Comparison of NF-RO and RO-NF for the Treatment of Mature Landfill Leachates: A Guide for Landfill Operators

Abstract

Reverse osmosis (RO) and nanofiltration (NF) are among the state-of-the-art technologies for treating landfill leachates. Due to the complexity and variance in the composition of leachates, numerous combinations of multiple technologies are used for their treatment. One process chain for the treatment of raw leachate is RO followed by further concentration of RO-retentate using NF (RO-NF scheme). The aptness of this process train used by some landfill sites around the world (usually with the aim of volume reduction so as to re-inject the concentrate into the landfill) is questionable. This study investigated two schemes RO-NF and NF-RO (nanofiltration of raw leachate followed by reverse osmosis of NF permeate) to identify their merits/demerits. Experiments were conducted in bench scale using commercial membranes: DOW Filmtec NF270 and SW30HR. Filtration trials were performed at different pressures to compare the water and solute transports in the individual stages of the two schemes. Based on the water fluxes and compositions of retentates and permeates; osmotic pressures, energy demands, and other possible operational advantages were discussed. NF-RO offers some advantages and flexibility for leachate treatment besides being energy efficient compared to RO-NF, wherein osmotic pressure steadily increases during operation in turn increasing operation and maintenance costs.

Polyvinyl alcohol‐based membranes for filtration of aqueous solutions: A comprehensive review

“…[ 241 ] On the other side, nanofiltration (NF) and reverse osmosis (RO) operate at much higher pressure ranges. [ 242 ] While NF is effective for removal of ions and organic compounds, RO is mainly applicable for desalination of brackish water. [ 243 ] Forward osmosis (FO) process is also favored while such operational conditions similar to UF are applied.…”

Recent technologies for leachate treatment: a review

“…Over the past two decades, membranes have become increasingly popular in industrial technologies where reliable and repeatable purification or concentration is required (Dolar et al 2016). Membrane filtration is a very suitable process for removing and reducing different pollutants such as organic and inorganic matter, microorganisms, and trace metals (Ramaswami et al 2018). According to the literature, there are four types of membrane methods: nanofiltration, ultrafiltration, microfiltration, and reverse osmosis (Anand and Singh 2014;Rathnayake and Herath 2018).…”

“…In RO, any solvent that contains metal cations is passed through a membrane in such a way that the metal concentrations are removed. RO can be used for the removal of trace metals, suspended/colloidal materials, and dissolved solids from landfill leachate (Ramaswami et al 2018). Talalaj (2015 pointed out the high removal rates of different pollutants from intermediate leachate with the use of reverse osmosis.…”

Reverse osmosis treatment system for landfill leachate: Operation conditions, advantages and challenges

“…RO process was studied for treatment of landfill leachate within two decades from its discovery and was reported to be the most effective method for treating leachates [9][10][11][12][13][14]. By the mid-1980s, RO systems had already penetrated significantly into the market of leachate treatment [15]. However, RO concentrate is difficult to deal, the specific energy consumption of RO process is much higher than other treatments and it is difficult to struggle with significant scaling problems.…”