Street sweepers spray water to help clear away a variety of debris and dust from streets and roadways. This can include  leaves, dirt, pebbles,  and other materials that have been tracked onto the street. The spraying of water helps to soften up the debris to make  it easier to sweep away. Additionally,  water helps to prevent dust from becoming airborne and helps to keep the air clean for nearby residents and businesses.

The use of street sweepers is beneficial for several reasons. First,  it helps to keep the streets and roadways looking clean and presentable,  which is beneficial for people who live and work in an area where street sweeping occurs. It also helps to keep dust and  debris from entering homes or businesses, which can lead to potential health risks. Lastly,  it ensures that water and other natural resources are not wasted due to the accumulation of debris and dust on the  streets.

In conclusion,  street sweepers play a vital role in helping to keep cities and towns clean by spraying water and sweeping away debris.  This helps to ensure that the air is clean and that the streets remain presentable and well maintained.