data indicated that the algae in this reservoir were highly correlated with temperature, pH, turbidity, and total phosphorus, but inversely correlated with the ratio of nitrogen and phosphorus. Decades of cage culture was one main reason for the heavy pollution in sediment of Zhoucun Reservoir.

Application of Water-Lifting Aerators in Reservoirs

Based on the water quality problems in three typical Chinese reservoirs, this chapter introduces the functions of water-lifting aerator (WLA) technology used in these reservoirs for water quality improvement and its engineering solutions. The main contents include: the composition of WLA systems, the layout and installation of WLAs and the compression pipeline, operation conditions, and parameters of WLA systems, and the improvement of WLA systems in order to solve the problems that occur during the operation period.