The Optimal Operation and Maintenance Process in Reverse Osmosis System for Water Reclamation
Date Issued
2010
Date
2010
Author(s)
Huang, Cheng-Yu
Abstract
The objective of the present study is to monitor the fouling of reverse osmosis (RO) membrane system in terms of economic analysis by optimization of pretreatment, operation flux rate and frequency of membrane cleaning, and also to achieve the RO permeate water quality to match the Singapore NEWater quality standards.
Two types of membranes processes microfiltration (MF) and ultrafiltration (UF) were used for pretreatment before RO filtration at various operating fluxes. The performances of MF and UF processes were monitored in terms of flux recovery and the over all process pretreatment including RO filtration performance was monitored with energy consumption.
The RO treatment with MF was carried out at initial operating fluxes of 10, 15 and 20 LMH with an intermittent chemical cleaning for every 6 hr. Results show that a good recovery of about 96 % normalized flux after chemical cleaning was achieved. The energy consumption calculations for only RO membrane filtration after the MF pretreatment at an initial flux of 10 LMH is 68.5 kWh/m3. In comparison the energy consumption for RO filtration after MF pretreatment at low operating flux (10 LMH) is 1.38 and 1.81 times lower than the energy consumptions at operating fluxes of 15 and 20 LMH respectively.
In the case of RO system with UF, the pretreatment was carried out with initial operating fluxes of 10 and 20 LMH followed with an intermittent chemical cleaning for every 12 hr. Excellent recovery of 96-100 % was achieved. The energy consumption for only RO membrane filtration after the MF pretreatment at an initial flux of 10 LMH is calculated as 80.5 kWh/m3 and is 1.58 times lower than 20 LMH flux.
The energy consumption comparison of whole process of RO filtration including MF and UF pretreatments by taking in to consideration of frequency of chemical cleaning shows that the process involving UF pretreatment results an energy consumption of 69 % with that of MF process.
Further the RO permeate quality in terms of turbidity, NO3--N, NH4+-N, conductivity, total dissolved solids (TDS) and total organic carbon (TOC) matches with the Singapore NEWater quality standards, but the pH values of RO permeate was 4.82-7.41 that is lower than the standard values 7.0-8.5.
In conclusion, from the energy consumption in achieving high quality standards of permeate, the RO system with a pretreatment of UF membrane is suggestible in the reclamation of water.
Subjects
RO membrane
fouling
pretreatment
operation flux
CIP
water reuse
SDGs
Type
thesis
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