Tong Yindong is a teacher at the College of Environmental Sciences, Tianjin University。

       If you don't know the main points when we're doing the test, you just go up like crazy, and some of them are always right. We're finding that urban sewage treatment plants in China are suddenly in the same situation. We don't even know whether urban sewage treatment plants are useful, so we build like crazy, thinking that the more we build, the better. But the truth is, we don't know. One of the things I've done over the last three years is to think about whether it's worth it to spend all that money.

        Tong Yindong: Hello, everyone. My name is Tong Yindong. I'm from The School of Environment, Tianjin University. Today we are talking about environmental pollution.

       The main reason I'm here today is because of a job I've done over the last three years. As we all know, there are many sewage treatment plants in Chinese cities, especially in big cities. We can use sewage treatment plants to wash vegetables, bathe and flush toilets in our daily life. But what about those sewage plants? In the actual water environment, is it useful for the treatment of the disease of affluence in our lakes?

       The purpose of doing this is actually mainly from two place names, the first place is called Qinwu. Qinwu is a small mountain village where I was born. I come from Zhejiang province. The distance from Shanghai is about 230 kilometers as the crow flies. It takes four or five hours by car.

        I just go back to the village once a year during the Spring Festival. I was going back in 2002 or 2003 and all of a sudden I saw this thing.

       If you don't look closely, you'll probably think it's the landlord's swimming pool. But it is not the landlord's swimming pool, nor is it the landlord's fish pond, in fact it is an oxidation pond.

       What is an oxidation pond? Sewage is produced in cities and also in rural areas. Domestic sewage generated in rural areas will be collected into the oxidation pond. After initial microbial decomposition in the oxidation pond, this water will be released into the water environment. Of course, this kind of sewage treatment is actually very low-level, but it is not cheap to build such an oxidation pond, probably around 2 million yuan.

       The cost does not include land acquisition, which is unclear. The oxide pond I'm talking about cost $2 million to build, but it still costs about $500,000 a year to run. This is what happened in our village, Qinwu.

       In the same year, something appeared somewhere else. It's something that most of you have heard of, and it touches all of us, and it's the urban sewage treatment plant, which is where our toilet flusher ends up every day.

       Although I left the village, I stayed in the town for a long time. I found that so early in 2005, such a oxidation pond has appeared in such a beautiful village, such an insignificant town has appeared in the town sewage treatment plant. But we never knew how much these things contributed to the water environment, or to the algae blooms in Taihu.

       Let's start with two sets of data. The first data is from the national sewage treatment plants in 2015, when there were more than 5,000 centralized sewage treatment plants in cities and towns. I'm talking about urban centralized sewage treatment plants, not some factories, chemical plants, the state will require them to have some additional sewage treatment plants of their own。

城市污水處理量和處理率

農(nóng)村衛(wèi)生廁所覆蓋人口和覆蓋率

       China's urban sewage treatment rate has reached 84 percent, which means that almost every city and every county has a sewage treatment plant. If you build a sewage treatment plant that handles 5,000 to 10,000 tons of water a year, it would cost about 50 million dollars to build.

       But if you're going to divert water to a sewage treatment plant, it will include all kinds of pipe networks. For example, you often see places where the road is taken off and covered over, and a lot of times it's a sewage pipe network. So if the sewage treatment pipe network is added, a city generally needs to build a sewage treatment plant of about 150 million yuan.

       The above refers to the construction cost, as well as a large number of labor costs and maintenance costs every year. For example, some strains need to be replaced, and some sewage treatment plants need to be maintained regularly. These costs are about 20 million yuan per year. So a sewage treatment plant, the cost to build plus the annual operating cost, is actually a very large number.

       Another figure comes from the China Environmental Statistics Yearbook. From 2006 to 2014, the central government directly invested 300 billion yuan in sewage treatment. What I'm talking about here, of course, is direct input from the central government, not including local governments, which usually provide twice as much.

