Journal of Environmental Engineering

This paper investigated the phosphate removal from aqueous solutions using the ${\mathrm{Fe}}^{2+}\text{-}{\mathrm{KMnO}}_4$ process. Results indicated that the reaction of ${\mathrm{Fe}}^{2+}$ and ${\mathrm{KMnO}}_4$ in the ${\mathrm{Fe}}^{2+}\text{-}{\mathrm{KMnO}}_4$ process could synergistically increase the removal of phosphate compared with those achieved by Fe(III) coagulation and ${\mathrm{MnO}}_2$ adsorption at $\mathrm{pH}\ge 7$. It was necessary that the optimal Fe/P molar ratio was above 3 for effective phosphate removal because of effects of coexisting substances. At pH 7.0, phosphate removal approached a maximum within approximately 5 min. Competing effects of sulfate, bicarbonate, and silicate on phosphate removal were slight. The presence of ${\mathrm{Ca}}^{2+}$ and ${\mathrm{Mg}}^{2+}$ had limited effects on phosphate removal at $\mathrm{pH}\le 4$ but resulted in a significant increase at $\mathrm{pH}\ge 5$. Coprecipitation was considered as the dominant mechanism about phosphate removal in the ${\mathrm{Fe}}^{2+}\text{-}{\mathrm{KMnO}}_4$ process. Fe(III) formed in situ was primarily responsible for phosphate removal. Additionally, in-situ-formed ${\mathrm{MnO}}_2$ also contributed to the phosphate removal through complexation adsorption. The ${\mathrm{Fe}}^{2+}\text{-}{\mathrm{KMnO}}_4$ process had the potential to be utilized in natural water and municipal wastewater treatment for phosphate removal.

This research investigated the mechanism and effect of influencing factors for aqueous ammonia removal by electrolysis in continuous mode with a zeolite-packed electrolysis reactor. Under the conditions of 30-min hydraulic retention time (HRT), 1.8-A current, and $300\text{-}\mathrm{mg}/\mathrm{L}$ chloride ion concentration, the ammonia concentration decreased from 25 to $0.3\mathrm{mg}\mathrm{N}/\mathrm{L}$ within 1.5 h electrolysis time. A total of $4.4\mathrm{mg}\mathrm{N}/\mathrm{L}$ nitrate, $0.03\mathrm{mg}\mathrm{N}/\mathrm{L}$ nitrite, and $0.3–0.8\mathrm{mg}\mathrm{N}/\mathrm{L}$ chloramines were detected in effluent, which accounted for 76% removal of total nitrogen from the aqueous phase. Moreover, the ammonia-presaturated zeolite was almost completely regenerated during the same time period. HRT, current, and chloride ion concentration were found to have a significant effect on ammonia removal as well as zeolite regeneration. Whereas other conditions were fixed, a minimum of 10-min HRT, 1.0-A current, and $210\text{-}\mathrm{mg}/\mathrm{L}$ chloride ion concentration were required to keep the effluent ammonia concentration below $1\mathrm{mg}\mathrm{N}/\mathrm{L}$. For the treatment of municipal wastewater, minimum HRTs of 7.5, 11, and 21 min were suggested for initial ammonia concentrations of 13.5, 30.2, and $53.5\mathrm{mg}\mathrm{N}/\mathrm{L}$ under the conditions of $300\text{-}\mathrm{mg}/\mathrm{L}$ chloride and 1.8-A current.

Biological clogging of filtration and infiltration systems has been acknowledged as a significant problem in the case of wastewater systems. However, scant research has been conducted on biological clogging in storm water filtration and infiltration systems, with the main hypothesis being that biological clogging is insignificant due to the low level of organics present in storm water. This article tested that hypothesis, using a laboratory-based approach. Five replicates of each zeolite-based filter design were dosed with storm water manifesting the following forms: (1) typical storm water (base case); (2) storm water containing very high nutrient concentrations to accelerate biological clogging; (3) typical storm water that was sterilized to suppress biological clogging; and (4) typical storm water with the addition of chlorine to suppress biological activity. The hydraulic performances of these four configurations were monitored over time until the systems were fully clogged. Loss on ignition (LoI) and microscopic analysis of accumulated material within the top layers of the filters were undertaken in an attempt to assess the level of organic matter present in clogging layers of the filters. It was found that all configurations performed differently in comparison to the base case, which represents the most likely set of operational conditions in the field. For instance, the chlorinated filters treated about 30% more storm water compared with the base case. Columns dosed with sterilized storm water treated almost the same volume of storm water but removed a greater quantity of sediment with higher treatment efficiency. Columns dosed with a high level of nutrients clogged more quickly than in the base case. Results of loss on ignition partially confirmed these findings. However, results of microbial cell counts provided tenuous evidence of biological clogging being present. Although the evidence was not overpowering, the variations observed in this study suggest that biological clogging in storm water filters warrants greater attention, which is mostly ignored at present.

