International Journal of Environmental Science and Technology
Fig. 1 Experimental setup of three-stage RO Plant. The raw water is pumped through filters and doses of biocide, antiscal- ant, and sulfuric acid are added before it is introduced in the RO tank
Results and discussion
Table 1 Specification and characterization of RO plant Product
BW30–400
Benchmar k ing of RO p l ant without acid treatment
Part number
98,650
E ff ect of pressure of RO plant at di ff erent stages with time
Active area ft 2 (m 2 )
400 (37)
Feed spacer thickness (mil) Permeate flow rate gpd (m 3 /d) Stabilized salt rejection (%) Minimum salt rejection (%)
28
Figure 2 shows an increase of pressures at all the stages of RO plant rapidly with the passage of time as compared to expected pressures. The RO plant was operated at 75% recovery, and the trend of increase in pressures was found to be very rapid, which was caused by fouling and scaling of membrane abruptly. This, in turn, resulted in an increase in cleaning frequency. Repeated cleaning of RO membranes increased to TDS which caused a decline in salt rejection. The first-stage pressure of RO increased from 8.8 to 10.6 bar having a pressure drop of 1.8 bar and increased linearly. Similarly, the second- and third-stage pressures were also increased. Figure 2 describes the increase of pressure due to cake formation on the membrane surface and in the first stage almost 20% increase in pressure was observed while in sec- ond, third stage, and total reject increase of pressures was found to be 23%, 30%, and 44% of initial values, respec- tively, over 2 months. In the second and third stages, the increase in pressures was relatively higher as compared to the first stage. Feed water had a high concentration of salts
10,500 (40)
99.50%
99%
Membrane type
Polyamide thin- film composite
Max operating temperature Max operating pressure
113 F( 45 C)
600 psig ( 41 bar)
Max pressure drop
15 psig (1 bar)
pH range, continuous operation pH range, short-term cleaning
2–11 1–13
19 m 3 /hr
Max feed flow
Max feed silt density index Free chlorine tolerance
5
<0.1 ppm
the meter of HANNA (model # HI 83,141, HI 8734) was used. LSI factors (calcium hardness and alkalinity) were calculated by the titration method in the lab.
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