International Journal of Environmental Science and Technology
value in total reject water stream more than 2.5, resulted in fouling and scaling in membrane and pressures of all stages got higher subsequently. In order to control the LSI value, sulfuric acid had been dosed in the feed line and main- tained pH up to 7.2 or 7.3. Ultimately, the LSI value was obtained < 1.5. Hence, by controlling of LSI value, fouling and scaling of RO-Membranes were optimized. Therefore, instead of a change of pH of feed water, alternate options are available that we can change temperature, calcium hardness, and total dissolved solids of feed water in order to reduce fouling and scaling in the RO membrane. Water consumption is increasing day by day as the avail- ability of clean water is shortened. The RO is the heart of the desalination process. Therefore, it is necessary to enhance the life of RO plants. Further research is required in this field due to its severity. In two-stage RO, fouling and scal- ing trends are to a smaller extent as compared to three-stage plant due to less concentrations of salts in the reject stream. Thus, the LSI value will be < 1.5 in the total reject of two- stage RO and ultimately fouling and scaling will be con- trolled. Hence, it is an alternate solution of optimization of fouling and scaling on RO membranes to change its design.
Fig. 10 Normalized concentration of salt in reject water versus time. The concentration of only Chloride remains the same and the concen- tration of every chemical increases over time in the rejected water
(Kucera 2015). The LSI value was found to be below 1.5 at the third stage in Fig. 3, meaning some scale formation occurred but still was at acceptable levels. Washing of mem- brane was minimized; hence, the quality of membrane for salt rejection can be preserved. This study was focused on RO plant utilization, and dif- ferent parameters related to the efficiency and operational analysis of parameters inlet and outlet of total dissolved solids, flow rates, LSI factor and thus the same meaningful results were concluded. As shown in results that designed RO three-stage plant in which first stage feed was rejected as a feed to second stage, and second stage was rejected to the feed of third stage. It was concluded that feed of the third stage of RO contained higher TDS, hardness in terms of CaCO 3 , and total alkalinity. In the third stage, membrane load seemed to be higher than the other two stages. Due to the presence of higher salt concentration, the membrane fouling and scaling were seen. It was concluded that the rapid increase in pressure of all stages is due to membrane fouling and scaling in the RO plant. Hence, the LSI value depends on various factors (temperature, pH, TDS, calcium hardness, and total alkalinity) which can be controlled by changing these parameters. In this research, pH value was adjusted by the addition of H 2 SO 4 to control LSI and to avoid rapid fouling and scaling on the surface of membranes. It was obvious that under acidic condition, CaCO 3 was dissolved and reduction in alkalinity minimized the effect of pressure; fouling and scaling were controlled, which resulted in normalization of cleaning frequency. Keeping in view the results; pressures, flow rate, and LSI value changed after acid treatment in all stages of the RO plant. Three-stage RO unit with high LSI
Conclusion
In the current paper, the reverse osmosis (RO) technology is used to improve the water treatment processing of a paper manufacturing plant. The same process can be applied to improve water processing in every industry where water is used. To study the improvements in the treatment of raw water, a before and after method was used to see how the RO and the chemical used have improved the processing of the raw water. There is a significant improvement in both the processing and efficiency of the raw water. The process increased the amount of the treated water which is obtained at the output and decreased the rejected outflow which is waste. The improved water flow caused increase in scaling at the RO membrane which decreased the overall efficiency of the process. The addition of acid improves the efficiency of the water treatment process while also maintaining the quality of the water obtained in the product flow.
Acknowledgments The authors wish to thank all who assisted in con- ducting this work.
Comp l iance with ethica l standards
Conflict of interest The authors declare no conflict of interest.
Open Access This article is licensed under a Creative Commons Attri- bution 4.0 International License, which permits use, sharing, adapta- tion, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source,
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