Water Pollution and Water Quality Control of Selected Chinese Reservoir Basins

Reservoirs are artificially formed in the bed of a river by building a dam, which intercepts the runoff. They have narrow surface but great depth, and the water level changes significantly during flooding. The mean depth of Chinese reservoirs is around 20–50 m.

China is a country with numerous lakes and reservoirs. There are more than 2300 lakes with individual areas of more than 1 km², and the total area is 70,988 km², with the fresh water of 2.25 × 10¹¹ m³. There are 86,852 reservoirs and the total volume is 4.13 × 10¹¹ m³. The total volume of fresh water in lakes and reservoirs is, therefore, 6.38 × 10¹¹ m³. They are the important fresh water source of drinking water in China.

Since the 1950s, the pollution of reservoirs has become serious. The water quality in reservoirs is deteriorating due to population growth, industrialization, and urbanization. In order to clarify the characteristics of water quality change in reservoirs, in-situ monitoring of water quality and phytoplankton were conducted in Jinpen Reservoir, Shibianyu Reservoir, Zhoucun Reservoir, and Zhelin Reservoir.

This chapter discusses the change of water quality in reservoirs in terms of eutrophication, algae pollution, and endogenous pollution. The results indicate that Zhelin Reservoir, Jinpen Reservoir, and Shibianyu Reservoir are in the middle eutrophic state, while Zhoucun Reservoir is in the eutrophic state. All the reservoirs suffer from algal blooms in July and August, with cyanobacteria dominating. Stratification, a very common phenomenon, occurs in the reservoirs mentioned above, can cause the decline of bottom dissolved oxygen, aquatic ecological environment deterioration, and the release of pollutants from sediment.

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.

Source water protection is the prerequisite for drinking water safety, and a reliable source of water is the guarantee for a safe water supply. Source water protection is via administrative, legal, economic and technical methods, and management to ensure the quality and quantity of source water. This chapter mainly elaborates on the protection of source water reservoirs based on the three following aspects: planning, division, and management. Protection planning includes isolation protection engineering planning, ecological restoration planning, and emergency capability planning. The division of protection areas is introduced based on three aspects: principle, method, and signs. The protection management includes water quality monitoring and evaluation, pollution management, ecological management, and integrated water management. In addition, three examples of reservoir water protection are illustrated, providing a reference for reservoir protection.

The concentration of inorganic phosphorus (IP) in the surface sediment of each of the studied reservoirs ranged from 208.8 to 636.7 mg/kg. The concentration of Fe/Al-P in the surface sediment in the four reservoirs ranged from 82.1 to 216.7 mg/kg, and the average value was 129.6 mg/kg, accounting for 11.54–18.1 % of the sediment total phosphorus (STP) content. The highest proportion of IP is observed in Yuqiao Reservoir, and Jinpen Reservoir had the lowest proportion. In addition, the results indicated that the Ca–P concentrations of the four reservoir sediments are in the range 180.7–303.4 mg/kg, with an average value of 247.1 mg/kg, accounting for 22.33–37.1 % of the STP. The content of organic phosphorus (OP) in the reservoir surface sediment is in the range 64.2–201.8 mg/kg, accounting for 9.85–18.52 % of STP content. The ion exchange nitrogen (IE-N) content (mg/kg) in reservoirs is significantly different. The IE-N content of Shibianyu Reservoir is much higher than that of other reservoirs, accounting for 18.35 % of the total nitrogen (TN). The IE-N in the studied reservoirs accounted for 15.33–18.35 % of the TN. IE-N exists in three different speciations: the concentration of ammonia is much higher than that of nitrate and nitrite, and the concentration of nitrite is the lowest. The cloning and sequencing results showed that microorganisms were made up of ten major categories, including shaped bacillus, Chloroflexi, Verrucomicrobia, Bacteroides, Acidobacteria, thick wall bacteria, actinomycetes, Gemmatimonadetes, Nitrospirae, and Planctomycetes, in the Jinpen Reservoir sediments.

Nitrogen is not only a basic constituent element of life, but it is also one of the key elements causing eutrophication. It has an important effect on nutritional status and water quality in lakes and reservoirs. Inorganic nitrogen, including ammonia (NH₄ ⁺) and nitrate (NO₃ ⁻), often occurs following nitrification and denitrification reactions in a multiphase interface with the change of dissolved oxygen (DO) and redox. In addition, the extent of heavy metals is diffused from sediments to overlying water. It may cause potential harm to the water quality of the reservoir. This chapter is separated into two parts: (1) The release of nitrogen and phosphorus from sediment is investigated in typical Chinese reservoirs; (2) The release of metals from sediment is investigated in typical Chinese reservoirs.

The sediment in reservoirs is mainly derived from the sedimentation of suspended grains, such as organic particles and inorganic minerals, carried by runoff scouring from vegetation. There are three parts in this chapter: (1) Effects of pollutants released from sediment on water quality; (2) Effects of metals released from sediment on water quality; (3) Algal blooms and their impact on water quality. The decrease of the oxidation–reduction potential (ORP) in a multiphase interface under anaerobic conditions resulted in the increase of soluble ferrous hydroxide. Phosphate combining with iron hydroxide in sediment is released to interstitial water and then diffused into the overlying water. In addition, the metabolism of microbes resulted in the decrease of the ORP in anaerobic conditions, promoting the release of soluble iron in sediment and then causing the huge release of phosphorus. The release of endogenous phosphorus from sediment under anaerobic conditions resulted in the significant increase of PO₄ ³⁻ in the overlying water. The release of phosphorus from sediment depends on the conditions of the ORP.

