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460 J. Qin and K.A. Kekre
Fig. 10.14. Online TOC of RO permeate from ASP-MF-RO and MBR-RO processes vs. time (33).
compared in Table 10.18. General speaking, rejections of the RO membrane for all components
were similar in both the ASP-MF-RO and the MBR-RO processes although the quality
of both RO feeds fluctuated. For the parameters involved in biological process, NH 4–N and
NO3 in RO permeate from the MBR-RO process were 0.05–0.22 and 0.53–1.92 mg/L,
respectively, which were lower than those (NH4–N 0.07–0.42 mg/L and NO3 1.62–3.86
mg/L) from the ASP-MF-RO process. It could be attributed to better performance of MBR
than ASP on the reduction of the biodegradable components, including TOC mentioned
above. pH (5.0 in average) of the MBR-RO permeate appeared lower than that (5.5 in
average) of ASP-MF-RO permeate although pHs of their RO feeds were similar. However,
for other inorganic ions, the quality in both permeates were similar since the same RO
membranes were used.
In summary, the new MBR-RO process could produce same or more consistent quality (in
terms of TOC, NH4, and NO3) of RO permeate compared to the conventional ASP-MF-RO
process. The RO permeates with the lower TOC level from the new MBR-RO process than
the ASP-MF-RO process more greatly benefits the special application where the reclaimed
water from municipal wastewater is to supply for the electronics industry to further produce
ultrapure water since ultrapure water with low TOC contamination is required.
6.4. Conclusions
The conclusions from the study can be summarized as follows.
1. The new MBR-RO process demonstrated the capability of producing the same or better (in terms
of TOC, NH 4, and NO 3) product quality compared to the conventional ASP-MF-RO process in the
reclamation of domestic sewage.