Journal of Environmental Engineering

The impacts of bromide concentration and natural organic matter (NOM) characteristics on the formation and speciation of disinfection by-products (DBPs) in chlorinated NOM fractions were investigated. A total of 20 bulk water NOM fractions with a wide range of specific ultraviolet (UV) absorbance $\left({\mathrm{SUVA}}_{254}\right)$ values were obtained from a source water employing XAD-8 or XAD-4 resin adsorption in completely mixed batch reactors. SUVA was not a good predictor of DBP [trihalomethanes (THMs), haloacetic acids (HAAs), and adsorbable organic halogens (AOX)] formation and speciation. The destruction in the ${\mathrm{UV}}_{254}$ absorbance from chlorination did not correlate with DBP formation at any bromide level. NOM moieties which do not absorb UV light at $254\mathrm{nm}$ significantly contributed to DBP formation. Mass balance calculations on halogens using THMs, HAAs, and AOX data indicated that significant amounts of DBPs ( $>54\%$ of AOX) other than THMs and HAAs were formed in NOM fractions with $60–110\mathrm{\mu }\mathrm{g}∕\mathrm{L}$ bromide concentration. The relative occurrence of such other halogenated by-products decreased with increasing bromide concentrations up to $500\mathrm{\mu }\mathrm{g}∕\mathrm{L}$ level. NOM in the studied water was more susceptible to the formation of brominated THM species as opposed to brominated HAAs. At constant dissolved organic carbon concentration, chlorine dose and pH, increasing bromide concentrations in NOM fractions increased the total concentrations of DBPs and resulted in a shift toward the formation of brominated species. Further, increasing bromide concentrations increased the spectrum of detected species (i.e., occurrence of all nine HAAs) and provided a competitive advantage to THM and HAA precursors in NOM over precursors of other DBPs.

Reclamation of biologically treated wastewaters is frequently enhanced with the use of constructed wetlands and wastewater lagoons that remove nutrients and persistent organic pollutants. To better design systems utilizing uptake of persistent organic contaminants by aquatic plants, a quantitative description of partitioning of contaminants into aquatic plants is required. The uptake of halogenated phenols by Lemna minor was investigated to examine uptake of a family of closely related organic contaminants by a common aquatic plant. Batch experiments with L. minor $\left(52\mathrm{h}\right)$ and 14 halogenated phenols were operated at nontoxic concentration levels with $>90\%$ of aqueous-phase contaminant in the protonated form. Pseudo-first-order rate coefficients determined using nonlinear regression of time series concentration data described contaminant uptake. Changing halogen substituent or number of halogen substituents did not affect uptake rate, however halogen positioning did affect contaminant uptake rate. Uptake rate constants were not correlated with $\log K_{\mathrm{ow}}$ , however, uptake rate was correlated with parameters related to rate of internal plant enzymatic transformation. Therefore, contaminant uptake rate appeared to proceed at a rate dependent on internal enzymatic transformation.

A laboratory-scale sequencing batch reactor was operated and the dynamics of Rhodocyclus-related phosphorus-accumulating organisms (PAOs) population was monitored. After the system reached a steady state and showed a stable enhanced biological phosphorus removal status, the organic loading rate was increased from 160 to $\mathrm{1,020}\mathrm{g}\mathrm{COD}{\mathrm{m}}^{-3}{\mathrm{cycle}}^{-1}$ in five steps. When the P storage capacity reached maximum at $330\mathrm{g}\mathrm{COD}{\mathrm{m}}^{-3}{\mathrm{cycle}}^{-1}$ , the system lost the stability and the effluent phosphorus concentration fluctuated. As the organic loading rate increased from 160 to $\mathrm{1,020}\mathrm{g}\mathrm{COD}{\mathrm{m}}^{-3}{\mathrm{cycle}}^{-1}$ , the PAO population decreased from $83.8\pm 4.9$ to $32.2\pm 16.2$ % and internal polyphosphate content decreased from 0.20 to $0.03\mathrm{mg}\mathrm{P}\mathrm{mg}{\mathrm{VSS}}^{-1}$ . Phosphate-accumulating metabolism was weakened as the organic loading rate increased and PAO population decreased concomitantly, whereas glycogen-accumulating metabolism increased at high organic loading rates as supported by the increased intracellular glycogen content and production of a higher fraction of intracellular poly- $\beta$ -hydroxyl valerate.

A model aimed at calculating the aeration efficiency of a passively aerated biological vertical bed unit is presented. The model allows the calculation of the mass of air that would flow via convection into the vertical bed, therefore enabling the prediction of the maximal capacity of the bed as an aerobic biological reactor. Aeration efficiency, defined as the volume of air that would enter the bottom of the bed as a function of the volume of water that is drained from it, is predicted in the model as a function of the mean particle size of the gravel media, and the diameter and number of the aeration tubes installed. The model was calibrated in the laboratory and verified using results from a pilot scale vertical bed treating secondary municipal wastewater effluents. The principal model equation is: $E_{\mathrm{PAVB}}=N_P{D}_p^4∕(N_P{D}_p^4+0.285p{D}_r^2{\overline{\delta }}^2)$ , where $E_{\mathrm{PAFB}}$ =efficiency of the passive air pump (—); $N_P$ =number of aeration pipes (—); $D_p$ =aeration pipes’ diameter (m); $p$ =medium porosity (—); and $D_r$ =vertical bed diameter (m).

