What is secondary pollution?

The so-called secondary pollution refers to the rust, bacteria and other pollution produced in the process of water pipe transportation after the tap water is treated by the water plant, which is mainly the impurities such as rust in some water pipes and the by-products of chlorination in the water plant.

At present, the water supply of water supply companies can meet the current water quality standards in China, but there is the possibility of water quality decline in the process of delivering water to users. On the one hand, because the water pipeline is easy to age, dirt and impurities enter the pipe network when it is overloaded with supply and maintenance; Water hammer phenomenon causes rust and dirt impurities to fall off from the pipeline and enter the pipe network, and some pollutants will enter the water; On the other hand, there is a phenomenon of secondary water supply in some communities, that is, after the water from the water supply company reaches the community, it first passes through the reservoir and other equipment in the community, and then enters every household, which is always mixed with "uninvited guests" and harmful substances, which is harmful to the health of family members and water-using equipment (washing machines, water heaters, faucets, showers, etc.). The "secondary pollution" of tap water has become an open secret.

concept

Secondary pollution (photochemical smog) refers to the primary pollutants such as hydrocarbons (HC) and nitrogen oxides (nitrogen oxides) discharged into the atmosphere by pollution sources such as automobiles and factories, which react chemically under the action of sunlight to generate secondary pollutants such as ozone (O3), aldehydes, ketones, acids and peroxyacetyl nitrate (PAN). The smog pollution phenomenon formed by the mixture of primary pollutants and secondary pollutants participating in the photochemical reaction process is called photochemical smog.