Treatment of the Cyanotoxin Anatoxin-a via Activated Carbon Adsorption

Stringent water quality regulations and general
aesthetic issues have urged drinking water industry to apply
advanced water treatment technologies that can meet multiple
treatment objectives. Removal of significant amount of natural
organic matter (NOM), including colour causing organics, to meet
stringent disinfection by product (DBP) regulations from source
water with low alkalinity and low turbidity is very challenging
with conventional water treatment processes. Membrane filtration
processes are effective in removing significant amount of NOM thus
minimizing the formation of carcinogenic DBPs. However, fouling of
membrane is a major problem affecting system performance. Improved
pretreatment of feed water helps reduce or eliminate membrane
fouling. This study characterized source water, examined fouling in
nanofiltration (NF) membranes and explored various pretreatment
options to reduce NF fouling. Resin fractionation was performed to
characterize NOM and to identify the major fractions responsible
for DBP formation in natural source water of the Tatamagouche water
treatment plant (WTP) in Nova Scotia. The source water primarily
comprised of hydrophilic neutrals (HIN) and hydrophobic acid (HOA)
compounds, with the latter being a major contributor to the DBP
formation. Fouling behaviour of the NF membranes was examined at
bench- and full-scale levels to understand the impact of source
water quality on membrane fouling in the Tatamagouche and Collins
Park WTPs. Bench- and full-scale results revealed higher fouling in
the Collins Park WTP which together supported ongoing membrane
cleaning practices in the plant. Surface enhanced Raman
spectroscopy (SERS), demonstrated here as a novel technique,
suggested that carbohydrates and proteins are the main foulants in
the source water. Bench-scale experiments conducted to evaluate the
performance of ozone (O3), ultraviolet (UV), hydrogen peroxide plus
ozone (H2O2/O3), H2O2 plus UV (H2O2/UV) and O3 plus UV (O3/UV) for
reducing NOM and DBP precursors suggested that the O3/UV AOP offers
the optimum reduction of NOM. Integrating AOP pretreatments with NF
membrane resulted in an improved permeate flux but not permeate
quality of the NF membrane.

Advanced oxidation processes: assessment of natural organic matter removal and integration with membrane processes

This study investigated the nanofiltration (NF) fouling behavior by two surface waters that serve as source waters for full-scale integrated membrane systems (IMS) of the Tatamagouche and Collins Park drinking water treatment plants (WTPs) in Nova Scotia, Canada. Bench-scale NF fouling experiments conducted under controlled laboratory conditions showed a flux decline of 25% with the Collins Park source water compared with a flux decline of 15% with the Tatamagouche source water over 96 hours of operation. The higher rate of flux decline observed was related to the water quality parameters observed in the Collins Park source water. Membrane autopsies were conducted on virgin and fouled membranes using different techniques to compare the fouling propensity of the two feed waters. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed considerable difference between the fouled membranes fed with two source waters. Analyses of full-scale NF fouling data from the two IMS plants reveal higher fouling in the Collins Park WTP. Full- and bench-scale NF fouling observations provide consistent results that together support ongoing membrane cleaning practices in the Collins Park WTP.

Integrating bench- and full-scale nanofiltration testing for two surface waters

Anatoxin-a adsorption by virgin and preloaded granular activated carbon

Specification and sizing of the separation processes with membranes always require experimentation, headed by classification of the processes intended to be developed The usual dimensional classification only considers the separation processes with membranes as mechanical unit operation, where the only involved transport phenomena is to pass or not through the cutoff diameter of the membrane porous A more comprehensive classification method defines the different separation processes with membranes by several operating parameters such as level of feed pressure, driving forces, membrane material, type of modules, and involved transport phenomena and application, allowing more precise experimentation The proposed classification method for separation processes with membrane was successfully developed at the industry, allowing a more objective experimental work, achieving consequently better data for implementing the project

Separation processes with (bio)membranes: Overview and new phenomenological classification

This study investigated the fouling of four polyamide nanofiltration membranes by two surface waters that differed substantially in major properties. The emphasis was on determining the characteristics of the fouling layer on the membranes. The rates of fouling for the two waters differed considerably, with a more rapid flux decline being observed for the water having higher biopolymer and major ion concentrations. Measurements of membrane roughness, contact angle and zeta potential in general showed considerable differences for each of these properties among the virgin membranes. However, values of each of these parameters tended to converge for all membranes after fouling, regardless of which water had been used. This result is very significant (for example for the removal of trace contaminants, which in many cases may depend on membrane properties) because in practice a membrane spends virtually all of its operating life fouled to some degree. Several techniques including transmission electron microscopy (TEM) were used to conduct detailed investigations of the fouling layer. These results demonstrated the great heterogeneity within that layer, despite the similar overall properties mentioned above. This heterogeneity is significant for quantitative understanding of the relationship between fouling and flux and for strategies to reduce or remove fouling.

Investigating the fouling layer of polyamide nanofiltration membranes treating two different natural waters: internal heterogeneity yet converging surface properties

G. G. Leppard

Papers

Investigating the fouling layer of polyamide nanofiltration membranes treating two different natural waters: internal heterogeneity yet converging surface properties