The Orange County Water District (OCWD) recently commissioned the
Groundwater Replenishment (GWR) System, an advanced wastewater
treatment facility consisting of microfiltration (MF), followed by reverse osmosis
and advanced oxidation (ultraviolet treatment with hydrogen peroxide).
Developed as an indirect potable reuse facility, the GWR system provides
70mgd of purified wastewater for groundwater recharge and maintenance of an
intrusion barrier to protect the local groundwater basin from seawater infiltration.
Source water to the GWR system consists of secondary municipal effluent
provided by the Orange County Sanitation District (OCSD). Secondary
wastewater is produced by operating two processes, activated sludge (AS)
treatment and trickling filter (TF) treatment.
The GWR System design specifies a blended feed of AS effluent and TF effluent
from OCSD. During GWR System MF feasibility testing, however, only AS
effluent was evaluated. Infrastructure limitations at the time prohibited blending
at the OCWD test facility. While the AS and TF processes produce acceptable
secondary effluent, there are disparities in water quality between the two,
differences that could impact MF performance. The concentration of dissolved
organic constituents and particulate material are generally higher in TF effluent,
when compared to AS effluent. Trickling filters also provide a favorable
environment for snails, which graze on the zoogenic biological slime present on
the TF media. Snails are problematic since they add to the organic and
suspended solid load when sloughed off and carried to the secondary clarifiers.
The snails (and snail shells) could also physically damage the MF membrane
fibers if conveyed to the GWR system. MF membrane integrity would be
compromised, resulting in a host of deleterious affects that reduce effective plant
operations. Given these concerns, TF effluent was not treated during the first 8-
months of operation until further studies were performed. This decision resulted
in the treatment plant being unable to operate at the design capacity, therefore
expediting the need to resolve this issue in a timely manner.
This paper documents the streamlined and innovative pilot testing efforts
undertaken to verify the impact TF effluent would have on the MF treatment
process (and operations of the GWR system). In addition, a variety of water
quality analyses were performed to examine the differences in effluent water
quality between the two secondary treatment processes. Includes figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.1 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 9 |
| Published : | 11/01/2009 |