2,2,3,3-Tetra-fluoro-propanol (TFP) has been extensively used in compact disk-recordable and digital versatile disk-recordable manufacture and a large amount of wastewater containing the chemical is being discharged. This investigation evaluates the feasibility and effectiveness of the use of UV, ${\mathrm{O}}_3$ , and $\mathrm{UV}∕{\mathrm{O}}_3$ to degrade aqueous TFP. TFP oxidation tests were performed with initial TFP concentrations of $772–887\mathrm{mg}∕\mathrm{L}$ with various solution pH values (acidic, alkaline, uncontrolled), solution temperatures (26, 37, 48, and $60°\mathrm{C}$ ), and UV wavelengths (254 and $185\mathrm{nm}$ ). Experimental results demonstrated that alkaline conditions favor the TFP degradation and increase the mass of TFP decomposition per unit mass of ozone consumption, in both ${\mathrm{UV}}_{254\mathrm{nm}}∕{\mathrm{O}}_3$ and ${\mathrm{UV}}_{185\mathrm{nm}}∕{\mathrm{O}}_3$ processes. There was no significant difference in the rate of TFP degradation when using either ${\mathrm{UV}}_{254\mathrm{nm}}$ or ${\mathrm{UV}}_{185\mathrm{nm}}$ . TFP exhibited zero-order degradation kinetics when sufficient ozone was supplied. A higher oxidation temperature was found to be no help for the $\mathrm{UV}∕{\mathrm{O}}_3$ oxidation of TFP in the tested concentration and temperature ranges. The cost of the ${\mathrm{UV}}_{254\mathrm{nm}}∕{\mathrm{O}}_3$ or ${\mathrm{UV}}_{185\mathrm{nm}}∕{\mathrm{O}}_3$ per unit volume of wastewater with an initial TFP concentration of $\mathrm{3,387}\mathrm{mg}∕\mathrm{L}$ is comparable to that of the Fered–Fenton process as described in the literature.

Field experiments were conducted at a Class B biosolids land application site in central Arizona to measure, model, and source-track the off-site transport of aerosols emitted when biosolids were disk-incorporated into soils. Real-time ${\mathrm{PM}}_{10}$ monitoring provided time-resolved aerosol information sufficient for verifying both off-site concentration and off-site exposure time model results. Under the conditions considered and at a distance of $165\mathrm{m}$ from the aerosol source, biosolids disk-incorporation resulted in an intermittent exposure to biosolids-derived aerosol concentration between 15 and $40\mathrm{\mu }\mathrm{g}∕{\mathrm{m}}^3$ and an inhalable biosolids dose between 2 and $8\mathrm{\mu }\mathrm{g}$ . Transport modeling predicted that these doses will decrease with increasing wind speed. In addition, three DNA sequence-based biosolids source tracking methods were applied to aerosol samples and confirmed the presence of biosolids in aerosols at 5, 65, and $165\mathrm{m}$ from the aerosol source. Field measurements and modeling indicate that the nature of biosolids-derived aerosol exposure is a series of intermittent high concentration puffs, rather than a continuous low concentration.

A model for predicting air permeability $\left(k_a\right)$ as function of air-filled porosity $\left(\epsilon \right)$ in undisturbed subsurface sandy soils, relevant for vapor extraction system design and operation, was developed using data from eight undisturbed soils (approximately 240 samples). The model requires only one measurement of corresponding values of $k_a$ and $\epsilon$ as input to estimate $k_a$ at any desired value of $\epsilon$ . The soils used represent both urban, agricultural and forest locations. The model is based on the fact that the relationships between $\log \left(k_a\right)$ and $\log \left(\epsilon \right)$ in sandy soils are approximately linear and on average pass through a common interception point, although with very different slopes. An expression for predicting $k_a$ at $-100\mathrm{cm}{\mathrm{H}}_2\mathrm{O}$ soil water potential $\left(k_{a100}\right)$ from $\epsilon$ at the same potential $\left({\epsilon }_{100}\right)$ for sandy soils was also developed. Using this expression together with the new $k_a\left(\epsilon \right)$ predictive model enables prediction of the entire $k_a\left(\epsilon \right)$ relation without any $k_a$ measurements using only a measurement of ${\epsilon }_{100}$ . This approach results in only a slightly higher prediction uncertainty. The model was tested against an independent set of data from five undisturbed sandy soils (22 samples) and close agreement between measured and predicted air permeability values was found.