Source and drinking water organic and total iodine and correlation with water quality parameters.

Iodinated disinfection by-products (I-DBPs) have recently emerged as part of the pool of DBPs of public health concern. Due to limitations in measuring individual I-DBPs in a water sample, the surrogate measure of total organic iodine (TOI) is often used to account for the sum of all I-DBPs. In this study, TOI and total iodine (TI) are quantified in raw and treated waters in treatment trains at three sites in the Northeast United States. The occurrence, magnitude, and seasonality of these species was investigated within each sampling train and across the different sites. A regression model was developed to explore how TOI occurrence varies with routinely measured physical and chemical parameters in a water sample. The TOI and TI concentration at the three sites ranged from below the method detection limit to 18 µg/L and from 3 and 18.9 µg/L, respectively. There was substantial inter-monthly variability in TOI without a clear seasonal signal, and the concentration of TOI did not increase upon treatment. The results of the multivariate regression model showed that dissolved organic carbon (DOC), specific UV254 absorbance (SUVA), combined chlorine residual (TCl2), and pH were all significantly related to TOI concentration to varying degrees. A Tobit model was fit to show TOI predictions against observed (measured) TOI values. The model could explain approximately 46% of the variance of TOI concentrations in the treated waters.

An improved method for total organic iodine in drinking water.

A concise, rapid, and sensitive method is developed to measure organically-bound iodine in water. Total organic iodine (TOI) is used as an integrative surrogate that reflects the amount of iodinated organics in a water sample and is quantified using a refined method that builds on previous adsorption and detection approaches. The proposed method combines adsorption, combustion, and trapping of combustion products, with an offline inductively coupled plasma/mass spectrometer (ICP-MS) for iodide detection. During method development, three analytical variables (factors) were varied across two levels each in order to optimize the method for iodine recovery: 1) the sample pH prior to adsorption on the granular activated carbon (GAC); 2) the amount of base addition to the trap solution; and 3) composition of the ICP-MS wash solution. These factors were tested with solutions of eight iodinated model organic compounds, two iodinated inorganic compounds, and field water samples using a full factorial experimental design. An analysis of variance (ANOVA) and related statistical methods were deployed to identify the best combination of conditions (i.e., treatment) that results in the most complete recovery of iodine from the model compounds and the highest rejection of inorganic iodine. The chosen treatment for TOI measurement incorporates a sample pH of less than 1 prior to adsorption onto the GAC, a solution of 2% (v/v) tetramethyl ammonium hydroxide (TMAH) for trapping of combustion products, and a TMAH wash solution of 0.1% (v/v) for the ICP-MS.

Reactor performance in terms of COD and nitrogen removal and bacterial community structure of a three-stage rotating bioelectrochemical contactor.

Integrating microbial fuel cell (MFC) into rotating biological contactor (RBC) creates an opportunity for enhanced removal of COD and nitrogen coupled with energy generation from wastewater. In this study, a three-stage rotating bioelectrochemical contactor (referred to as RBC-MFC unit) integrating MFC with RBC technology was constructed for simultaneous removal of carbonaceous and nitrogenous compounds and electricity generation from a synthetic medium containing acetate and ammonium. The performance of the RBC-MFC unit was compared to a control reactor (referred to as RBC unit) that was operated under the same conditions but without current generation (i.e. open-circuit mode). The effect of hydraulic loading rate (HLR) and COD/N ratio on the performance of the two units was investigated. At low (3.05 gCOD g⁻¹N) and high COD/N ratio (6.64 gCOD g⁻¹N), both units achieved almost similar COD and ammonia-nitrogen removal. However, the RBC-MFC unit achieved significantly higher denitrification and nitrogen removal compared to the RBC unit indicating improved denitrification at the cathode due to current flow. The average voltage under 1000 Ω external resistance ranged between 0.03 and 0.30 V and between 0.02 and 0.21 V for stages 1 and 2 of the RBC-MFC unit. Pyrosequencing analysis of bacterial 16S rRNA gene revealed high bacterial diversity at the anode and cathode of both units. Genera that play a role in nitrification (Nitrospira; Nitrosomonas), denitrification (Comamonas; Thauera) and electricity generation (Geobacter) were identified at the electrodes. Geobacter was only detected on the anode of the RBC-MFC unit. Nitrifiers and denitrifiers were more abundant in the RBC-MFC unit compared to the RBC unit and were largely present on the cathode of both units suggesting that most of the nitrogen removal occurred at the cathode.