Canal Control for T&O

Elevated T&O levels (> 10 ng/L) at the head of a canal system can be attributed to 2 factors.  First, T&O compounds were produced in the reservoirs, released downstream, and present at the head of the canal system.  Second, during rainfall events pulses of T&O compounds lasting 3 to 14 days have been observed.  These pulses are due to (1) increased nutrient stimulation of algae and fungi within the river canal, and/or (2) solubilization and transport of T&O compounds from irrigated soils into the river system.

“Hot spots” for T&O compound production in canals have been observed and linked to periphytic algae (attached to canal lining and base of canal).  “Hot spots” have been identified in both faster- and slower- water velocity sections of the canals.  T&O production has generally occurred over a 1 to 3 mile section of the canal.  Urban and agricultural return flows can contain elevated T&O levels, or nutrient levels that could stimulate in-canal T&O production, and should be monitored if they are observed to be flowing during sampling events.

Treatment Options (see below for more details):

• Reduce nitrate input into canal from groundwater pumping
• Mechanically remove periphytic (attached) algae from canal walls
• Apply liquid-biocides to canal water
• Apply fixed-biocides to canal walls during canal dry-up
• Shift finished water production to WTP with lower T&O levels

Reduce nitrate input into canal from groundwater pumping
Mechanically remove periphytic (attached) algae from canal walls
Apply liquid-biocides to canal water
Apply fixed-biocides to canal walls during canal dry-up
Shift finished water production to WTP with lower T&O levels