How Rain Affects Wastewater Treatment

A big plant that cleans water, called an aerobic granular sludge (AGS) plant, is really good at taking out nutrients and organic stuff. But what about tiny pollutants, like medicine and chemicals? That's what scientists wanted to find out. They looked at 19 medicines and 2 industrial chemicals in this plant over a year. They checked how well the plant cleaned these pollutants in both dry and rainy weather. When it's dry, the plant did a good job. It took out more than 20% of 14 different pollutants. Some of these pollutants stuck to the sludge, which is like a thick layer of bacteria and dirt that helps clean the water. But when it rained, things changed. The rain made the water dirtier with some pollutants, but the plant's cleaning power went down. It removed less of these pollutants, and some even ended up in the cleaned water. The scientists found that when it rains, the plant has less time to clean the water. This made it harder for the plant to break down some pollutants. But for others that stick to stuff, the rain didn't make much difference. The plant did better than regular plants in dry weather, but in rainy weather, it's hard to say which does better. This study is the first to look at how rain affects these plants, showing that rain can make it harder for the plant to clean water.