Scaling Risk Assessment in Nanofiltration of Mine Waters.

Krzysztof Mitko,Krzysztof Piotrowski,Ewa Laskowska,Marian Turek,Piotr Dydo

doi:10.3390/membranes10100288

Krzysztof Mitko, Krzysztof Piotrowski + Show 3 more

Open Access

https://doi.org/10.3390/membranes10100288

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Abstract

Nanofiltration can be applied for the treatment of mine waters. One of the main problems is the risk of crystallization of sparingly soluble salts on the membrane surface (scaling). In this work, a series of batch-mode nanofiltration experiments of the mine waters was performed in a dead-end Sterlitech® HP 4750X Stirred Cell. Based on the laboratory results, the concentration profiles of individual ions along the membrane length in a single-pass industrial-scale nanofiltration (NF) unit was calculated, assuming the tanks-in-series flow model inside the membrane module. These calculations also propose a method for estimating the maximum achievable recovery before the occurrence of the calcium sulfate dihydrate scaling in a single-pass NF 40″ length spiral wound module, simultaneously allowing metastable supersaturation of calcium sulfate dihydrate. The performance of three membrane types (NF270, NFX, NFDL) has been evaluated for the nanofiltration of mine water.

Highlights

Nanofiltration (NF) and reverse osmosis (RO) are widely used for water and wastewater treatment.Nanofiltration, due to its high rejection of all ions except the monovalent ones, is widely used to eliminate the groundwater hardness [1] or to recover important substances, such as proteins and sugars.NF may be considered as an alternative to RO for desalination of brackish waters, where SO4 2− is the prevailing anion [2]
The dead-end experiments showed that the nanofiltration process may be safely operated even at 80% recovery of permeate
A method of predicting the operational limits of nanofiltration modules working in high scaling risk situations, e.g., when the feed water is rich in calcium and sulfate, was proposed

Summary

Introduction

Nanofiltration (NF) and reverse osmosis (RO) are widely used for water and wastewater treatment.Nanofiltration, due to its high rejection of all ions except the monovalent ones, is widely used to eliminate the groundwater hardness [1] or to recover important substances, such as proteins and sugars.NF may be considered as an alternative to RO for desalination of brackish waters, where SO4 2− is the prevailing anion [2]. Nanofiltration (NF) and reverse osmosis (RO) are widely used for water and wastewater treatment. Nanofiltration is used as a pretreatment [3] before other methods, such as reverse osmosis, as well as for the treatment of various mine waters, including acidic mine waters [4,5], discharge from oil sand mining [6], saline waters from the mining industry [7]. Scaling leads to significant degradation of membrane performance, shortening of membrane lifetime, decrease in permeate quality, increase in the energy consumption as higher pressure difference is necessary, increased cleaning frequency, higher consumption of antiscalants, and in the worst cases, irreversible membrane degradation. Antiscalant treatment and/or pH adjustment are usually used as the feed water pretreatment methods to decrease the mineral scale formation [12,13].

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