The problem of water pollution is a growing concern in China. About 183 typical water pollution incidents took place between 2001 and 2014 in China and were analyzed in this study. The results indicate that chemical pollution, heavy metal pollution, and algal blooms were the main types of contamination, accounting for 36%, 20%, and 9%, respectively, of the total pollution. Illegal discharges, pollution water leakage, and leakage during transport were the main sources of chemical pollution, accounting for 63%, 14%, and 12%, respectively. Illegal industrial discharges, leakage incidents, industrial production, and engineering construction pollution were the main contributors to heavy metal pollution, and accounted for 81%, 11%, 5%, and 3%, respectively. Industries should promote their environmental responsibility. It is also essential for government and industry to work together to strengthen supervision of industrial discharges and strictly control pollution sources. Alternative emergency response mechanisms for different pollution sources were analyzed allowing guidance to reduce pollution and providing a theoretical basis to establish and improve water pollution management.
With the continued rapid development of China's social economy, there is growing awareness of the strong connections between people's life and well-being, drinking water safety, and a clean environment. However, with continued industrial growth, illegal discharges from factories, and little attention to environmental protection, there are frequent water pollution incidents and the number of these incidents has increased year by year (Zhang et al. 2011a). There has also been growing awareness of the problems due to accumulated water pollution, including ammonia nitrogen pollution in the Tuojiang River in March 2004 (Cui & Liu 2006), nitrobenzene pollution in the Songhua River in November 2005 (Zhang 2006), the odorous water caused by algal decay in Taihu Lake in May 2007 (Zhu et al. 2015), and benzene pollution in Lanzhou in April 2014 (Li et al. 2015). Extensive water pollution incidents continue to occur and sometimes the providing of municipal tap water has been unexpectedly stopped due to pollution problems, forcing people to go to supermarkets to buy bottled water (Wang 2014). Thus, China's water pollution incidents continue to have a high rate of occurrence. Emergency treatment for water pollution incidents and the management of drinking water sources are frequent occurrences that have received public attention. On 24 April 2014 the People's Republic of China government approved changes in the Environment Protection Law (EPL-PRC), and the EPL-PRC came into force on 1 January 2015. The EPL-PRC reaffirms the government's responsibilities, and the EPL-PRC imposes stricter obligations on enterprises regarding pollution prevention and control. The law also provides for more severe penalties. Furthermore, the EPL-PRC allows for environmental public-interest litigation (EPL-PRC 2014).
Sudden water pollution incidents involve the unexpected release of pollutants into water bodies, resulting in water resource contamination within a short period and potentially causing emergency situations or other adverse impacts on society (Zhang et al. 2011b). These water pollution incidents present the characteristics of an emergency in that they create a disturbance and are harmful (Cui & Liu 2006), and include traffic accidents, a sunken ship in the process of chemical transportation, or accidental pollution due to industrial error. Leakage and release into water sources by traffic accidents or industrial accidents may result in the rapid spread of pollution, such as ammonia nitrogen in the Tuojiang River in March 2004. Given the prevalence of water pollution incidents, a crucial question is how to prevent such incidents and how best to deal with these incidents when they occur through effective emergency response. By statistically analyzing water pollution incidents, we identified some basic rules and characteristics of these incidents to provide the scientific basis for establishing and improving water pollution management (Ai & Liu 2013).
MATERIALS AND METHODS
This study used statistical data from the Ministry of Environmental Protection (MOEP), literature sources, newspaper, news media, and the internet. We compiled 183 sets of data from typical water pollution incidents that occurred from 2001 to 2014 in China. According to the classification and analysis of pollution sources, means, and hazards of these water pollution incidents, we present suggestions about emergency treatment technologies and emergency response management.