       So if we calculate by the local supporting facilities twice, from 2006 to 2014, we have used about 1 trillion to treat urban sewage, but we never know whether it has any effect.

       Seeing that algae is still erupting in Taihu Lake, many people must have questions. So we ask a question: we spent so much money, the algae in Taihu lake still continue to erupt, and then why?

       It occurred to me that I had gone to the statistics to see if anyone in the country knew how effective sewage treatment plants were, and found no one. This reminds me of an example from high school. Before the college entrance examination, especially in Zhejiang province, the most we did was the simulation paper of Huanggang Art of War, and there seemed to be Wang Houxiong.

       When we finish the simulation paper, we will generally be divided into the following categories: first, he finished the simulation paper, directly to the answer and went to play. The second type of person, he will re-score the answer. Let's say it's 100, he gets 60, doesn't matter, he just leaves. There is a third group of people who tend to be the best academically. After he gets his answer right, even if he gets 95, people are still not satisfied with the 5. To find the reason of the problem, because to find the reason of the mistake will not make a mistake next time。

       As you probably know, most good people are actually the third kind of students. It suddenly occurred to me that if we take China's water pollution as a problem we are facing, then the construction of urban sewage treatment plants is a way to answer this question.

       If you don't know the main points when we're doing the test, you just go up like crazy, and some of them are always right. We're finding that urban sewage treatment plants in China are suddenly in the same situation. We don't even know whether urban sewage treatment plants are useful, so we build like crazy, thinking that the more we build, the better. But the truth is, we don't know. One of the things I've done over the last three years is to think about whether it's worth it to spend all that money.

       Of course, there are a lot of ecosystem problems in lakes, and there are a lot of pollution, so what we're talking about here is whether sewage treatment plants can effectively alleviate the diseases of affluence in lakes.

       First let's look at what is the disease of affluence in lakes. The disease of affluence is simply a manifestation of eutrophication in water. What does eutrophication mean? It refers to the phenomenon of water pollution caused by excessive nitrogen and phosphorus nutrient elements in water.

       Eutrophication generally takes two forms. The first is the algal type eutrophication that we have just seen. You can't catch something like paint floating on the lake. You catch it and it's gone, like sand.

       There is another type called grass-type eutrophication. Grass-type eutrophication is particularly abundant in urban river channels, such as water hyacinth, which can be often seen in river channels.

       Most people probably know that water hyacinth is an alien species, and the explanation we give is that this alien species is particularly good for our water environment. What we don't know is that there are so many Water hyacinth in China, essentially because there are so many nutrients in our lakes. Of course, in general, the direct consequences of algal eutrophication are much larger than those of grass eutrophication.

       Why is that? Because the growth cycle of algae is very short, usually only about 7 to 10 days, after which the algae will die. Organic matter decomposes after death, and in the process it consumes a large amount of dissolved oxygen in the water.

       Everyone knows that fish in water also breathe. When the algae break down and consume a lot of dissolved oxygen in the water, the fish are cornered and can only die. Because fish are also organic matter, they decompose just the same. The result is a vicious circle. The algae die and stink, and then the dissolved oxygen goes down, and the fish dies again. The death of the fish leads to a further drop in dissolved oxygen and eventually to total death. So ecologically it's called Dead Zones, and this is what an ecologist has come up with。

       So when you see an algal eutrophication, or you see a green water hyacinth, that's not bad. And then at the end of the day it's going to have a lot of deaths, and one of the consequences of a lot of deaths is you're going to smell all kinds of foul smells.

       We just mentioned that there are two very important elements involved in water eutrophication, one is nitrogen and one is phosphorus. We all know that nitrogen is very important to the human body. What is the most important substance in our life? The protein. The basic molecules of proteins are amino acids. What are the main components of amino acids? Is n。

       We often talk about protein, where does the nitrogen come from? In our agrarian society, also known as the slash-and-burn period, every year after the planting of grain, wheat and rice, they were burned。

       Because the land is hot after burning, while the land is hot, such as a variety of hoes, stones, to crush the ground, and then after burning the grass to form ashes. The ash can go into the soil, which could be a good source of soil for next year's crops.

