CITY OF LOS ANGELES
DEPARTMENT OF PUBLIC WORKS

Technical Corner

Maintenance and Operations

Maintenance personnel at Tillman perform scheduled and corrective maintenance on thousands of pieces of manual and computer-controlled equipment. The work is carried out by 39 skilled staff members. The spectrum of work ranges from tasks as simple as changing light bulbs to replacing 1200 horsepower motors.

Plant operations staff consists of 22 people who are responsible for taking readings, monitoring operations, making adjustments to equipment, and conducting preventive maintenance. Staff is on duty 24 hours a day to ensure that the plant functions properly.

Maintenance and operations staffs join teams, participate in workshops, and go on retreats that are designed to encourage feedback on how to improve the plant’s efficiency and effectiveness. Staff and management collaboration have resulted in significant cost savings for the City and its ratepayers.

Budget Information:

Nitrification/Denitrification

The Los Angeles Regional Water Quality Control Board required the City of Los Angeles to implement a Nitrification/Denitrification treatment system at the L.A.  –  Glendale and D.C. Tillman Water Reclamation Plants. The limitation of nitrogen reduces ammonia and nitrite contaminants to aquatic organisms, nitrate levels for humans, and helps prevent eutrophication (algae blooms and fish kills) in lakes and rivers. As a result, the City is currently spending $60 million at Tillman and $20 million at L.A. - Glendale to comply with these new permit limits for nitrogen.

Nitrification is an aerobic process, converting ammonia (NH4) into nitrite (NO2) and nitrate (NO3). Nitrification also requires 2 to 2.5 times more oxygen (or air) than the standard secondary treatment process. Denitrification converts nitrate back into nitrite and then into nitrogen (N2) gas. A different set of bacteria is used in the Denitrification process then those used in Nitrification. As a result, the forms of nitrogen in wastewater are converted into nitrogen gas (79% of the earth’s atmosphere is N2 gas).

The $80 million in plant modifications to the plants for the NdeN process include replacing the RAS piping system with larger diameter pipe, increasing the pumping capabilities of the return activated sludge system and recycled wastewaters, and upgrading the air distribution system with more and larger air lines, adding additional air compressors, and installing more air diffusers in the aeration tanks. Also, major modifications are being made to the electrical, and instrumentation and controls systems.