Understanding and Control of Biopolymer Fouling in Ultrafiltration of Different Water Types

Xing Zheng,Hendrik Paar,Martin Jekel,Stephan Plume,Mathias Ernst,Frederik Zietzschmann,Zi Wang

doi:10.3390/w9040298

Abstract

The present work focuses on understanding and control of biopolymer fouling in ultrafiltration of a typical surface water and nearby secondary effluent for direct and indirect portable use. Characterization results show that both kinds of biopolymers are of similar molecular weight. Longer than one year water quality monitoring results show that the C/N ratio in the secondary effluent biopolymers was relatively constant at around 4.8, while that in the surface water macromolecules fluctuated at around 6.9. Under a similar mass load, the investigated secondary effluent biopolymers lead to hydraulic resistance slightly higher than that caused by filtering surface water macromolecules; however, the correspondingly formed fouling is significantly less reversible by hydraulic backwashing. The quantity of the nitrogenous biopolymers in the secondary effluent demonstrated a strong correlation with the extent of the irreversible fouling in ultrafiltration (UF), while that from the surface water did not. In membrane fouling cleaning tests, certain detergent demonstrated high efficiency in removing the irreversible fouling after UF of the secondary effluent, but presented no effect in eliminating fouling caused by the surface water foulants. In-line coagulation using FeCl3 prior to UF was shown as an effective fouling control method, but the effect depends heavily on the type of feed water.

Highlights

Ultrafiltration (UF) membranes have often been used in filtering surface water or treated domestic wastewater for direct and indirect portable use, e.g., as pretreatment prior to RO (Reverse Osmosis) in water purification or reclamation
During water quality monitoring period (February 2009–August 2010, except winter 2009 for surface water (SW)), these two types of water demonstrated similar pH and calcium content (Table 2), even during rainfall event. This indicates that the secondary effluent (SE) and SW deliver similar water chemistry condition, which builds up fair situation in comparing fouling because both parameters are critical factors affecting the severity of organic fouling [21,27]
The present study investigated the character of organic constituents in the range of biopolymer substances in two types of typical water sources, and compared their fouling behavior and controlling effects during the UF process

Summary

Introduction

Ultrafiltration (UF) membranes have often been used in filtering surface water or treated domestic wastewater for direct and indirect portable use, e.g., as pretreatment prior to RO (Reverse Osmosis) in water purification or reclamation. To select suitable fouling control strategies such as pre-treatment, chemical cleaning, etc., identification and characterization of primary foulants is necessarily required [1]. Previous studies show that biopolymers (macromolecular protein-like substances and polysaccharides) are primary organic foulants in low pressure membrane filtration of both secondary effluent (SE) [2,3] and surface water (SW) [4,5]. Water 2017, 9, 298 effluent organic matter (EfOM). They are mostly solvable microbiological products (SMP) secreted by microorganisms during metabolism and/or related to extracellular polymeric substances (EPS) [6,7,8]

Methods

Results

Conclusion