RESULTS AND DISCUSSION
Statistical analyses of typical water pollution incidents
With the continued rapid development of China's social economy, water pollution incidents showed an increasing trend (Figure 1(a)), and with the absolute value of GDP each year for the National GDP and the Industrial GDP having the same trend, this indirectly reflects that the GDP growth has certain effects on water pollution. Variance analysis with SPSS18.0 software showed that the incidence rate of water pollution was significantly higher (ANOVA, P < 0.01) after 2009, indicating that water pollution problems are becoming more serious. In addition, the number of industrial enterprises also has been gradually increasing, including chemical industry, ferrous and non-ferrous metals enterprises, which were closely associated with the occurrence of water pollution (Figure 1(b)). First, illegal industrial discharges have led to an increase of water pollution. Second, although industrial units have decreased after 2010, water pollution incidents have continued to increase, which also reflects another problem of water pollution, namely aging and poorly functioning equipment, and inadequate maintenance of equipment. Meanwhile, media and society have begun to pay more attention to water pollution incidents, indicating growing awareness, but this is also partly because serious water pollution problems are becoming more prevalent.
Analysis of pollutant types and treatment of typical water pollution incidents
In general, the water pollution source refers to the type of pollutant that causes water pollution. We classified the pollution source for 183 typical water pollution incidents that occurred in China in recent years, and identified eight categories including chemical pollution, heavy metal pollution, biological pollution, pesticide pollution, paper plant pollution, oil accident, household garbage pollution, and other unknown pollution types (Figure 2). Chemical pollution was the most common incident, which occurred in 65 incidents, accounting for 36%. Next frequent was heavy metal pollution, 37 incidents, accounting for 20%. Algal blooms attributed to water eutrophication occurred in 16 incidents, accounting for 9%. In addition, oil accidents, household garbage pollution, paper plant pollution, pesticide pollution, and other forms of pollution accounted for 10, 10, 5, 4, and 31 incidents, respectively, and 6%, 5%, 3%, 2%, and 17% of the total incidents, respectively. The result showed that water pollution source is becoming more diverse in China. The original environmental management regime should be quickly improved. Different pollutants will have different management ways and corresponding emergency treatment technologies. In addition, it is worth noting that other forms of pollution accounted for 17%, and further analysis found that some of these could result from more than one source of pollution including industrial discharge of mixed waste residue, natural disasters, and emerging contaminants. Therefore, we should strengthen the management of this kind of pollution.
Analysis of the chemical pollution incidents revealed that 45 incidents directly affected the drinking water source, 12 incidents indirectly affected the drinking water source, and eight incidents did not affect drinking water sources. We also analyzed the pollutants of incidents that directly affected drinking water (Figure 3(a)). These incidents included the exceeding threshold of benzene/alkene/phenol concentrations (seven incidents) (the exceeding threshold is defined as exceeding the environmental functional threshold, which is defined as a concentration range of the Chinese drinking water standard (GB5749-2006) to meet a certain function, for example, for drinking purposes), the exceeding threshold of aniline, phenol, and ammonia nitrogen (four incidents of each), the exceeding threshold of nitrite and fluoride (three incidents of each), and other pollution sources including one incident each of nitrate, total nitrogen, dimethylaniline, dimethyl disulfide, methyl tertiary butyl ether, chloroform/tetrachloromethane, tetrachloroethane, and chlorine. In addition, for 12 incidents, the specific pollutants were undetermined. Additional analysis of these incidents as shown in Figure 3(b) revealed that sulfide, cupric acid water, antibiotics, ammonia, and phosphor slag were the main pollutants. In recent years, the industrial production of different sewage types and amounts has gradually increased, and to avoid the cost of sewage treatment, many industries directly discharged sewage into the river. Additionally, pollution has resulted from the aging of industrial production equipment, which has led to increased frequency of accidental discharges, and traffic accidents resulting in leakage.
