Sewage generated from people's lives flows through the sewer to the public sewage treatment plant for centralized treatment. Today we visited Dihua Sewage Treatment Plant, which is the largest secondary sewage treatment plant inTaiwan, with capacity of up to 500,000 cubic meters.

Sewage treatment is usually divided into three stages: the primary treatment is to remove the precipitable substances in the wastewater through filtration and sedimentation procedures; the secondary treatment is to use biological methods to remove the organic matter in the wastewater through trickling filtration, aeration, and disinfection procedures. The compounds are decomposed into inorganic substances; the tertiary treatment is to remove toxins and metals through activated carbon and microalgae organisms respectively. After the secondary treatment, the water can be used for secondary use.

In the Treatment Plant, we saw that the wastewater going from a state of raw sewage that was full of vomit dirty, passing through layers of checkpoints, and transforming into the reusable water that can be put back to the river or be used for irrigation. The sludge filtered out in the process can also be used as a raw material after the drying and pressing procedures.

We walked this whole afternoon, but it was only a small part of the whole sewage treatment. I can't help but feel that it takes so much time to purify the wastewater, but polluting it only takes one second.