Erren River was at the junction of Tainan and Kaohsiung. Due to the heavy use of acidic chemical solvents and the discharge of untreated waste water from metal factories, it was the most heavily polluted river in the world 30 years ago (it was really one of the most polluted rivers in the world at that time).

We met a resident there who still had an clear memory about how it was heavily polluted. The government made an improvement so what we saw was just fine. But the resident said that nearby factories still secretly discharged waste water on weekends or on rainy days. This could not be discovered immediately, but we found some abandoned wires on the side. And when we arrived the lower river, we saw an unbelievable sight. The river in front of us was full of plants that we almost mistakenly thought it was a grassland. Palm-sized duckweed covered the entire water surface. It also reminded us of the factory wastewater mentioned by the resident. But since usually the eutrophication caused by household and livestock wastewaterthe, it was less likely caused by the factories. Is there any other water pollution here? We don't dare to say easily.

In fact, during this trip, we did see some clues that this water area was seriously polluted, but also it was continuously improved. The changes made with hard work may not be perfect, but everyone is continuing to work hard.