Environmental Technology

Bui, Huy; Pham, Van Hoi; Pham, Van Dai; Hoang, Thi Hong Cam; Pham, Thanh Binh; Do, Thuy Chi; Ngo, Quang Minh; Nguyen, Thuy Van

doi: 10.1080/09593330.2018.1474268pmid: 29733761

A vast majority of the organic solvents used in industry and laboratories are volatile, hazardous and toxic organic compounds, they are considered as a potent problem for human health and a cause of environmental pollution. Although analytical laboratory methods can determine extremely low solvent concentration, the sensing method with low cost and high sensitivity remains a conundrum. This paper presents and compares three methods (volatile organic compound (VOC), liquid drop and saturated vapour pressure) for determination of organic solvents in a liquid environment by using photonic sensor based on nano-porous silicon (pSi) microcavity structures. Among those, the VOC method provides the highest sensitivity at low solvent volume concentrations because it can create a high vapour pressure of the analyte on the sensor surface owing to the capillary deposition of the organic solvent into the silicon pores. This VOC method consists of three steps: heating the solution with its particular boiling temperature, controlling the flowing gas through liquid and cooling sensor. It delivers the highest sensitivity of 6.9 nm/% at a concentration of 5% and the limit of detection (LOD) of pSi-sensor is 0.014% in case of ethanol in water when using an optical system with a resolution of 0.1 nm. Especially, the VOC method is capable of detecting low volume concentration of methanol in two tested ethanol solutions of 30% (v/v) and 45% (v/v) with the LOD of pSi-sensor up to 0.01% and 0.04%, respectively. This result will help pave a way to control the quality of contaminated liquor beverages.

Pu, Weiwei; Shi, Xuefeng; Wang, Lili; Xu, Jing; Ma, Zhiqiang

doi: 10.1080/09593330.2018.1476593pmid: 29757089

Understanding the potential source regions of air pollutants and their relative contribution from surrounding areas are of great importance for air pollution control strategies in Northern China. Six years of measurement of air pollutants was conducted from 2005 to 2010 in Shangdianzi (SDZ) regional background station. During the study period, the annual average concentrations of sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide and ozone (Ox), and fine particle matter less than or equal to 2.5 μm (PM2.5) range from 15.7 to 20.0 μg/m3, 577.7 to 856.0 μg/m3, 90.4 to 101.8 μg/m3, and 39.8 to 62.4 μg/m3, respectively. In this work, Potential Source Contribution Function (PSCF) and Trajectory Sector Analysis (TSA) methods are applied to identify locations of sources and their relatively contribution of air pollutants at SDZ. PSCF analysis shows that central Inner Mongolia, north Shanxi, west and south Hebei, and west Liaoning are all potential sources of SO2. The North China Plain (NCP) region, especially south Hebei and north Shandong, are major potential source regions for CO, Ox, and PM2.5. Therefore, reducing anthropogenic emissions from the coal industry, biomass burning, agricultural activities, and vehicles in these areas could be an effective way of controlling air pollution at SDZ. Based on the TSA results, the contributions of SO2, CO, Ox, and PM2.5 from long-distance transport are 5.5 μg/m3, 301.4 μg/m3, 14.8 μg/m3, and 25.8 μg/m3, accounting for approximately 22.6%, 32.3%, 13.1%, and 37.5% of the respective air pollutant concentrations at SDZ.

Martínez-Jardines, Miguel; Pérez-Alfaro, Emmanuel; González-Robles, R.O.; Texier, Anne-Claire; Cuervo-López, Flor

doi: 10.1080/09593330.2018.1476594pmid: 29757088

The metabolic and kinetic behaviour of a nitrification process in the presence of 2-chlorophenol (2-CP) was evaluated in two sequencing batch reactors (SBR1, SBR2) inoculated with nitrifying sludge previously exposed to phenolic compounds. The SBR1 was inoculated with sludge previously exposed to 2-CP, while the SBR2 was inoculated with sludge previously exposed to p-cresol. An inhibitory effect of 20 mg 2-CP-C/L on both nitrification processes was observed, as specific rates decreased according to a control assay in the absence of 2-CP. However, the inhibitory effect decreased throughout the cycles. At the end of cycle 6, a stable nitrifying process was observed with the sludge previously exposed to 2-CP (SBR1), as an ammonium consumption efficiency and a nitrate production yield close to 99.6 ± 0.3% and 0.99 ± 0.02 were respectively achieved. Despite a complete ammonium consumption being achieved with the sludge previously exposed to p-cresol (SBR2), partial nitrification was observed as nitrate production yield accounted for 0.28 ± 0.08 and nitrite was accumulated within the culture. Nevertheless, both nitrifying sludges had the ability to completely consume 2-CP. The use of SBR systems with nitrifying sludge previously exposed to 2-CP resulted in a better nitrification performance, thus it may be a good alternative for achieving a stable nitrifying respiratory process where complete and simultaneous ammonium and 2-CP consumption can be acquired.

