For big buildings, we need big cooling capacities. Central air-conditioning systems using chillers are used. Chilled water is most convenient way to collect heat from indoor spaces. We just need pipes. Miles and miles of them.

Chilled water from chillers is about 44 degree Fahrenheit (about 7 deg C). In order for room heat to be transfered to water efficiently, air in room is circulated through tubes containing flowing chilled water.

That is main function of air handling unit in a central air-conditioning chilled water system.

Another function of an air handling unit is to clean air. It does this by filtration.

A most basic air handling unit, or AHU, contains a fan, a cooling coil, and an air filter enclosed in a box-like structure.

Have you heard of belts used for removing water from sludge?

Yes, there is a type of equipment used in wastewater treatment that uses belts to remove water from sludge. It's called a belt press.

This is how it works:

There are two continuously running belts made of woven polyester material in belt press. There are many freely rotating rollers where belts pass over.

The belts are typically about 2 feet wide, depending on design. There is an upper belt, and a lower belt. The arrangement of belts and their travel on rollers is made in such a way that at some point along route, they will be placed tightly against one another. The pressing together of these belts squeezes out water from sludge.