       Slash-and-burn is actually the burning of land in northeast China. Every spring, the meP always checks how many fires there are in the northeast, Shandong, Jiangsu and Zhejiang provinces. In fact, the burning point is a form of slash-and-burn, which is burning land, but we don't do that anymore. Now if you go to the farm, it's like this. We just grab a handful of fertilizer and throw it into a paddy field.

       The ammonia fertilizer that we use now, or all kinds of ammonia fertilizer in the form of nitrogen, including compost and so on, is thanks to one person. The man's name was Fritz Haber. Fritz Haber was the founder of industrial ammonia synthesis. Without him we wouldn't be here a lot of the time. Why is that? Because the old way of farming couldn't support the planet's huge population.

       Industrial synthesis of ammonia is simply the synthesis of ammonia by nitrogen and hydrogen catalyst at high temperature. This ammonia can be further converted to nitropeptide-ammonia, or some fertilizer for ammonia peptide, and then we can use it directly to fertilize crops, so we don't have to burn waste.

       Fritz Haber won the Nobel Prize in chemistry for this process of industrial synthesis of ammonia. He was A German, but he was also a Jew, so he didn't have a very good life, and he was killed by Hitler.

       Fritz Haber he has another crime that he's often accused of. If you have friends from tohoku, you probably know that tohoku has a Japanese gas bomb. Japanese gas bombs contain a very famous type of mustard gas, which is actually chlorine gas. Who invented chlorine? Fritz Haber also invented it.

       So that's the end of nitrogen, but what about phosphorus? A long time ago we used animal manure to fertilize the soil, and one of the more interesting examples of that time is that there used to be a country in the world that made its money by selling animal manure. That country is next to Australia, called Nauru.

       Nauru is an island nation in the Pacific Ocean. There are a lot of birds in the Pacific, they fly around, they can't fly any more, so you have to find a place to rest, and then the rest place is often chosen as Nauru in the Pacific Ocean, so there is a lot of bird droppings there. Nauru used to be one of the richest countries in the world because of selling bird droppings, but then the droppings sold out, global sea level rose, and Nauru's economic environment is not very good now.

       This is one of the ways that we used to fertilize with phosphorus, and then we went from fertilizing with phosphorus to mining with apatite, which means we don't use animal waste anymore。

       Where does apatite mainly come from? From all kinds of phosphate ore, such as Weng 'an phosphate ore. Weng 'an phosphate mine is one of the largest phosphate mines in Asia, which is located in Guizhou. China's phosphate ore reserves are the second largest in the world, but note that phosphate ore is a non-renewable resource. Because everyone thinks we are a big country of phosphorus, so the phosphate resources are not particularly concerned。

       Including nitrogen fertilizer. Because nitrogen is so cheap right now, a ton of nitrogen doesn't cost a lot of money, so the nitrogen, the phosphorus, that's used in farming, is extremely inefficient. We're only about 20 to 30 percent efficient with phosphorus or nitrogen on the farm.

       We use all kinds of methods to get nitrogen or phosphorus for farming, for growing crops, but in fact we don't value it, we use it very inefficiently. What are the consequences of low utilization efficiency? This leads to all sorts of extra nitrogen and phosphorus, and it gets into the water environment, causing a dramatic deterioration in the water environment.

       為了解釋污水處理廠對于湖泊磷處理到底有沒有效果，我們需要解決以下幾個問題。第一個問題，我們需要問自己，中國湖泊中的污染物的濃度到底是怎么變化的？

       If the concentrations of pollutants like nitrogen and phosphorus in Chinese lakes have increased over the last 10 years, then there is no doubt that sewage treatment plants are ineffective. Because if it worked, it wouldn't increase.

       Second, we need to know how much nitrogen and phosphorus are released into the water by human activities. Third, we need to know which of our anthropogenic activities are responsible for the changes in pollution concentrations in lakes. The fourth step is to determine whether the primary source is related to sewage discharge. Only through the above four steps can we know whether the sewage treatment plant is useful or not. I'm going to go through this a little bit faster, because the academic stuff is really boring.

