🔍 Key Concepts

• Reverse osmosis (RO) flow paths: series vs parallel piping of membrane modules • Effect of pressure and recovery on product water quantity vs quality • How fouling typically occurs in spiral‑wound RO membranes

💭 Think About

• Think about what happens to pressure and driving force for RO when you put modules one after another in series. Does that mainly affect how much water you can push through, or how clean it is? • If you take two identical RO modules and feed them with the same seawater in parallel, what happens to the flow rate and what happens to the salt rejection in each module? • How does running brine (concentrated reject) into the next module in series affect salt concentration at that second module’s inlet and the risk of fouling?

✅ Before You Answer

• Clarify in your mind whether series piping mainly increases recovery (throughput) or salt rejection (purity) for RO systems. • Remember that parallel piping gives each module the same feed quality and pressure—check how that affects purity vs total output. • Consider that fouling risk usually increases with higher concentration and longer flow path; ask whether series flow makes that better or worse.