An oil-water separator comprising: an oil-water main feeding an oil-water manifold having a first distribution branch feeding a first oil separation chamber, and a second distribution branch feeding a second oil separation chamber, the oil separation chambers (19, 20) each individually comprising as components: (i) upper and lower portions relative to horizontal joined through side walls and defining a substantially sealed enclosure for containing a fluid therein; (ii) an oil-water inlet located in a lower portion of the chamber and receiving a distribution branch from the oil-water main to define an oil-water flow path from the oil-water main into the chamber; (iii) a water outlet located in a lower portion of the chamber and defining a water flow path from inside to outside the chamber; (iv) an oil outlet located in an upper portion of the chamber and defining an oil flow path from inside to outside the chamber; (v) an air inlet located in an upper portion of the chamber and defining an air flow path from outside to inside the chamber; and (vi) a valve system comprising valves in fluid communication with and regulating the flow paths of the oil-water inlet, the water outlet, the oil outlet, and the air inlet, the valve system having first and second valve settings, the first valve setting (a) to open the oil-water flow path of the oil-water inlet and the oil flow path of the oil outlet, and to close the air flow path of the air inlet and the water flow path of the water outlet, and the second valve setting (b) to close the oil-water flow path of the oil-water inlet and the oil flow path of the oil outlet, and to open the air flow path of the air inlet and the water flow path of the water outlet; and a valve control system to alternate opposing valve settings (a) and (b) between the first and second oil separation chambers (19, 20). an oil-water main feeding an oil-water manifold having a first distribution branch feeding a first oil separation chamber, and a second distribution branch feeding a second oil separation chamber, the oil separation chambers (19, 20) each individually comprising as components: (i) upper and lower portions relative to horizontal joined through side walls and defining a substantially sealed enclosure for containing a fluid therein; (ii) an oil-water inlet located in a lower portion of the chamber and receiving a distribution branch from the oil-water main to define an oil-water flow path from the oil-water main into the chamber; (iii) a water outlet located in a lower portion of the chamber and defining a water flow path from inside to outside the chamber; (iv) an oil outlet located in an upper portion of the chamber and defining an oil flow path from inside to outside the chamber; (v) an air inlet located in an upper portion of the chamber and defining an air flow path from outside to inside the chamber; and (vi) a valve system comprising valves in fluid communication with and regulating the flow paths of the oil-water inlet, the water outlet, the oil outlet, and the air inlet, the valve system having first and second valve settings, the first valve setting (a) to open the oil-water flow path of the oil-water inlet and the oil flow path of the oil outlet, and to close the air flow path of the air inlet and the water flow path of the water outlet, and the second valve setting (b) to close the oil-water flow path of the oil-water inlet and the oil flow path of the oil outlet, and to open the air flow path of the air inlet and the water flow path of the water outlet; and (i) upper and lower portions relative to horizontal joined through side walls and defining a substantially sealed enclosure for containing a fluid therein; (ii) an oil-water inlet located in a lower portion of the chamber and receiving a distribution branch from the oil-water main to define an oil-water flow path from the oil-water main into the chamber; (iii) a water outlet located in a lower portion of the chamber and defining a water flow path from inside to outside the chamber; (iv) an oil outlet located in an upper portion of the chamber and defining an oil flow path from inside to outside the chamber; (v) an air inlet located in an upper portion of the chamber and defining an air flow path from outside to inside the chamber; and (vi) a valve system comprising valves in fluid communication with and regulating the flow paths of the oil-water inlet, the water outlet, the oil outlet, and the air inlet, the valve system having first and second valve settings, the first valve setting (a) to open the oil-water flow path of the oil-water inlet and the oil flow path of the oil outlet, and to close the air flow path of the air inlet and the water flow path of the water outlet, and the second valve setting (b) to close the oil-water flow path of the oil-water inlet and the oil flow path of the oil outlet, and to open the air flow path of the air inlet and the water flow path of the water outlet; and the first valve setting (a) to open the oil-water flow path of the oil-water inlet and the oil flow path of the oil outlet, and to close the air flow path of the air inlet and the water flow path of the water outlet, and the second valve setting (b) to close the oil-water flow path of the oil-water inlet and the oil flow path of the oil outlet, and to open the air flow path of the air inlet and the water flow path of the water outlet; and a valve control system to alternate opposing valve settings (a) and (b) between the first and second oil separation chambers (19, 20).