Wang, Ce; Li, Yongmei; Wang, Yanqiang

doi: 10.1080/09593330.2018.1476595pmid: 29757084

Effects of operating conditions were investigated in terms of water flux, reverse salt flux (RSF) and pollutant rejection in a forward osmosis (FO) membrane system treating synthetic greywater. Changing cross-flow velocity had a slight impact on the performance of the FO membrane. Elevating operating temperature was more effective than increasing draw solution concentration to enhance the water flux. Further observation on the effect of heating mode showed that when the temperature was increased from 20 to 30°C, heating the feed solution (FS) side was better than heating the draw solution (DS) side or heating both sides; further increasing the temperature to 40 and 50°C, heating both the FS and DS achieved much higher water flux compared with only increasing the FS or DS temperature. Under isothermal conditions, a higher water flux and a lower RSF were achieved at 40°C than at other temperatures. Changing either FS or DS temperature had similar influences on water flux and RSF. The FO process revealed high rejection of nitrate (95.7%–100%), ammonia nitrogen (98.8%–100%), total nitrogen (97.4%–99.9%), linear alkylbenzene sulfonate (100%) and Mg (97.5%–100%). A mathematical model that could well simulate the water flux evolution in the present FO system was recommended.

Faustino, L. M.; Braga, A.S.; Sacchi, G.D.; Whitaker, W.; Reali, M.A.P.; Leal Filho, L.S.; Daniel, L.A.

doi: 10.1080/09593330.2018.1477840pmid: 29781404

This paper addresses Dissolved Air Flotation (DAF) process variables, such as the flocculation parameters and the recycle water addition, as well as the pretreatment chemical variables (coagulation conditions), to determine the optimal values for the flotation of iron ore slimes found in a highly turbid water sample from the Gualaxo do Norte River, a tributary of the Doce River Basin in Minas Gerais, Brazil. This work was conducted using a flotatest batch laboratory-scale device to evaluate the effectiveness of DAF for cleaning the water polluted by the Samarco tailings dam leakage and determine the ability of DAF to reduce the water turbidity from 358 NTU to values below 100 NTU, aiming to comply with current legislation. The results showed that the four types of tested coagulants (PAC, ferric chloride, Tanfloc SG and Tanfloc SL) provided adequate conditions for coagulation, flocculation and flotation (in the range of 90–99.6% turbidity reduction). Although the process variables were optimized and low residual turbidity vales were achieved, results revealed that a portion of the flocs settled at the bottom of the flotatest columns, which indicated that the turbidity results represented removal caused by a combination of flotation and sedimentation processes simultaneously.

Wohlmuth da Silva, Salatiel; Arenhart Heberle, Alan Nelson; Pereira Santos, Alexia; Siqueira Rodrigues, Marco Antônio; Pérez-Herranz, Valentín; Moura Bernardes, Andréa

doi: 10.1080/09593330.2018.1478453pmid: 29770731

Antibiotics are not efficiently removed in conventional wastewater treatments. In fact, different advanced oxidation process (AOPs), including ozone, peroxide, UV radiation, among others, are being investigated in the elimination of microcontaminants. Most of AOPs proved to be efficient on the degradation of antibiotics, but the mineralization is on the one hand not evaluated or on the other hand not high. At this work, the UV-based hybrid process, namely Photo-assisted electrochemical oxidation (PEO), was applied, aiming the mineralization of microcontaminants such as the antibiotics Amoxicillin (AMX), Norfloxacin (NOR) and Azithromycin (AZI). The influence of the individual contributions of electrochemical oxidation (EO) and the UV-base processes on the hybrid process (PEO) was analysed. Results showed that AMX and NOR presented higher mineralization rate under direct photolysis than AZI due to the high absorption of UV radiation. For the EO processes, a low mineralization was found for all antibiotics, what was associated to a mass-transport limitation related to the low concentration of contaminants (200 µg/L). Besides that, an increase in mineralization was found, when heterogeneous photocatalysis and EO are compared, due to the influence of UV radiation, which overcomes the mass-transport limitations. Although the UV-based processes control the reaction pathway that leads to mineralization, the best results to mineralize the antibiotics were achieved by PEO hybrid process. This can be explained by the synergistic effect of the processes that constitute them. A higher mineralization was achieved, which is an important and useful finding to avoid the discharge of microcontaminants in the environment.

