Efficient phosphorus removal from MBR effluent with heated aluminum oxide particles (HAOPs).

Biological processes and chemical precipitation in combination with polishing by granular media or membrane filtration can remove 90-95% of the phosphorus (P) from wastewater. However, reducing the concentration to levels near those in high-quality receiving waters requires additional advanced treatment, typically including adsorption onto specialty media. These processes are often costly, they can be hard to control when the P loading varies, and their effectiveness can be compromised by the presence of competing adsorbates in the water.

Insights and Model for Understanding Natural Organic Matter Adsorption onto Mixed Adsorbents.

Adsorption-based processes are commonly used to remove natural organic matter (NOM) from drinking water sources and thereby mitigate its impacts on other water treatment processes and the quality of the finished water. These processes are complicated by the fact that NOM comprises multiple fractions that can exhibit disparate adsorption behaviors. Prior modeling of NOM adsorption has invariably focused on systems with a single adsorbent, but results presented here demonstrate surprising and counterintuitive behavior in systems containing two or more adsorbents.

A multi-spectral approach to differentiate the effects of adsorbent pretreatments on the characteristics of NOM and membrane fouling.

Pretreatment of feed water is widely applied to mitigate NOM-induced fouling of low-pressure membranes. This research investigated the effectiveness of two pretreatment modes for NOM removal by heated aluminum oxide particles (HAOPs) and the associated reductions in membrane fouling and trihalomethane (THM) formation potential. One mode, referred to here as pre-adsorption, is the conventional process in which adsorbent particles are added to and thoroughly mixed with the feed, after which the particles are separated from the water either upstream of or by the membrane.

NOM fractionation and fouling of low-pressure membranes in microgranular adsorptive filtration.

Membrane fouling by natural organic matter (NOM) was investigated in microgranular adsorptive filtration (μGAF) systems, in which a thin layer of adsorbent is predeposited on low-pressure membranes. The adsorbents tested included heated aluminum oxide particles (HAOPs), ion exchange (IX) resin, and powdered activated carbon (PAC). Size exclusion chromatography (SEC) separated the NOM into four apparent MW fractions with significant UV₂₅₄.

New conceptualization and solution approach for the ideal adsorbed solution theory (IAST).

Despite the widespread use of the ideal adsorbed solution theory (IAST) to predict competitive adsorption of hydrophobic organic compounds from aqueous solutions, the underlying principles of the model are not widely understood. A new conceptualization is presented that treats the adsorbed phase as gas-like with a total surface pressure equal to the sum of the partial surface pressures of the adsorbed species. In this conceptualization, the key assumption of the IAST is reformulated as indicating that the partial surface pressure exerted by an adsorbate depends only on its adsorption density and a surface activity coefficient that depends on the total surface pressure.

Simultaneous removal of phosphorus and foulants in a hybrid coagulation/membrane filtration system.

At many wastewater treatment plants, chemical addition is required to meet the requirements for discharge of phosphorus. Membrane filtration is an attractive option for removing the chemically precipitated phosphorus, but that process can be impeded by fouling of the membrane by effluent organic matter (EfOM). In the current study, membrane fouling and ortho-P removal were explored in hybrid adsorbent/membrane systems dosed with alum and/or a new aluminum-based adsorbent (heated aluminum oxide particles, HAOPs).

Examination of NOM chlorination reactions by conventional and stop-flow differential absorbance spectroscopy.

Mechanisms of chlorination of natural organic matter (NOM) in surface water (Lake Washington) were explored via differential spectroscopy. Two types of differential spectra (overall and incremental) were generated for this water chlorinated at pH 7 using varying chlorine doses and reaction times. The differential spectra contain two kinetically and spectroscopically distinct components.

Reactions of the flavonoid hesperetin with chlorine: a spectroscopic study of the reaction pathways.

The flavonoid hesperetin (Hsp) contains aromatic rings substituted with hydroxyl and methoxyl groups, which activate it toward electrophilic attack and hence make it a potential surrogate for natural organic matter with respect to reactions with chlorine. This paper describes the chlorination pathway of Hsp, based on a combination of electrospray tandem mass spectrometry (MS/MS) and absorbance spectroscopy. When a solution containing Hsp is dosed with NaOCl at pH 7, chlorine substitution into Hsp occurs exclusively into the meta-dihydroxy substituted ring.

Fouling and natural organic matter removal in adsorbent/membrane systems for drinking water treatment.

Adsorbent particles added to ultrafiltration (UF) systems treating drinking water can remove natural organic matter (NOM) and some other contaminants from the water, but their effect on membrane fouling is inconsistent-in some cases, fouling is reduced, and in others, it is exacerbated. This research investigated the behavior of UF systems to which powdered activated carbon (PAC), heated iron oxide particles (HIOPs), or (nonadsorbent) SiO2 particles were added. On a mass basis, the PAC removed the most NOM from solution, the HIOPs removed less, and the SiO2 removed essentially none.

Correlations between differential absorbance and the formation of individual DBPs.

This study examined correlations between the differential absorbance at 272nm (deltaA272) and the formation of disinfection by-products (DBPs) in chlorinated water from the Tolt River, a water source for Seattle, WA. The DBPs investigated included chloroform (CHCl3), dichlorobromomethane (CHCl2Br), mono-, di- and trichloroacetic acids (MCAA, DCAA, and TCAA, respectively), chloral hydrate (CH), dichloroacetonitrile (DCAN) and 1,1,1-trichloropropanone (TCP). Whereas the kinetics of DBP formation are complex and are non-linear, the same DBP data represented as a function of deltaA272 are quite simple.

The relationship between TOX formation and spectral changes accompanying chlorination of pre-concentrated or fractionated NOM.

The change in the absorbance upon chlorination (the differential absorbance, AA) of natural organic matter (NOM) that has been concentrated, isolated, and/or fractionated from five sources was explored as a possible indicator of the formation of total organic halogen (TOX) in the samples. The results demonstrate that concentration and isolation of NOM using techniques that are currently in widespread use does not significantly alter the TOX-deltaA272 relationship that applies to the unprocessed NOM. However, when such samples are fractionated, the TOX-deltaA272 relationships for the different fractions are not identical.

Modeling the mass-action expression for bidentate adsorption.

The number of bidentate binding sites on a pristine surface (i.e., sites comprising two adjacent monodentate sites plus the space between them) can be substantially larger than the maximum number of bidentate molecules that can adsorb to the surface.