Journal of Environmental Engineering

Small wastewater systems serving less than 10,000 population equivalents (p.e.) face a wide range of challenges due to technical and managerial capacity issues, limited resources, and the need to reduce environmental impacts. Based on the wide range of challenges of small systems, the authors of this manuscript developed the social, environmental, and economic wastewater decision support tool (SEE WWDST) to aid decision makers in comparing the sustainability of treatment alternatives. The tool uses multi-criteria decision analysis to produce a single SEE impact score that assesses 12 sustainability metrics across three larger categories: economic performance (e.g., net present worth of costs, affordability), environmental performance (e.g., carbon footprint, eutrophication, water reclaimed), and social performance (e.g., maintenance time, employee training, degree of automation, operator certification requirement, system intrusiveness, daily, and seasonal resilience). This paper compares the performance of three onsite wastewater treatment systems in Florida. The three systems evaluated include: (1) a passive septic tank effluent biofilter (STEB) system, (2) a mechanized aerobic treatment unit (ATU) system, and (3) a passive clay, sulfur, and shell biofilter (CSSB) system. The passive CSSB system was found to be the preferred system due to its lower present worth of cost, lower carbon footprint and eutrophication potential, and better performance for various social factors (e.g., maintenance time, degree of automation, system intrusiveness). The passive STEB system was the second preferred alternative, despite having a worse social performance and the highest present worth of cost. The systems were then assessed using even, social, environmental, and economic weighting preferences and a sensitivity analysis was conducted. In spite of shifts in weighting preference and changes to input data parameters to assess sensitivity, the passive CSSB system was found to be the preferred alternative. This paper highlights the importance of using triple bottom line sustainability metrics to assess small wastewater treatment alternatives using a novel decision support tool.

This study examined the potential of the aquatic macrophyte Eichhornia crassipes for bioaccumulating hexavalent chromium and its effects on the plant’s morphology. The macrophytes were exposed to different concentrations of Cr (VI) ($0–100\mathrm{mg}{\mathrm{L}}^{-1}$) in 20% full-strength Hoagland nutrient solution for 10 days. Changes in the Cr (VI) concentrations were measured in the media and in specific plant tissues, i.e., roots, shoots, and leaves. The bioconcentration factor (BCF) in all plant parts and the translocation factor (TF) within plant tissues were calculated twice during the experiment. Results demonstrated that E. crassipes accumulated high concentrations of Cr (VI) in all plant tissues examined in a dose-specific manner. High BCF was observed in the plant roots for concentrations up to $60\mathrm{mg}{\mathrm{L}}^{-1}$, after which the accumulation in shoots and leaves was greater than in roots. The results from E. crassipes survivorship indicated that $40\mathrm{mg}{\mathrm{L}}^{-1}$ is the threshold concentration for their survival under Cr (VI) stress. Morphological changes in the plants were examined by monitoring the change in the number of leaves and plant height under varying Cr (VI) concentrations. Impeded growth was observed due to increasing Cr (VI) concentration with maximum growth in the control group with no Cr (VI). Evapotranspiration losses were monitored and found to be minimal in experimental groups with high concentrations, displaying a negative correlation with Cr (VI) contamination. Physicochemical parameters including pH, electrical conductivity, oxidation-reduction potential, and color were also found to be significantly correlated with Cr (VI) concentration and time. The results demonstrated significant Cr (VI) accumulation in E. crassipes as well as noticeable morphological changes, making E. crassipes a suitable organism for biomonitoring and remediating Cr-contaminated sites over a relatively short time period.