Vardanyan, Narine; Sevoyan, Garegin; Navasardyan, Taron; Vardanyan, Arevik

doi: 10.1080/09593330.2018.1478454pmid: 29781399

Possibilities for the recovery of non-ferrous and precious metals from Kapan polymetallic mine tailings (Armenia) were studied. The aim of this paper was to study the possibilities of bioleaching of samples of concentrated tailings by the natural microbial consortium of drainage water. The extent of extraction of metals from the samples of concentrated tailings by natural microbial consortium reached 41–55% and 53–73% for copper and zinc, respectively. Metal leaching efficiencies of pure culture Leptospirillum ferrooxidans Teg were higher, namely 47–93% and 73–81% for copper and zinc, respectively. The content of gold in solid phase of tailings increased about 7–16% and 2–9% after bio-oxidation process by L. ferrooxidans Teg and natural microbial consortium, respectively. It was shown that bioleaching of the samples of tailings could be performed using the natural consortium of drainage water. However, to increase the intensity of the recovery of valuable metals, natural consortium of drainage water combined with iron-oxidizing L. ferrooxidans Teg has been proposed.

Katahira, Kenshi; Moriwaki, Hiroshi; Kamura, Kazuo; Yamazaki, Hideo

doi: 10.1080/09593330.2018.1478885pmid: 29781400

This study developed the 2-step extraction method which eluted the Pb adsorbing on the surface of sediments in the first solution by aqua regia and extracted the Pb absorbed inside particles into the second solution by mixed acid of nitric acid, hydrofluoric acid and hydrogen peroxide solution. We applied the method to sediments in the enclosed water area and found out that the isotope ratios of Pb in the second solution represented those of natural origin. This advantage of the method makes it possible to distinguish the Pb between natural origin and anthropogenic source on the basis of the isotope ratios. The results showed that the method was useful to discuss the Pb sources and that anthropogenic Pb in the sediment samples analysed was mainly derived from China because of transboundary air pollution.

Park, Seong-Jik; Kang, Ku; Lee, Chang-Gu; Choi, Jae-Woo

doi: 10.1080/09593330.2018.1478886pmid: 29774827

The objectives of this study are to assess the effectiveness of limestone (LS), steel slag (SS), and activated carbon (AC) as capping materials to sequester trace metals including As, Cd, Cr, Cu, Ni, Pb, and Zn in heavily contaminated marine sediments and to minimize the release of these metals into the water column. A flat flow tank was filled with 10 mm of capping material, contaminated sediments, and seawater, and the metal concentrations were monitored over 32 d. After completion of the flow tank experiments, the sediments below the capping material were sampled and were sequentially extracted. SS effectively reduced the As, Cr, Cu, Ni, Pb, and particularly Cd elution from the contaminated sediments to the overlying seawater. Adsorption and surface precipitation were the key mechanisms for interrupting the release of cationic trace metals by SS. LS was appropriate for interrupting the release of only Cu and Pb with high hydrolysis reaction constants. AC capping could interrupt the release of Cr, Cu, Ni, and particularly Zn from the sediments by binding with the metals via electrostatic interaction. The results obtained from the sequential extraction revealed that LS capping is appropriate for stabilizing Zn, whereas AC is appropriate for Cd and Pb. LS, SS, and AC can be applied effectively for remediation of sediments contaminated by trace metals because it interrupts their release and stabilizes the trace metals in the sediments.

Medeiros, Raphael Corrêa; Daniel, Luiz Antonio; de Oliveira, Gabriela Laila; Hoffmann, Maria Teresa

doi: 10.1080/09593330.2018.1480063pmid: 29813004

The protozoa Giardia and Cryptosporidium are associated with numerous outbreaks of waterborne diseases worldwide. This study aimed to evaluate the concentration of Giardia spp. cysts, