This lush hillside is already some distance from the town of Nanwan and two or three kilometers away from the chemical factories in the upper reaches of the Nanwan River.

Zhao Dagang carried more than a dozen wire buckles for catching hares, and carried a half-drunk bottle of Erguotou and half a catty of braised beef in his arms.

In a good mood today, Zhao Dagang plans to find a good place to catch hares all night, no, the dry food is all with him, and he thinks that today is to wait for the rabbit, and he can catch one.

Zhao Dagang took a turn on the hillside, the moon in the sky was very bright, and a hazy path could be seen in the hillside woodland.

In the grass, Zhao Dagang found a trace of being trampled by animals, and according to his previous experience, Zhao Dagang judged that this was a place where hares often haunted.

Set up the wire buckles you brought with you along the messy rabbit path in the grass.

Zhao Dagang was happy in his heart, and found a big tree not far from the wire buckle.

Climbing up the low thick tree, Zhao Dagang was ready to wait for the rabbit.

At that time, it was still the season of late summer and early autumn, and the night was slightly cool, Zhao Dagang, as a bachelor, opened a shop during the day, drank a little wine and caught hares at night, and lived a leisurely life.

Just as he was half-asleep while drinking, Zhao Dagang heard the roar of a machine in the distance.

The sound was getting closer, and the two rays of light were also circling and flickering in the night.

It turned out to be a car!

Zhao Dagang got up from the tree, stood on the thick tree, and saw a water tanker truck driving on the rugged and bumpy mountain road by the hazy moonlight.

It's the middle of the night, where is the water tanker?

Zhao Dagang wondered in his heart, watching the two rays of light get closer and closer, and finally, the water tanker actually got into a forest under the hillside.

That grove was at the foot of the hillside where Zhao Dagang was.

Really curious, Zhao Dagang jumped off the big branch, went down to the bottom of the hillside, and followed the route of the water tanker all the way into the woods.

After walking about half a kilometer in the woods, I found a square concrete fence.

On one side of the wall there were two large iron gates, which were open and a faint light came through.

Zhao Dagang boldly approached the iron gate, and saw through the crack in the door that a water tanker was pouring waste water into a large pool in the middle of the courtyard.

The courtyard is large and square, surrounded by a cement wall, and there are many open spaces around it, except for a large pond in the center.

The light in the yard was very dim, but I could vaguely see a lot of weeds around the empty yard.

Looking at the appearance of the water tanker truck, it is seven or eight percent new, and there is no mark on the water tank, not even a license plate.

Zhao Dagang wanted to continue watching, but the pale green wastewater in the tanker had been dumped, and the driver got in the car and was ready to drive the car out.

Zhao Dagang hurriedly withdrew from the gate and hid far away in the woods.

The water tanker exited the yard, and the driver got out of the car and locked the big black iron gate before driving away along the same road.

After the water tanker left, Zhao Dagang returned to the big iron gate, looking through the crack in the door, it was dark, there was no light, there was no figure, and only a circular pool in the center could be vaguely seen in the hazy moonlight.

The cement wall around the yard is more than two meters high, and without tools, it is impossible to climb into it.

At that time, Zhao Dagang felt that the whole thing was strange, but he didn't know what was going on, and with the mentality that more things were better than less, Zhao Dagang did not track down the secrets in the yard, but continued to go back and wait for the rabbit.

It wasn't until three months later, when the town of South Bay began to develop strange illnesses, the government found that it was mercury poisoning, and rumors that the groundwater was contaminated, that he remembered that it might have something to do with the small compound hidden in the woods on the hillside.

Now that he met Nan Zhiqiao and Zhen Zhen, the two undercover investigators, Zhao Dagang was happy to lead the way, and on the way, he told everything he knew.

After telling his story, Zhao Dagang asked Nan Zhiqiao: "I have long heard that some factories will use underground sewage to treat wastewater, will the sewage discharge into the ground definitely pollute the groundwater in Nanwan Town?"

Zhao Dagang regarded Nan Zhiqiao as an expert and asked about his worries.

Nan Zhiqiao replied professionally: "Actually, there are many kinds of underground sewage discharge, and not every way will cause groundwater pollution. ”

Zhao Dagang exclaimed: "Will there be pollution from underground sewage?"

"Well, there is a way of underground sewage discharge called high-pressure deep well sewage, also known as deep well injection, which is to inject waste liquid into permeable underground rock formations through deep wells under a certain pressure, these deep wells are often thousands of meters deep, and the upper part has a thicker aquifer of oil and gas goaf wells, which can prevent waste liquid from polluting groundwater, and can store waste liquid in deep rock formations. ”

"There is also this technology, but what I have seen on the Internet is that underground sewage will cause groundwater pollution. Zhao Dagang felt that what Nan Zhiqiao said was very different from the comments he saw on the Internet.

"Deep well perfusion, as a way of underground sewage discharge, has high technical requirements, first of all, the depth of the deep well to reach thousands of meters, which is technically difficult, there are pressure requirements when perfusion, accidentally will cause waste liquid leakage or small earthquakes, such accidents have occurred in the United States, and China's current deep well perfusion technology has not been widely used. The pollution caused by underground sewage discharge you just mentioned should refer to the other two ways of underground sewage discharge, seepage pit seepage well sewage discharge and karst cave sewage discharge. ”

"Is there any difference between the sewage discharge of this seepage pit and the deep well injection?"

"There is a big difference, the sewage discharge from seepage pits and seepage wells is similar to the ancient people's treatment of domestic sewage and feces, which is to dig a big pit or a well, pour wastewater directly into the pit, and let the wastewater slowly seep into the ground, so that the harmful substances in the wastewater seep into the groundwater, causing pollution.

The karst cave sewage is mainly in the south, because there are many karst landforms in the south, and there are many karst caves, and some enterprises directly discharge untreated wastewater into the karst caves, and the karst caves are mostly extended in all directions, and many are connected with underground rivers, which causes pollution of the surrounding water quality. ”

"So that's the case, that mysterious courtyard in the forest can't be a deep well for irrigation, right? But if it's a serious sewage method, why do they have to sneak around, send waste water over in the middle of the night, there's no need. Zhao Dagang muttered in confusion.

Ye Zhenzhen interjected and asked: "Is there any obvious sign around that yard, if it is a regular deep well infusion, there will be obvious marking." ”

Zhao Dagang shook his head, "No, it's just an inconspicuous small courtyard, hidden in the woods, it's difficult for outsiders to find out, and when you get there, you can see it with your own eyes." ”

——

The off-road vehicle turned left and right in the mountainous area of the upper reaches of the Nam Van River, and finally entered a hillside forest under the guidance of Zhao Dagang.

There was a track of a big car in the forest, and Nan Zhiqiao drove an off-road vehicle and followed the track of the big car.

Soon, a concrete wall appeared in the woods.