Analysis of heavy metal pollution incidents revealed that there were 21 incidents that directly affected a drinking water source, and 16 incidents that indirectly affected a drinking water source (Figure 4). Incidents that directly affected water sources included the exceeding threshold of arsenic (eight incidents), the exceeding threshold of cadmium (four incidents), the exceeding threshold of chromium and lead (two incidents each), and other solid waste resulting from coal mines, an iron mine factory and a smelting plant (five incidents). Incidents that indirectly affected water sources included the exceeding threshold of lead (four incidents), the exceeding threshold of cadmium (three incidents), and the exceeding threshold of chromium, arsenic, and thallium (two incidents each). Our analysis indicated that arsenic, cadmium, and lead played a dominant role in these metal contaminant incidents, and industrial illegal discharge was the main cause of this pollution.
Analysis of typical water pollution incidents that occurred in China in recent years indicated that the more prominent pollution sources include chemical pollution, heavy metal pollution, and biological pollution. Based on the characteristics of these three types, we would recommend safe, effective, and easily applied emergency treatment technologies. First, powdered activated carbon adsorption technology is the best available method to remove organic chemicals from water, such as was used to treat the benzene/phenylamine/nitrobenzene pollution in the Songhua River in November 2005. In this treatment, a combination of powdered activated carbon and granular activated carbon adsorption methods were used to adsorb organic pollutants followed by coagulation and settling using coagulant, filtering, and disinfection treatment with chlorine (Blum et al. 1994; Chen et al. 2007; Zhang & Chen 2009), to reach the drinking water standard. Second, chemical precipitation methods can effectively remove heavy metal pollution from water (Guo et al. 2011; Zhang et al. 2011a), including the weak alkaline coagulation process to remove cadmium pollution (Zhang 2006), chemical precipitation to remove lead at pH of 10.0–11.5 (Liu et al. 2015), and arsenic precipitation methods (Xu 2009). Finally, to target foul-smelling source water such as that caused by algal decay in the Taihu Lake in May 2007, integrated emergency treatment should include chemical precipitation, physical absorption and nutrient control (Guo 2007; Qin et al. 2010). The characteristics of pollutants should first be determined, and then emergency treatment should be applied using a combination of chemical precipitation and physical adsorption, with strict control of the nutrient content of regional water during post-processing to prevent the recurrence of algal pollution caused by eutrophication.
Analysis of types of pollution causing water pollution incidents
Our analysis showed that these incidents were mainly caused by illegal industrial discharges, sewage leakage incidents, transport leakage incidents, chemical factory explosions, factory collapse, industrial production, high background values, construction or household pollution, bacterial or virus infection, and algal bloom.
Analysis of the causes of water pollution incidents related to drinking water caused by chemical pollution revealed that 57 incidents of drinking water pollution have occurred, including industrial illegal discharges: 36 incidents (chemical factory: 17 incidents; paper factory: three incidents; and pharmaceutical factory: three incidents), accounted for 63%; industrial wastewater leakage incidents: eight incidents, accounted for 14%; transport leakage incidents: seven incidents (tank truck and ship accident), accounted for 12%; and two incidents of industrial production, accounted for 3%. In addition, there was one incident each of chemical plant explosion, factory collapse, high background values, and household garbage pollution (Figure 5).
Analysis of the different ways that heavy metal water pollution incidents related to drinking water revealed that 37 incidents of drinking water pollution incidents have occurred, including illegal industrial discharges (30 incidents, 81%), industrial wastewater leakage incidents (four incidents, 11%), industrial production (two incidents, 5%), and engineering construction pollution (one incident, 3%) (Figure 6).
The above analysis found that industrial illegal discharge was the predominant way, and second is industrial wastewater leakage and transport leakage. In order to save costs and increase profits, many industries did not have treatment facilities for waste disposal and instead directly discharged sewage into rivers, even though this process was illegal. Other problems included aging equipment, which could fail or leak and result in a water pollution accident. Additionally, during the transportation of materials, traffic incidents sometimes happen, resulting in chemical spills. Therefore, we should strengthen management and prevention.