       Because China has a vast territory and abundant resources, land use types vary greatly, population density varies greatly, and annual precipitation varies greatly. So in the process, we will divide China into several regions, and then look at the changes of pollutants in different regions.

        What is more important in this chart is the change of phosphorus concentration in Lakes in China。

Comparison of total phosphorus concentrations between 2006 and 2014

       And what's interesting about this is that I want you to look at the graph on the bottom, if you look at the graph on the bottom right, there's a light blue line next to it, and that's a trend graph of total phosphorus in all the lakes in Europe.

       Cumulative distribution of total phosphorus concentrations in lakes in China, The United States and Europe

       In addition to the light blue line, look at the red line next to the light blue one. Have you noticed that the red line is very similar to the light blue line? They almost fold together. What's the red line? Is the cumulative distribution curve of total phosphorus concentration in our national lakes in 2014.

       What does this graph mean? This graph suggests that the phosphorus concentrations in our Chinese lakes are actually very, very close to the phosphorus concentrations in European lakes, but they're different from the phosphorus concentrations in the United States. A lot of times we talk about China, whether it's air quality or water quality, we always like to catch up with the UK and the US, we always like to compare ourselves with the US, and now we compare ourselves with Australia.

       But what's interesting is that when we do this comparison, we never think about the population of the United States. There are 350 million people in the United States, and they live in a country about the size of ours. Australia is smaller than us, but its population is only 24 million. But we never compare ourselves with India, which is the closest to us in population. We never bother to compare ourselves with India.

       But in fact, one of the things that you really need to take into account when you're doing this kind of water environment comparison is the effect of population density, and the pollutant concentrations in the lakes are definitely different under different population burdens.

       As I mentioned just now, the natural conditions of pollutants in different regions are different. This chart shows the four regions in China.

       Changes in the historical concentration of pollutants in lakes

      And you can see in the east, in the middle, and in the west, the decrease in phosphorus levels in the lakes was actually quite dramatic, basically from 150 to 200 micrograms per liter to about 50 micrograms per liter now. But it's important to note that 50 micrograms per liter is not a very good value. For example, a better definition for a lake in Europe is a total phosphorus concentration below 25 micrograms per liter, but we're still way above that.

       But in this picture what I want you to see is the green line. If you look at the green line, do you see a slight upward trend in total phosphorus concentrations in the northeast? In fact, we later studied why the northeast didn't fit in with the rest of the world.

       Although the total phosphorus concentration in northeast China is low, it has actually increased in the past few years. Later, we also analyzed that it may be more related to the loss of black soil and agricultural reclamation in northeast China, but we will not study this in detail.

       There are all kinds of human activities that can get nitrogen and phosphorus out of water. It's not just from people, it's not just from our flush toilets, it's from all sorts of sources. For example, free-range farming, large-scale livestock and poultry farming, agricultural mining, etc., may lead to changes in phosphorus concentration in lakes.

       And this is also what happens to phosphorus concentrations in lakes in different regions over time. This is a bit of an effort, but the biggest declines are in rural areas, in urban areas, and in livestock and poultry production, which has declined significantly over the last 10 years.

       After we have this drop we have to figure out what's causing it, what's causing it, so we need to use some linear regression models or large-scale generic models. Since we see that the total phosphorus concentration is mostly decreasing, we need to use a model to determine whether these two are related.

       Finally, we conclude that municipal sewage treatment plants have indeed brought about improvements in water quality over the past 10 years. But as I mentioned earlier, the improvement in water quality is not enough to say that our lake has become a clean state. As you can see right now in Taihu, the cyanobacteria are still erupting because the lake is still not clean.

       One more. Let's go back to the picture. First, we have shown that sewage treatment works. Then we need to go further and say, if we rely on sewage treatment plants, how much reduction potential there is in future urban pollution control.

