A recent pilot study was conducted in two phases in 2007 using a ceramic microfiltration
membrane. The goals of the study were to consistently treat turbidity to levels below 0.05 NTU
and DOC to levels less than 4 mg/L. The study was performed on various water sources that
will ultimately contribute to the full scale reservoir estimated for completion in 2010. The ceramic
membrane system used during this study consisted of a single monolithic element with 269
square feet of membrane surface area. The pilot setup included a rapid mix tank with a 20
minute retention time that was directly fed to the ceramic membrane. Additional tests were
performed with in-line coagulation with a retention time of 30 seconds. During the entire study
no form of solids settling was utilized. The flux rates operated during Phase I reflected 90 gfd
with one (1) hour filtration cycles. In Phase II the flux rates were lowered to 75 gfd with 30
minute filtration cycles to address the higher solids loading contributed by the powdered activated carbon (PAC) slurry. The
influent water tested during the study included a surface water source, a secondary effluent
reservoir and a combination of the two sources. Turbidity ranged between 2 to 300 NTU in the
surface water and less than 15 NTU in the secondary effluent source. Organic concentrations
(TOC) ranged between 7 and 14 mg/L which averaged greater than 93 percent in the form of dissolved organic carbon
(DOC). Specific ultraviolet absorption (SUVA) measurements were performed during the study
and reflected values consistently less than 2 L/mg-m. Phase I test consisted of enhanced
coagulation with a pH less than 6 and various forms of aluminum and iron salts. The optimum
coagulant was determined to be ferric chloride with a dose range between 60 and 100 mg/L.
This combination achieved the turbidity goals and provided a maximum DOC removal of 52.6
percent. In addition, PAC doses up to 80 mg/L were added directly to the membrane which
provided an additional 14.2 percent removal. The second phase was performed with enhanced
coagulation and a PAC slurry concentration of 4,000 mg/L that was fed to the membrane. The
results associated with this setup provided a maximum DOC removal of 91.8 percent producing
a final filtrate with DOC levels less than 1 mg/L. The membrane achieved the set goals under
various testing conditions and was able to recover transmembrane pressures equivalent to a
new membrane after every clean in place (CIP) regardless of the testing parameters. The
ceramic microfiltration system proved it could provide a single step solution without pretreatment
in addressing waters with difficult TOC removal demands. This level of treatment could be
realized in various forms including enhanced coagulation, PAC addition, PAC slurry, direct
injection, or various combinations of the techniques tested. Includes 2 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.1 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 8 |
| Published : | 11/01/2008 |
