DSD has approximately 2,000 staff, consisting of 1,850 permanent establishment and 150 contract posts. There are about 300 professional staff, 1,100 technical and general staff, and 600 frontline staff and direct labours. The department is divided into four branches - Projects and Development, Operations and Maintenance, Electrical and Mechanical, and Sewage Services. Each branch is headed by an Assistant Director. There are seven integrated management system under ISO 9001 and ISO 14001 to cover all aspects of DSD.

The Deputy Director chairs a Green Management Committee to formulate and review the environmental policies and environmental goals of the department. The Committee also monitors the performance of environmental targets and promotes staff awareness and involvement in protecting the environment. The Committee is represented by the Management Representative or Deputy Management Representatives of each Integrated Management System under which the environmental policies are implemented and monitored. A green manager at the Assistant Director level with assistance from a senior professional and the department administration oversees and coordinates the day-to-day green issues.