With the aim of developing condensed atmospheric water resources as drinking water, atmospheric water samples were collected in six different areas of Shenzhen, China: industrial area, commercial area, road, residential area, green land, and school. The following chemical analytes of atmospheric water were investigated: electrical conductivity (EC), pH, six anions (${\mathrm{F}}^{-}$, ${\mathrm{Cl}}^{-}$, ${\mathrm{NO}}_2^{-}$, ${\mathrm{NO}}_3^{-}$, ${\mathrm{SO}}_4^{2-}$, ${\mathrm{PO}}_4^{3-}$), five cations (${\mathrm{Na}}^{+}$, ${\mathrm{NH}}_4^{+}$, ${\mathrm{K}}^{+}$, ${\mathrm{Mg}}^{2+}$, ${\mathrm{Ca}}^{2+}$), total organic carbon (TOC), total bacterial count, and nine trace metals (Cr, Mn, Ni, Cu, Zn, As, Se, Cd, Pb). Most of analyses met drinking water standards in China, and European Commission, except ${\mathrm{NO}}_2^{-}$ and total bacterial count; after filtered, all indicators for water quality were better than drinking water standards and even tap water. In different areas, atmospheric water quality was affected by certain ambient pollutants and showed its own specialty. In samples from road areas, high concentrations of Mn, ${\mathrm{NH}}_4^{+}$, ${\mathrm{NO}}_2^{-}$, ${\mathrm{SO}}_4^{2-}$, and TOC were attributable to vehicle exhaust and fuel combustion according to correlations between analytes and meteorological data. In industrial areas, high concentrations of ${\mathrm{Cl}}^{-}$ (${2.94\mathrm{mg}\mathrm{L}}^{-1}$), ${\mathrm{SO}}_4^{2-}$ ($5.96\mathrm{mg}{\mathrm{L}}^{-1}$), ${\mathrm{NH}}_4^{+}$ ($6.12\mathrm{mg}{\mathrm{L}}^{-1}$) and ${\mathrm{Ca}}^{2+}$ ($3.80\mathrm{mg}{\mathrm{L}}^{-1}$) were from soil dust and exhaust from two power plants. Acidity potential (AP), neutralization potential (NP) and pAi were discussed in this study.

Deicing salts are spread on roads in northern countries to ensure driver safety during snowfalls. These salts dissolve in road runoff. Various treatment devices have been developed to treat road runoff, but none can remove deicing salt. Phytoabsorption in a constructed wetland is suggested as an innovative option. Two species (Atriplex patula and Typha angustifolia) were selected from previous experiments to be established as the wetland vegetation. However, as this treatment is innovative, some challenges arose during the design process in determining an optimal residence time and substrate nutrient supply to maximize salt removal by plant absorption in a constructed wetland. To overcome those difficulties, this study evaluated the impact of nutrient concentration on plant salt absorption and the removal kinetics of plant salt absorption. Plants were grown in hydroponic conditions in two nutrient solutions with different nutrient concentrations (high and low)—Hoagland $1/4$ and a synthetic road runoff solution—to assess their influence on salt absorption. Plants grown with the Hoagland $1/4$ solution showed the highest aboveground biomass and the highest salt uptake (up to $13\mathrm{g}{\mathrm{Na}}^{+}/{\mathrm{m}}^2$ and $50\mathrm{g}{\mathrm{Cl}}^{-}/{\mathrm{m}}^2$). To determine the salt absorption kinetics, plants were exposed for a period of one week to a solution of $\mathrm{1,500}\mathrm{mg}\mathrm{NaCl}/\mathrm{L}$. Pseudo-first- and pseudo-second order models showed good agreement with experimental data. Salt concentrations in plant tissues increased and reached their maximum after one week. These results determined optimal nutrient supply (Hoagland $1/4$) and residence time (one week) with the aim of improving the performance of salted road runoff treatments by phytoabsorption.

This work studied the use of eucalyptus wood char as a filtration material for fluoride adsorption from drinking water to increase access to safe water. Upon increasing charring temperature, the specific surface area of the eucalyptus wood char increased from 0.9 to $327{\mathrm{m}}^2/\mathrm{g}$; however, the fluoride removal capacity of the unamended eucalyptus wood char was negligible for all charring temperatures. Amendment of the char media with aluminum oxides increased the fluoride removal capacity to $1.6\mathrm{mg}/\mathrm{g}$, demonstrating a significant improvement relative to the unamended wood char. While this adsorptive capacity is not yet as high as values reported for bone char, it is higher than the capacity of some other media currently in use and is a significant improvement over the unamended wood char. Thus, the aluminum oxide modified eucalyptus char may be a helpful alternative for fluoride removal in areas where bone char is not a viable option. This work also studied the possibility of altering the ${\mathrm{pH}}_{\text{PZC}}$, initially 9.6 and 8.2 for wood and bone chars, respectively, to enhance media attraction for fluoride in water. The use of reducing agents actually lowered the ${\mathrm{pH}}_{\text{PZC}}$ to less than 8 for both types of char, but increased the fluoride adsorption capacity of the bone char by approximately 25%, while causing minimal change to the wood char capacity.