Management with a focus on pollution sources
Our analysis of the pollution sources of chemical pollution found several contributing factors. First, industries (chemical plant, paper mill, cement mill, pharmaceutical factory, and others) discharge wastewater to avoid treatment costs. Second, some ammonia and benzene compounds resulted from aging and poorly functioning equipment, inadequate maintenance of equipment, and other less obvious environmental safety problems. Third, many industrial plants are located in environmentally sensitive areas with nearby drinking water sources, including rivers and reservoir areas (Zhang et al. 2011a). Some industries discharged the sewage water directly into drinking water source areas, causing nearby or downstream drinking water pollution, included high nitrate and toluene levels. Fourth, the excessive pursuit of economic profit and development caused some companies to ignore environmental risk assessment and safety requirements but continue production, potentially resulting in accidents including explosions. For example, the nitrobenzene spill in the Songhua River was triggered during the trial production of a new line at Jilin Petrochemical Company (Zhang et al. 2011a). Fifth, leakage from tank truck or ship accidents was the main cause of phenol pollution sources, and this leakage may be quite common (Zhang & Bai 2008).
The following countermeasures are proposed in view of the above problems. First, the government should strengthen supervision of industrial discharges, strictly control pollution sources, and require industries that are polluting to make rectifications or improvements within a time limit and not engage in production until corrections have been made. Second, to target problems resulting from industrial operation issues, such as aging equipment and transmission pipelines, malfunctioning equipment, inadequate maintenance, and other less obvious environmental safety problems, industries should increase equipment maintenance and overhaul as necessary, and also improve the safety awareness and operational skills of their employees. Businesses could also adapt more advanced systems of safety management, including hazard identification, risk evaluation, and risk control for dangerous chemicals. Additionally, efforts are required to classify and identify the risks of unknown and newly developed chemicals (Honkasalo 2000). Third, because many plant locations are located in environmentally sensitive areas, the government should compel industries to undergo reconstruction or relocation. Fourth, to decrease incidents resulting from problems during transportation, government and industries should improve tanker transportation safety management and improve the safety factor of tank trucks. Fifth, to counter the hazardous characteristics that can lead to accidents, industries should ensure production safety and strengthen dangerous goods management to effectively prevent accidents.
Additionally, the government should continue research on emergency treatment technologies and establish a dangerous pollution emergency hazard assessment system (Davies & Mazumder 2003; Liu & Zhou 2009). Improvements should also be made to facilitate and coordinate the ability of government and industries to work together on such issues. The government should strengthen the linkage mechanisms of all government departments and the local water company, and establish emergency monitoring plans, emergency treatment plans, expert teams for emergency response to environmental incidents, and the necessary emergency response facilities (Zhang & Chen 2009). Meanwhile, these water pollution incidents could be classified into four levels according to the incidents' nature and severity, and scope of the affected areas, which are the State, provincial, city, and county levels. When pollution incidents are occurring and public health and environmental safety may be affected, warning should be promptly released and emergency measures should be taken according to the severity of the incidents. Governments and enterprises should spare no efforts to carry out such work for emergency incidents. The department of House and Urban–Rural Construction is responsible for determining the layout of water treatment facilities and guiding the emergency drinking water supply. The department of Environment Protection is responsible for water source monitoring, water source protection, and the remediation of polluted areas. The department of Water Resources is responsible for supervision and management of water resources and conservancy engineering. The department of Health Inspection is responsible for quality assessment of drinking water, and medical emergency works (Zhang et al. 2011a).
Heavy metal pollution incidents were mainly due to the release of wastewater, waste gas, and waste residue by heavy industrial companies or improper handling of tail slag. These companies included refineries, chemical plants, electroplating factories, and others. To improve tail slag management, industries and the government should increase research into the emergency treatment of heavy metal pollution to develop corresponding emergency response plans. Algal blooms generally belonged to chronic pollution. Nutrient enrichment is the leading cause of water eutrophication. Long-term management of eutrophication should pay attention to anthropogenic nitrogen and phosphorus inputs (Qin et al. 2010).