       We did a final simulation, and we assumed that all of China's urban population was hooked up to a sewage treatment plant, and all of their daily excrement could go to a sewage treatment plant instead of going anywhere else. We also simulate that every village has oxidation ponds, has fancy toilets, so it only has 15 percent of the reduction space.

       So we have shown that wastewater treatment plants can bring down nitrogen and phosphorus as a source of pollution, but the space for further reduction in the future is very limited.

       So the second conclusion is that the potential for upgrading sewage treatment plants in the future is limited, and we need to find another way, because the coverage rate of sewage treatment plants has reached 84%.

       In addition, we have also come to the conclusion that the variation of concentration in water is different in different regions, and its driving force is also different, so we cannot make a one-size-fits-all approach in the process of setting environmental standards and policy making. Now, what do I actually object to now? It is the standard of water environment in China. It is one size fits all.

       What do you mean? For example, the total phosphorus concentration in all of our Lakes in China is basically 200 micrograms per liter. However, have you found a very unreasonable place? For example, the eastern part of China is very densely populated, but no one lives on the Qinghai-Tibet Plateau. So the Qinghai-Tibet Plateau, no matter what, do not do any sewage treatment plant construction, it does not exceed the standard, no matter how, it is the lowest concentration of the place. But t no matter what the eastern region does, it always exceeds the limit.

       In our current environmental standards or policy processes, this one-size-fits-all approach makes no sense, because you have no way of reflecting the impact of population on the local environment.

       There is still a long way to go. What matters is that we are on the right track.

       The article was published in Nature  in 2017; A team. For those of you who are academics, it's a subsidiary of Nature magazine, and it was selected as the cover article of the year, and this is a picture from shaoxing, where I come from. That paper was also the highlight of the month for global environmental science research published by Nature.

       I have just a few minutes, because the academic issues are a little bit more weighty, so Let me give you some of my thoughts on water environmental management or atmospheric management. Those of you who have been to Tibet must know Namtso, one of the three holy lakes in Tibet. Namco is the most popular place to visit among Namco, Yamanaka, and Yamanaka.

       Because Namco is 4,700 meters above sea level, it can barely make it. But if you go to Mapondo, there's definitely a backlash. But Namco, it is at an altitude where most people will not have high reverse, and a few people will have high reverse, so many people are willing to experience it.

       This is a photo from Namtso, and we can see something yellow and green on the photo. What are these yellow green things? It's plastic bags.

       Because there are all kinds of visitors, the annual tourist reception is very large, about tens of thousands of people. Tourists can't take the rubbish away in time, so they have to take it easy there.

       One of my regrets is that we are putting a lot of effort into building sewage treatment plants and treating the lakes that are already polluted, but at the same time we are trying to dirty the lakes that are still relatively clean.

       Two more examples. This is the Yarlung Zangbo River. Look at all the garbage along the river. It's summer time.

      There is another winter, the same way.

       If you look closely, you can see all kinds of rubbish. In fact, we think that environmental pollution is far away from us, that our flush toilet a press, a flush, and we have nothing to do with it. But the problem has not gone far. I think the best way to describe those relatively clear lakes with a sentence of Mayday is not to disturb, not to disturb is the last gentle. Today May Day is still in Beijing for a concert. Because I used to like listening to Mayday.

       In the 1980s, we said that we would never follow the old path of developed countries: pollution first, treatment afterwards. We look down on the United States, we think their economy is at the expense of the environment.

       But by 2017, 37 years later, the phrase had been removed from textbooks. We have no longer said that we should not follow the old path of pollution first and treatment afterwards, because we have already embarked on the path of pollution first and may even have finished it, and we do not know whether we have embarked on the path of treatment afterwards.

       In environmental economics there is a Kuznets curve for the environment, that is, the degree of environmental deterioration varies with the change in per capita income. This income would be a Kuznets inflection point for the environment, after which the environment would improve. Most researchers agree that we should be in the dark before the dawn, or that there are places where the dawn is already breaking, but most places are still dark.