Multilinear statistical techniques were used to establish a predictive model for chlorophyll-a concentration in Daechung reservoir, Korea. By relating water quality, weather data, and various hydrological parameters to the chlorophyll-a concentration, a correlation was able to be established between them. $R$ statistical modeling and data mining [model tree, artificial neural network (ANN), and radial basis function (RBF)] with Weka were used specifically employed for the purpose. An empirical model was developed with and without normalization of the input data. The empirical model with normalization of the input data showed excellent correlations ($R^2>0.9$) as compared to that without normalization of the input data ($R^2>0.5$). Based on 10 years of data and selection attributes using Weka preprocess, COD, T-P, and ${\mathrm{PO}}_4\text{-}\mathrm{P}$ were deemed to be the best attributes for the prediction of chlorophyll-a concentration in Daechung reservoir. As compared to classical mechanistic modeling, this approach is significantly less complicated, less time-consuming and more cost effective.

Urbanization and its associated increased impervious footprint lead to stream impairment through erosion, flooding, and augmented pollutant loads. Low-impact development (LID) focuses on disconnecting impervious areas, increasing infiltration and evapotranspiration, and treating storm water on site through the use of storm water control measures (SCMs). In this study, a conventional development (centralized storm-water management) and an adjoining infiltration-based LID commercial site in Raleigh, North Carolina, were compared with respect to hydrology and water quality. The conventional development [2.76 ha, 61% directly connected impervious area (DCIA)] and the LID (2.53 ha, 84% DCIA) had underlying hydrologic soil group B soils. The LID was treated by a mix of green (aboveground) and grey (underground) infrastructure including an underground detention chamber and infiltration gallery, underground and aboveground cisterns, and aboveground swales and bioretention; the conventional development was treated with a dry detention basin and swales. Inflow and outflow runoff volumes and peak flows were normalized by DCIA. For the 47 hydrologic storms monitored, runoff coefficients of 0.02 at the LID site and 0.49 at the conventional site were recorded. The conventional development had an 11-fold higher median peak flow rate than the LID site. For the three storms more intense than the 10-year, 5-min average recurrence interval (ARI) event, the conventional site $Q_p$ was an average of 7.7 times higher than that of the LID. Flow proportional, composite water-quality samples were analyzed for total nitrogen (TN), total phosphorus (TP), total Kjeldahl nitrogen (TKN), total ammoniacal nitrogen (TAN), nitrite-nitrate nitrogen (${\mathrm{NO}}_{\mathrm{X}}$), organic nitrogen (ON), orthophosphate (Ortho-P), and total suspended solids (TSS). Generally, no significant difference in pollutant event mean concentrations (EMCs) was observed between sites. For the 20 water-quality storms sampled, the LID site produced pollutant loadings that were less than 5% of those at the conventional site for all species studied. Results demonstrated highly effective and space-saving solutions when green and grey infrastructure are merged, which is often the case when constructing on high land-cost properties. The exceptional results from this LID were due to (1) an overdesigned system capable of capturing the 77-mm storm, rather than a typical 25-mm storm, and (2) the high infiltration capacity of the type B soils coupled with a high driving head ($\sim 3\mathrm{m}$).

In this paper, the modification of nickel ferrite nanoparticles with cationic surfactant [cetyltrimethyl ammonium bromide (CTAB)] and its capability as a magnetic adsorbent for the removal of direct dyes (Direct Red 31, Direct Red 81, and Direct Red 80) from textile wastewater have been investigated. The Fourier-transformm infrared (FTIR) analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) images, and the determination of isoelectric point (pH at point of zero charge), were used to analyze the morphology to characterize the synthesized magnetic adsorbent. The effect of operating parameters including pH, initial dye concentration, adsorbent dosage, and inorganic salts on the dye removal efficiency was studied. The results showed that varying the pH of solution did not affect the dye removal efficiency. It was also concluded that by increasing the adsorbent dosage the available adsorption sites and the dye removal efficiency would increase. Adsorption isotherms such as Langmuir, Freundlich, and Tempkin were investigated and the results showed that Direct Red 31 and Direct Red 81 had followed all of the mentioned isotherms, and Direct Red 80 had followed Langmuir isotherm. The kinetics studies showed that the dye removal was conformed to the pseudo-second-order kinetic. Finally, it was concluded that the modified nickel ferrite (i.e., CTAB-${\mathrm{NiFe}}_2{\mathrm{O}}_4$) could be used efficiently for dye removal from textile effluents followed by easy magnetic separation of adsorbent.