New Membrane and GAC Treatment Plant for TOC
RemovalAWWA California-Nevada Section
Brian Shoener
Provost & Pritchard Consulting Group
Fresno, California
October 2, 2013
Background Two Water Sources
Reservoir Gravity feed to plant
Bad water quality
River Pumped to plant – Two
1000 HP pumps
Good water quality
Background Existing Treatment Plant
500 gpm (0.72 MGD)
Sedimentation basin No sludge removal
Two dual media pressure filters
Chlorine gas
1 MG storage tank Gravity feeds most of
system
Problem River
Excellent water quality
But………
River flow must be above a certain rate
Pumping is expensive
Bacteriological concerns at low flow
Problem Plant cannot meet DBPs
and turbidity
THMs > 120
HAA5 > 180
Did pre-chlorinate –stopped due to DBPs
But… now causing manganese problems and biological growth in basins
Alternatives Additional TOC Removal &
DBP Reduction
Ion Exchange – Piloted for 2 weeks. Worked
Brine handling and disposal issues
Chloramines Not feasible. Complexity.
Distribution system – wells using chlorine
Public acceptance problems
Alternatives Additional TOC Removal &
DBP Reduction
Granular Activated Carbon Easy to operate
Helps taste and odor
Solution Clarifier, membrane and
GAC
How to build upgrades and keep plant operating?
Build clarifier and feed existing filters
Fill in existing ponds
Construct building for membranes and GAC
Solution Client wants to bid
three different membrane vendors
Design for largest membrane system
Ability to run all or a portion of flow thru GAC
Lesson Learned All vendors have
different:
Skid sizes
Inlet/outlet
orientations
Waste drains
Air compressors
Lesson Learned Chosen vendor would
not move feed pumps off skid.
Next vendor supplied inaccurate design drawings
Planned Operation 3 Modes
Normal – Thru clarifier and pumped to membranes
Bypass Pumped –Bypass clarifier and pumped to membranes
Bypass Gravity –Bypass clarifier and directly feed membranes
Startup Issues New membranes have air
assisted backwash draining. This affects:
Backwash every 30 minutes
CIP every 30 days
MW every 30 days
Causes high velocity discharge
Overwhelmed gravity drains
Startup Issues Variable pressure from
reservoir and flow restrictions due to influent pipe size
Limited flow to 560 gpm from reservoir
Caused issues with backwash return
Bypass gravity mode cannot provide enough flow to feed one skid and backwash the other
Acceptance Test First start up attempt
Worked through many alarms
Second attempt
Vendor replaced some valving
Completely redid vendor supplied program
Everything worked
Operational Results Clarifier alone with
existing filters produced excellent TOC results.
TOC Removal
5 mg/L raw water
3.5 mg/L after clarifier
1 mg/L after membranes
ND after GAC