Knowledge of the principles, methods, and tools employed in the general operation of engines, pumps, valves, motors, and related equipment; general maintenance work; safe work practices; principles and methods of biological and chemical sewage analyses; effects and problems of industrial waste in water/wastewater treatment processes; and principles of supervision. The work areas may be indoors or outdoors and have loud noise, active machinery, high-pressure fluid systems, electrical equipment, confined spaces, heights and depths, fumes, airborne particles, noxious gases, and chemicals.