Microfiltration (MF) membranes were used in a nonbiological application during a demonstration
scale study performed at Orange County Sanitation District's (OCSD) Plant 2 to treat effluent
from an advanced primary treatment process. The MF unit was operated for two years from
January 2002 through January 2004 using 0.2 µm polypropylene hollow fiber membranes. The
primary objective of this work was to test the technical and economic feasibility of treating
primary effluent (average TSS = 58 mg/L) directly using membranes, to produce an effluent
suitable for direct discharge to the ocean. Such a nonbiological option for treatment of primary
effluent is particularly important to OCSD since the high quality effluent produced by
microfiltration could allow the District to use the shorter of their two ocean outfalls. Currently, the
shorter outfall is permitted only for emergency discharges because it discharges closer to the
shoreline and would require a significantly higher quality effluent. Regular use of the "short"
ocean outfall could save the District millions of dollars by delaying the need to build another
deep-water outfall.
During the two years of operation, excellent quality effluent was consistently produced by the
MF with average TSS and turbidity values of 2.7 mg/L and less than 3 NTU, respectively. Fecal
and total coliform concentrations were reduced by between 3 to 4 logs. For the first nine months
of testing, average chemical cleaning intervals of about 3 to 4 days were observed. An apparent
decline in the normalized chemical cleaning interval was observed during some intermediate
periods of testing. This is possibly attributed to changes in the operation of the full-scale primary
treatment at OCSD, and isolated instances of functional problems with the Clean-In-Place (CIP)
heating system of the demonstration unit. The cleaning interval was restored later in the
investigation.
This paper presents the results of the testing performed from October 2002 through January
2004. During this period, several changes were made in the operating conditions to optimize
operation based on the changing influent quality. Lower fluxes and backwash cleaning intervals,
and alternative feed types were tested. Several autopsies were also performed on the fibers at
regular intervals to determine the condition of the fibers with respect to membrane fouling to
help assess a reasonable membrane life for such an application. No signs of irreversible
degradation were observed. The results show that nonbiological treatment of primary effluent
with MF membranes is technically achievable and produces effluent that could be discharged to
the ocean or used as feed water for a final stage of treatment before reuse.
Includes 3 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 400 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 03/01/2005 |