Finally, unidentified pollution sources accounted for 17% of incidents. In accordance with the reason for this kind of pollution incident, industries should strengthen the management and supervision of waste slag. There is a need for studies to assess natural safety hazards to allow adoption of reasonable safety protection measures. At the same time, government and industries should increase management of emerging contaminants and develop appropriate emergency treatment and contingency plans for emerging contaminants to allow improved laws and regulations.
Management of illegal industrial discharge
Illegal industrial production and illegal discharges are the main sources of both chemical and heavy metal pollution, accounting for 63% and 81%, respectively. Therefore, the effective restraint of these illegal discharges is key to reduce additional pollution. First, industries should be held responsible for environmental protection and provide the first treatment in response to an accidental pollution incident. Second, the government needs to strengthen its supervision of industrial wastewater discharges, complete an environmental risk assessment, and increase monitoring and enforcement of illegal pollution. It is necessary to strengthen provisions for economic compensation and strictly implement the Environment Protection Law (EPL-PRC 2014), including penalties and the right to close down industries or limit production and demand reform. The government should take a ‘zero tolerance’ approach that compels industries that are illegally discharging pollutants to strengthen their own management. Moreover, their own production of wastewater or sewage must strictly undergo the corresponding wastewater treatment process and meet emission standards (Tan 2008). Industrial enterprises must strictly follow the control indicators of total emissions of key pollutants allocated to the enterprises. If the enterprises cannot reach the control indicators of total emissions of key pollutants allocated to them, the enterprises must implement stricter emission standards to share the control indicators. At the same time, the government should implement special supervision management and conduct a risk assessment for key pollution industries. Industries that discharge certain key pollutants must install and use monitoring equipment. Third, government should shut down the production and operation of illegal polluters and hold the owners of polluting companies responsible. Fourth, government should establish a credit archive of illegally discharging businesses, consider environmental risk with business risk, and form a diversified mutual constraint mechanism. Fifth, government should manage industrial discharges and pollution and improve the water pollution emission trading system. At present, China's water pollution emission trading system works at a local level, but there is no nationwide system with detailed laws and regulations (Liu 2014; Sun 2015), Thus the central government can construct a mature system of local emissions trading, and further improve and formulate a reasonable national water pollution emission trading market system. Additionally, enterprises should cooperate actively with the supervising authorities and prepare environmental impact assessments.
Overall, China will continue to be in a stage of industrialization for the near future, and water pollution incidents may continue to increase. A summary and statistical analysis of water pollution incidents indicates that establishing an effective emergency response mechanism is crucial. Water pollution incidents occurring in China from 2001 to 2014 were analyzed, and the results show that chemical pollution, heavy metal pollution, algal blooms, oil accidents, and household garbage pollution were the main contaminant sources. Further analysis showed that these incidents are mainly caused by illegal industrial discharges or leakage, transport leakage incidents, high background values, construction pollution, and household garbage pollution. Illegal industrial production and discharges are the main cause of both chemical and heavy metal pollution. Restraining of these illegal discharges can effectively reduce the pollution incidents. For improved management, we must perform emergency treatment research based on the most common pollutants and establish corresponding emergency response plans. Based on the most prevalent forms of pollution, central and local governments should take forceful measures to strengthen supervision of industrial pollution and strengthen relevant laws and regulations.
Given China's current economic development mode, water pollution incidents have gradually increased, and industrialization has contributed to long-term accumulated water pollution problems. Central and local governments should continue to maintain high values and support the development of emergency treatment technologies to respond to environmental pollution incidents with continued adaptation to respond to new pollutants. Finally, and most importantly, China should accelerate changes in its economic development mode as it moves away from its base of heavy-polluting industries. Industries and the public should continue to increase their awareness of environmental protection, advocate clean production, and establish a more environmentally friendly way of life that conserves and protects resources.
The authors gratefully acknowledge the funding for this study from the National Key Research and Development Program of China (2016YFC0502901), the National Basic Research Program of China (973 Program) through grant 2013CB956101, and the Natural Science Foundation of China (41175130).