Buildings generate different types of contaminants including solids, sludge, sediment, floating debris, oil, detergents, pool and spa chemicals, pesticides, herbicides, and scum. These contaminants should be collected and removed to prevent them from reaching public utilities. In many communities, there are two separate and independent drainage systems; one for wastewater collection – a sewer system that carries sewage from buildings and a second independent system for rainwater, or storm water. The storm water is often sent directly to the sea, lakes, artificial lagoons or rivers, if they exist, while domestic sewage is transported to wastewater treatment plants, for treatment to remove pathogens and other contaminants.