Application of biofiltration as a promising pre-treatment method to enhance the sustainability of low-pressure membrane operations
Final Report Abstract
The overall goal of this proposed project was to determine the optimal operational and backwash procedures for this promising technology as a pre-treatment to enhance the sustainability of low-pressure membrane operations (i.e. potentially reduce the frequency of backwashing of the BACCs, reduce frequency of membrane chemical cleaning intervals, etc.). Assessment of the BACCs for membrane pre-treatment was optimized under the range of seasonal conditions experienced in Lake Ontario (i.e. feed water quality, temperature, etc.) and compared with a 'conventional' membrane pre-treatment method (coagulation and flocculation). The full-scale BACCs at the Lakeview WTP was operated and optimized over a period of 2.5 years, to allow for time the proposed projects to be accommodated within everyday operational constraints/demands. To deal with conditions which cannot be attempted in a fullscale operating drinking WTP, membrane pilot-plant was operated following select full-scale BACCs. The final project component included a comparison and evaluation of UF membrane performance at the adjacent full-scale Lakeview and Lome Park WTPs in Peel Region, taking into account the presence and/or absence of pretreatment. At one point during this study, ozonation was out of service, and this presented an opportunity to compare ozone on/off scenarios and their effect of BAC filtration and UF processes in terms of biopolymer removal. Given the importance of biopolymers for fouling, this fraction was quantified using a chromatographic technique. The study performed at a full range of temperatures between 3 and 23 °C showed that temperature affected biopolymer and DOC concentrations in raw water (Lake Ontario). Biopolymer and DOC concentrations increased with increasing temperature. Unexpectedly, BAC filtration without prior ozone resulted in higher biopolymer removal than with ozone. It was evident that a wide range of EBCT between 4 and 19 min only had a positive effect on biopolymer removal through BAC filtration when ozone was out of service. Ozone pre-treatment was observed to positively impact active biomass in BACCs. However, since an increase of active biomass did not result in higher biopolymer removal, the active biomass concentration cannot be surrogate for biofiltration performance through BAC filtration. However, ozone-free operation resulted in higher deposition of biopolymers on a UF membrane and its slight deterioration in performance. The comparison of the performance of the conventional and advanced processes with regard to biopolymer removal at two full-scale drinking WTP showed that conventional processes seemed to be a better pre-treatment option for UF membranes compared to advanced processes. The plants were fed with the same surface water source, however, they differed in configuration and type of coagulants used. Overall, this research demonstrated the importance of NOM quantification and control as it pertained to its adverse impact on many treatment processes. It was also observed that aluminum sulfate slighdy outperformed PACl for biopolymer removal when both were dosed at an average concentration of 0.36 ± 0.08 mg Al/L. As a result of my initial work, the Region of Peel, Canada provided additional funding that permitted follow-up research.
Publications
- Pretreatment impacts on biopolymers in adjacent ultrafiltration plants. JAWWA Vol 106 Issue 9, September 2014, Pages E372-E382
Siembida-Lösch, B.; Anderson, W.B.; Bonsteel, J.; & Huck, P.M.
(See online at https://doi.org/10.5942/jawwa.2014.106.0080) - Effect of ozone on biopolymers in biofiltration and ultrafiltration processes. Water Research Volume 70, 1 March 2015, Pages 224-234
Siembida-Lösch, B.; Anderson, W.B.; Wang, Y. M., Bonsteel, J.; & Huck, P.M.
(See online at https://doi.org/10.1016/j.watres.2014.11.047) - 2014. Biopolymer removal in full-scale conventional and advanced drinking water treatment trains at two large adjacent plants. Desalination and Water Treatment 57 (47), 22277-22289, 2016
Siembida-Lösch, B.; Anderson, W.B.; Bonsteel, J.; & Huck, P.M.
(See online at https://doi.org/10.1080/19443994.2016.1140595) - Biopolymer removal in full-scale conventional and advanced drinking water treatment trains at two large adjacent plants, Desalination and Water Treatment, 57:47, 22277-22289, 2016
Siembida-Lösch, B.; Anderson, W.B.; Bonsteel, J.; & Huck, P.M.
(See online at https://doi.org/10.1080/19443994.2016.1140595)