In this chapter, the common technical methods, including physical, chemical, and ecological control techniques, for improving the water quality of lakes and reservoirs are briefly introduced. The physical control technologies mainly include the mixing–oxygenating technology, dilution and scour, sediment dredging, and coverage. The chemical control technologies mainly include phosphorus precipitation and passivation, restoration of acidified lakes or reservoirs, and sediment oxidation. The ecological control technologies mainly include bioremediation, phytoremediation, and biomanipulation remediation. By analyzing and comparing the tested data, for water sources such as reservoirs, the mixing–oxygenating technology is more suitable for decreasing endogenous pollution and controlling eutrophication.

This chapter introduces the technical background and water quality improvement principles of water-lifting aeration, and describes the methods of designing and optimizing the structure of a water-lifting aerator. The mixing and oxygenation performance of a water-lifting aerator is analyzed using established mathematical models of hydrodynamics and oxygen transfer for the aeration chamber of a water-lifting aerator. Application conditions for controlling the internal water quality pollution and algal blooms by using water-lifting aeration technology are analyzed and discussed. With the help of the computational fluid dynamics (CFD) method, the flow fields outside a water-lifting aerator are numerically simulated, and the effective radius of the algae inhibition zone analyzed and determined. The proper installation height and outflow configuration of a water-lifting aerator are also numerically analyzed and optimized.

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.

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 COD_Mn can be reduced by 16–26 %.

Reservoir water qualities are regulated by sediment/water microbial functional communities harbored in the drinking water reservoir ecosystem. However, little is known about reservoir sediment-/water-associated bacterial, fungal, archaeal, sulfate reducing bacterial, and actinomycetes populations. In this chapter, we used nested polymerase chain reaction (PCR) denaturing gradient gel electrophoresis (DGGE), substrate utilization profiling (named BIOLOG), quantitative PCR, clone sequencing, and high-throughout pyrosequencing methods to describe the microbial functional composition in drinking water reservoir ecosystems. Based on these backgrounds, there are five parts in this chapter, as follows: (1) Microbial metabolic activity in the sediments of drinking water reservoirs; (2) Bacterial composition in drinking water reservoir sediments; (3) Fungal composition in drinking water reservoir sediments; (4) Archaeal composition in drinking water reservoir sediments; (5) Carbon utilization patterns of reservoir water bacterial communities. The results from this chapter will undoubtedly broaden our understanding of reservoir functional microbial species harbored in these freshwater environmental conditions. The specific microbial species might be used for reservoir water bioremediation engineering processes.

During the past few decades, more and more people have poured nitrogen into the fresh water ecosystem, leading to serious environmental problems, such as eutrophication, algal bloom, and unsafe water, especially in drinking water reservoirs. Nitrogen removal in freshwater ecosystems is important for water utilization processes. Physical (air stripping) and chemical techniques (chemical precipitation) are widely used to remove nitrogen from wastewater, as the traditional biological method (nitrification by autotrophs under aerobic conditions and denitrification by heterotrophs under anaerobic conditions) is impractical. Conventional biological denitrification only occurs under anaerobic or anoxic conditions with the reduction from nitrate to nitrogen gas. Oxygen inhibits the reaction steps, which makes them impractical in natural waters, especially in reservoirs. However, few studies have focused on aerobic denitrifiers’ characteristics for removing nitrogen from oligotrophic drinking water reservoirs. To end this, we isolated several strains using enrichment and screening processes. We found that some strains have perfect performance on nitrogen removal in aerobic conditions with low pollutant concentration. Therefore, the objectives of the present work were to determine the taxonomic status using the 16S rRNA method, and to determine nitrogen removal performance in nutrient medium. The results can be useful for applications of aerobic denitrifiers for micropollution reservoir bioremediation. There are two parts in this chapter: (1) Screening and isolation of oligotrophic aerobic denitrifying bacteria; (2) Denitrification performance in pure culture conditions. The results of this part demonstrated that oligotrophic aerobic denitrifying bacterial species had aerobic denitrification ability, and resist a low carbon to nitrogen ratio, therefore, provided the scientific evidence for micropolluted source water bioremediation processes in situ.

In situ biological purification technology has been widely used in the engineering of environmental pollution treatment, since it is a more convenient and effective approach, with low cost. Therefore, the potential risk to the safety of biological agents should be seriously taken into consideration. The efficient aerobic denitrifying bacteria strain HF3, which is isolated and cultured in a low-nitrogen medium in order to remove nitrogen under oligotrophic conditions, has been used for bioremediation treatment, with effective and reliable ability in removing the nutrients of aquatic environments. Different to other biological agents, the efficient strain used for biological purification was cultured from raw water, and was isolated among indigenous bacteria. It is, therefore, the inferior species, and pathogenic bacteria had been excluded during the isolation. In addition, non-native application of the efficient strains which had a high environmental risk could be avoided during the application. In this chapter, we discuss the safety of the efficient strain HF3 by three aspects: biological safety on drinking water quality, ecological safety on indigenous microorganisms, and toxicological safety on aquatic animals. The results showed that the efficient aerobic denitrifying bacteria strain HF3 had no significant effect on the microbial community, and had no toxicity on mice, luminescent bacteria, or zebrafish. The efficient strain HF3 could be inactivated without any influence on the inactivation efficiency. The results suggest that the biological agent used for bioremediation treatment is safe and poses no risks to the urban drinking water supply, which could provide theoretical guarantees for the security of a wider range of application. It is important to reveal the effect and ecological assessment of microbial remediation. Therefore, in this chapter, we describe the effect and ecological assessment of the microbial remediation process.