Antibiotic resistance has become a major global challenge in recent years. Abusing and misusing antibiotics leads to the widespread spread of resistance genes in the water environment, which poses great challenges to drinking water safety and human health. Traditional disinfection methods are not effective against antibiotic resistance genes. While ultraviolet (UV) disinfection is widely used for its efficient bactericidal effect, its effect on tetracycline resistance genes is poor, and there is no disinfection persistence, as antibiotic resistance bacteria are easily restored by photoreactivation. As a green way of disinfection with continuous disinfection and without disinfection by-products, tea polyphenols have gradually attracted wide attention from researchers, because they can serve as an assistant disinfectant for ultraviolet disinfection. Studies have shown that tea polyphenols as an assistant disinfectant can effectively compensate for the disadvantages of ultraviolet disinfection. In this study, the effects of a UV-tea polyphenols combined disinfection process on resistance genes were analyzed by metagenomics sequencing, and the combined process showed better removal of tetracycline and $\beta$-lactam resistance genes. It is suitable for raw water containing higher concentrations of specific resistance genes. This combined disinfection process controls the spread of resistance genes mainly through the direct disruption of resistance genes and the effective inhibition and killing of resistant bacteria. This is important for the optimization of resistance genes removal capability in water treatment.

Abstract

The combination of activated sludge and microalgae in a membrane bioreactor (MBR) is a new promising solution in municipal wastewater treatment to remove nitrate (${\mathrm{NO}}_3^{-}$) and phosphate (${\mathrm{PO}}_4^{3-}$). Furthermore, municipal wastewater contains a considerable amount of ${\mathrm{NO}}_3^{-}$ and ${\mathrm{PO}}_4^{3-}$, which is suitable for microalgae growth. It can be concluded from the literature that there is a direct relationship between microalgae biomass production and nutrient removal. Thus, the light cycle and the initial microalgae concentration (as two main factors for microalgae growth) can be optimized. In this study, the biomass productivity in three light-dark (L-D) cycles (h) (24-0, 16-8, and 12-12 h) and initial concentrations (0.5, 1, and $1.5\mathrm{g}·{\mathrm{L}}^{-1}$) were measured. The L-D cycle of 24-0 and the initial concentration of $1\mathrm{g}·{\mathrm{L}}^{-1}$ was used as the chosen parameter in the membrane photobioreactor (MPBR) containing microalgae. The initial concentration of nitrate, phosphate, chemical oxygen demand (COD), and total dissolved solids (TDS) was investigated. The investigation was performed first on the MBR containing activated sludge and then on the treated wastewater via MBR to MPBR containing microalgae (MBR-MPBR). The duration of the experiment was 133 days. During this period, the removal amount of COD, nitrate, and phosphate was reported at 92.35%, 47.55%, and 36.46% in the MBR, respectively. In MBR-MPBR, the average of nitrate and phosphate removal increased to 93.88% and 88.44%, respectively. However, TDS did not show any notable alterations in both operating systems. According to the findings, the second stage of the treatment process, MBR-MPBR outperformed the MBR system in terms of ${\mathrm{NO}}_3^{-}$ and ${\mathrm{PO}}_4^{3-}$ removal.

Practical Applications

A membrane bioreactor is a combination of the membrane with microorganisms used in the wastewater treatment process. Due to their simple structure, small size, and high efficiency in removing organic and inorganic substances, membrane bioreactors have been considered for industrial and urban wastewater treatment. Operational parameters in the design of these systems have a significant impact on nutrient removal efficiency. Furthermore, based on the high efficiency of microalgae in removing nutrients, its combination with activated sludge increases the efficiency of the bioreactor. In this work, some operating parameters such as the light-dark cycle and initial concentration of microalgae were optimized in the membrane bioreactor. Then, two various systems, namely a membrane bioreactor (containing activated sludge) and a two-stage membrane bioreactor (containing activated sludge and microalgae), were compared. In this regard, the total dissolved solids, chemical oxygen demand, nitrate, and phosphate removal were investigated. All these values were recorded under optimal conditions of the light-dark cycle and initial concentration of microalgae in two different systems.

