small concrete dam separates the wastewater treatment facility oxydation ponds

aerating aeration america area bay california cleaning concrete contaminated control corrosion dam drop equipment facility filtering filtration francisco gate green industrial industry lake metal nobody outdoor outdoors oxydation plant pollutant polluted pollution pond ponds pump pumps quality recycled release replenishment reservoir river san separates service sewage shoreline silicon small states sunny sunnyvale system treatment united usa valley waste wastewater water working