Project Engineer in a water treatment plant manages the execution of projects related to water treatment, from planning to handover, ensuring compliance with standards and regulations. They are responsible for project delivery on time and within budget, while also ensuring the highest quality and safety standards.

Service Technician in a water treatment plant's field job is responsible for the maintenance, repair, and troubleshooting of water treatment systems, ensuring optimal performance and compliance with regulations. This includes performing routine inspections, water quality testing, and system adjustments. They also handle emergency repairs, document service activities, and may provide training to clients on operation and maintenance.