Verification and modeling of mass transfer in single and multi-element nanofiltration arrays for pilot- and full-scale operation

Productivity and water quality from a 2 MGD nanofiltration (NF) plant were accurately simulated by three NF pilot plants in a four-month field investigation involving simultaneous operation of all systems and various sizes of membrane elements with the same film. This was the first time a full-scale NF facility had been used to develop and verify pilot plant simulation and modeling of full-scale performance. Similar or equal operating conditions (flux, recovery, feed stream) were maintained for all systems. All plants used the same source water, a moderately hard {lcub}(330 mg/L as CaCO3) and highly organic groundwater (11 mg/L nonpurgeable organic carbon (NPDOC), 336 m g/L trihalomethane formation potential (THMFP), 227 m g/L Haloacetic acid formation potential (HAAFP){rcub}. All pilot units were built and operated according to Information Collection Rule (ICR) specifications. The average finished water quality for all membrane plants was 0.4 mg/L NPDOC, 35 m g/L THMFP, 28 m g/L HAAFP. A second order resistance model more accurately described productivity over time than did a zero order direct mass transfer model, although both models produced statistically significant results. Water quality produced by the pilot units were statistically the same for 14 parameters and for practical purposes the same for 15 parameters. Protocols developed from this work were utilized by USEPA for bench- and pilot-scale nanofiltration plant testing.; Newly developed Integrated homogenous solution diffusion models (HSDM) and film theory models (FTM) more accurately predicted full-scale and pilot plant water quality than existing HSDM and FTM models. The newly developed models were integrated with respect to recovery and more accurately represented feed stream concentration than existing models. However, either the integrated and linear average HSDM or FTM models could be used for simulation of nanofiltration processes.; Full-scale plant performance was accurately predicted from single-element or multi-stage pilot plants using the same source, films and varying sized elements. Prediction of permeate water quality was improved by integration of the feed stream concentration with respect to recovery.