Design of ro plant pdf

Need an account? Click here to sign up. Download Free PDF. Control system design of reverse osmosis plants by using advanced optimization techniques Desalination and Water Treatment, Adrian Gambier.

A short summary of this paper. Control system design of reverse osmosis plants by using advanced optimization techniques. Desalination and Water Treatment 10 — October www. All rights reserved. The standard approach considers two control loops with PI controllers.

This is an economical viable solution for the control problem. However, the resulting control performance is normally suboptimal because controllers are in- dividually tuned assuming inaccurately that the system is decoupled. In order to overcome this problem, some advanced control algorithms have been proposed in the specialized literature. For plants originally built using only ion exchange, adding RO can reduce chemical regeneration requirements by a factor of 20 or more.

Complete removal of regenerable systems might even be considered. With RO upstream removing the bulk of the dissolved salts, the polishing ion exchange systems might be economically replaced with service demineralizer beds that are chemically regenerated by an offsite water service company, or they might be replaced by electrodeionization EDI.

EDI units use electricity to continuously regenerate their ion exchange resins. Some new and existing plants are now required to remove dissolved salts from wastewater streams prior to discharge.

A well-performing RO system can make it possible to re-use the water within the plant. The concentrated salt stream remaining after RO treatment can then be more economically hauled to an area better able to handle it environmentally, or it could be evaporated or discarded in some other manner. The political and regulatory advantages of becoming a zero-liquid discharge ZLD facility can offset part of the capital and operating costs.

But the superior economics of RO operation are only achievable if the system and its upstream treatment components are correctly designed, operated, and maintained. Pulling a water sample for laboratory analysis is a good start in preparing an RO design Table 1. A comprehensive analysis provides data on the metals in the water, such as iron, manganese, and aluminum; the dissolved salts cations and anions ; the water pH acidity ; and possibly the inorganic total suspended solids TSS.

A measurement of the total organic carbon TOC often correlates with the potential for biological activity. A TSS analysis reveals the concentration of filterable solids in the water. The concentration of dissolved metals in the water, such as iron, changes in the sample as they react with oxygen introduced by contact with air.

This causes some of the metals to oxidize and become insoluble. The metals that remain suspended may cause the TSS value to increase significantly with many well-water sources. Biological fouling solids are not well-represented in TSS results. The mass of these solids typically becomes negligible when the TSS filter is dried prior to weighing for results.

The water could be tested for its silt density index SDI if the metals are first separated out of the sample. This test is highly sensitive to the ability of biological solids to coat and reduce the flow rate through its 0. Its results correlate with the fouling tendencies of a membrane system. No analysis is perfect, and water quality can change over time.

Even the characteristics of a well-water source can change if the well is relatively shallow. Sampling methods also affect results; some concentrations can change between sample pull and analysis. Ammonia and carbon dioxide CO 2 may degas or CO 2 may dissolve from exposure to air. Any of these changes will cause the water pH to change.

An accurate water pH is best measured on-site. Chemical suppliers can use a water analysis to predict how much purified water permeate the RO might safely separate from the source before the dissolved salts become too concentrated in the remaining water and form scale within the membrane elements Table 2.

The water analysis is also used in designing the RO system, both in projecting the purified water quality and in assessing any effect of the salts on system hydraulics. An RO system and its pretreatment equipment designed solely on one water analysis may not be fully optimized for the fouling characteristics of the source. It might be oversized or, of greater concern, it might not be ideal for water that has a high membrane-fouling potential. This can best be determined with a pilot study.

A well-designed pilot study uses components that have been scaled down but still offer the same type of media, and use similar flow velocities and exposure times.

The pilot RO Figure 1 should duplicate the permeate recovery, the permeate flux rate that is, the permeate flow per unit of membrane area , and concentrate stream vessel exit velocities, along with the scale inhibitor dosage and shutdown flush methods.