Abstract

The waterborne outbreak potential of Cryptosporidium and Giardia is recognized by public water supply agencies, motivating monitoring of surface sources to meet applicable drinking water regulations. In this study, data from 10 or more years of continuous monitoring at several sites were compiled and analyzed to describe patterns of occurrence and to outline data analysis procedures to better inform watershed management and treatment system management for control of these pathogens. Data were analyzed to identify parameters that enable risk characterization, the median and standard deviation for annual data sets. These values, monitored for a sequence of years, indicate trends related to watershed processes and provide guidance for watershed management. The scope of annual variations, in combination with tracking concentrations corresponding to short-term (seasonal) water quality variations, provides essential information for treatment system management. The patterns of Cryptosporidium and Giardia occurrence over 10 or more years demonstrates their continuous presence in virtually all surface water sources. The results provide a direct means of quantifying risk relative to other years at a single site or to occurrence similarly described elsewhere. Reflection on the results shows that inference of absence from negative findings is no longer acceptable. Clear understanding of the data presented here provide a basis for monitoring that is both more effective and more efficient, providing real value for the substantial investment that monitoring requires.

Practical Applications

Long-term, $10+\text{-}\mathrm{year}$ data for concentrations of Cryptosporidium and Giardia describe their continuous presence and variations over time. Given the high cost of monitoring, a clear understanding of monitoring objective is essential. A continuing record provides a basis for comparing concentration-based risks over time and comparisons with concentrations monitored at other locations. This provides a foundation for watershed management and for treatment system management in relation to risk. The description of monitoring and data analysis principles provides guidance for the development of value-oriented monitoring of these waterborne pathogens and, ultimately, an efficient and effective monitoring program that will satisfy health-based and regulatory monitoring needs.

In recent years, mining pollution has become a serious worldwide public health concern. One major issue in this field is concerned with arsenic-contaminated sediment. This paper, therefore, intends to determine the extent to which enhanced electrokinetic (EK) remediation is effective for remedying a case study of arsenic-contaminated sediment. The first section of this paper is devoted to determining the best enhancement agent at various solution concentrations and better discovering soil–metal action and reaction by leaching experiments. The sediment was collected from the zinc processing plant cold filter cake (CFC) in Shams Abad Industrial City, Iran, with a $\mathrm{5,700}\mathrm{mg}/\mathrm{kg}$ concentration of arsenic. In the second section of the study, ethylenediaminetetraacetic acid, citric acid, and sodium hydroxide as electrolyte conditioning solutions and sodium hydroxide for pretreatment have been evaluated as enhancement techniques for the remediation of arsenic-contaminated sediment during the electrokinetic method in tests with a duration of 8 days. Also, increasing the voltage gradient from 1 to $1.5\mathrm{V}/\mathrm{cm}$ was assessed as another enhancement technique for improving the electrokinetic removal efficiency of arsenic. Finally, the result of experiments showed no significant increase in arsenic removal efficiency in using pretreatment and increasing the applied voltage; however, interestingly, using citric acid 0.5 M as the catholyte solution enhanced the removal efficiency up to 33.51%.

The chloramination of bromide containing waters results in the formation of bromine containing haloamines: monobromamine (${\mathrm{NH}}_2\mathrm{Br}$), dibromamine (${\mathrm{NHBr}}_2$), and bromochloramine (NHBrCl). Many studies have directly shown that bromamines are more reactive than chloramines in oxidation and substitution reactions with organic water constituents because the bromine atom in oxidants is more labile than the chlorine atom. However, similar studies have not been performed with NHBrCl. It has been assumed that NHBrCl has similar reactivity as bromamines with organic constituents in both oxidation and substitution reactions because NHBrCl, like bromamines, rapidly oxidizes N,N-diethyl-p-phenylenediamine. In this study, we examined the reactivity of NHBrCl with phenol red to determine if NHBrCl reacts as readily as bromamines in an isolated substitution reaction. NHBrCl was synthesized two ways to assess whether NHBrCl or the highly reactive intermediates, bromine chloride (BrCl) and molecular bromine (${\mathrm{Br}}_2$), were responsible for bromine substitution of phenol red. NHBrCl was found to be much less reactive than bromamines with phenol red and that BrCl and ${\mathrm{Br}}_2$ appeared to be the true brominating agents in solutions where NHBrCl is formed. This work highlights the need to reexamine what the true brominating agents are in chloraminated waters containing bromide.