       Finally, I quote a line from Tao Yuanming's "Xi Ci after One's Return" : If you don't expostulation what has gone before, you can catch up with what has come after you. Real lost its not far, feel today is but yesterday. This is what Tao Yuanming said when he went back to his hometown because he could not go on working.

       When we realize that we have made mistakes in the past, we have no chance to correct them now. If you try to correct some mistakes and wonder why you did it in the first place, it is useless, because there is no point.

       What strikes me is that China as a whole is paying great attention to environmental protection. Because yesterday and the day before yesterday, I was talking with a supervisor of chaohu Lake basin and visited them there. He was actually quite a big official.

       By 11:30 p.m. on Friday, he and I were still debating whether Chaohu lake was polluted by internal or external sources. I thought the only people who didn't sleep at 11:30 at night were academic people. Suddenly, I found that officials were still talking about these things at night. Therefore, I think the environment in China is very promising.

       Real lost its not far, feel today is but yesterday. In fact, when we know we've made a mistake, we haven't been too far wrong. Knowing that we did the right thing today is much more important than knowing that we did the wrong thing yesterday.

       Finally, I would like to say that we need to have greater tolerance and patience for environmental governance and environmental improvement. The deterioration of China's water environment and atmospheric environment is by no means a matter of two or three years.

       At present, the public has a very high demand for the protection of their own rights and interests and environmental interests. How high? There is environmental pollution today, and I wish there would be no air pollution tomorrow. For example, today taihu lake so dirty, I suddenly think tomorrow taihu lake if there is no blue-green algae that would be much better.

       But from a rational point of view, this is an unrealistic fantasy. This illusion leads to the fact that the public will report their interests to the government, and the government will be more eager to make some changes and make some explanations. Even before scientific research, it will be involved in a lot of projects.

       In fact, when he was working on a lot of projects, he didn't know whether the project on the road would work or not, because it didn't do the basic research, but it still had to work. Because if it does not work, the people will scold it for inaction. That's a big contradiction.

       Of course, it is right for the public to appeal to environmental protection, but you should adopt a more tolerant and tolerant attitude. So I think if we complain about the environment every day, we should also think, who is responsible for the so-called environmental pollution? All of you in this room, including me. Without us, neither Taihu Lake nor Chaohu Lake would have so much algae.

       Sometimes I think that environmental research is actually the most boring career in the world. For example, if there is environmental pollution in a place, those who carry the pot must be environmental researchers, and it is your poor work that causes environmental pollution.

       But on the other hand, if the place is exceptionally beautiful and beautiful, they will never take credit for it. Born beautiful, it is so good. So sometimes environmental workers are helpless, including our researchers, local government workers, and national decision-making bodies.

      We all know that environmental problems don't happen overnight, but we can't wait for them to happen. How can you pollute for 40 years and expect to see results in 4 years, 4 months, or 4 days? You can't even think about it. I'm kind of calling for a more rational and objective view of environmental issues.

       Suddenly I want to say something about Tianjin University. In fact, Tianjin University is not particularly well known in the south. Especially in this place, I guess the people who have heard of Tianjin University must be very few. In fact, in April and May this year, there was a college association to interview me: Teacher Tong, why did you enter for the examination of Tianjin University?

       I seriously thought about why I applied for Tianjin University after all. When I took the college entrance examination that year, I had similar academic scores with my deskmate, and he actually got similar scores. He might be a few points higher than me.

       That's when I asked him, which school are you applying to? He said I wanted to go north, I wanted to leave my hometown, I wanted to be free. Which school am I talking about? He said Tianjin University. I was particularly impressed by what he said. He said that Tianjin University was the first university in modern China and that low-key luxury had connotations. I say you have a point.

       I applied to Tianjin University. At that time, my first choice was the English Department of Tianjin University. Two months later, I found out that I was transferred to the Environmental Science Department of Tianjin University. Then he went to Finance at Fudan.

       Thank you for your attention。