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usc Refereed/Peer-reviewed The application of fixed bed high rate nitrifying trickling filters (NTFs) for the removal of track organic chemicals of concern (CoC) is less well known than their application to nutrient removal in water treatment. Particularly, the effect of exogenous organic carbon substrate (sucrose) loading on the performance of NTFs is not well understood. A laboratory-scale NTF system was operated in recirculation mode, with the objective of removing ammonia and CoC simultaneously. The efficiency of a high rate NTF for removal both of low concentration of ammonia (5 mg NH4-N L-1) and different concentrations of CoC in the presence of an exogenous organic carbon substrate (30 mg total organic carbon (TOC) L-1) was investigated. In the presence of exogenous organic carbon, the results demonstrated that the high rate NTF was able to successfully remove most of the CoCs investigated, with the removal ranging from 20.2% to 87.54%. High removal efficiencies were observed for acetaminophen (87.54%), bisphenol A (86.60%), trimethoprim (86.24%) and 17α-ethynylestradiol (80.60%). It was followed by the medium removal efficiency for N, N-diethyl-m-toluamide (61.31%) and atrazine (56.90%). In contrast, the removal of caffeine (28.43%) and benzotriazole (20.20%) was poorer in the presence of exogenous organic carbon. The removal efficiency for CoC was also compared with the results obtained in our previous study in the absence of exogenous organic carbon. The results showed that the addition of exogenous organic carbon was able to improve the removal of some of the CoC. Significant TOC percentage removals (45.68%-84.43%) and ammonia removal rate (mean value of 0.44 mg NH4-N L-1 h-1) were also achieved in this study. The findings from this study provide valuable information for optimising the efficiency of high rate NTF for the removal of ammonia, CoC and TOC.

Cadmium (Cd) is of no known essential biological function and is toxic to plants and animals. Leaching of Cd through soil profiles has implications for both its accumulation in subsoil or contamination of ground-water. We measured adsorption and transport of Cd in the presence of Ca and Na salts of varying ionic strengths using batch and miscible displacement techniques. Two variable charge soils, an Oxisol and an Alfisol, were used in this study. The Alfisol, despite its lower clay content, showed an adsorption coefficient ( K ) that was four times higher than the clay-rich Oxisol. Such a difference in adsorption was attributed to the presence of 2 : 1 layer silicate minerals in the Alfisol and the consequent high surface negative charge density. In column experiments, a marked effect of ionic strength on the breakthrough curves (BTCs) of Cd was observed when the concentrations of NaNO 3 were increased from 0.03 M to 0.15 M in the background solutions. This increase caused nearly four times faster movement of Cd through the Oxisol soil column. The effect of increasing Ca(NO 3 ) 2 concentration on Cd adsorption and transport was relatively less pronounced than that recorded for the NaNO 3 solution. In the Alfisol, the increase in Ca(NO 3 ) 2 ionic strength from 0.05 M to 0.25 M resulted in four-fold smaller adsorption coefficient. For both soils, the movement of Cd at a constant ionic strength was, however, an order of magnitude faster in the presence of Ca(NO 3 ) 2 than that in the presence of NaNO 3 . To describe the combined effect of ionic strength and pH, we used the K values calculated from the BTCs with CXTFIT model to develop a simple theoretical relationship between Cd adsorption and [H + ], [Ca 2+ ] and [Cd 2+ ] in solution. The relation was found to be consistent with other published studies. The study demonstrated that Cd mobility in soils is strongly affected by the soil solution composition (ionic strength and type of cations).

Pharmaceuticals released into aquatic systems are expected to sorb to sediments to varying degrees. Their sorption is likely to influence their fate and, ultimately, the risk they pose to aquatic organisms. This has led to the European Medicines Agency requiring an assessment of affinity to solids, using batch sorption methods, for the environmental risk assessment (ERA) of new human medicines. However, a large body of data is generated before pharmaceuticals are released onto the market, including their extent of distribution throughout the human body, measured by the volume of distribution (VD). In the present study, batch sorption experiments were undertaken using 12 different soils and sediments to determine whether VD was a good indicator of experimental Kd values for 21 pharmaceuticals. The r2 values obtained from the regressions ranged from 0.39 to 0.76 (with a median value of 0.5) and all regressions were found to be significant. The use of this more comprehensive set of soils and sediments was consistent with previous studies comparing VD and Kd, despite the Kd values of the selected pharmaceuticals varying greatly between soils. The relationship between Kd and VD was greatly improved when zwitterionic antibiotics and carbamazepine were not included, possibly due to complex sorption or pharmacokinetic behavior. There are likely to be a number of factors affecting the sorption of pharmaceuticals that cannot be explained by VD. However, further work may elucidate how these factors can be accounted for, enabling VD to be effectively used to facilitate the ERA of human pharmaceuticals with already available information. Refereed/Peer-reviewed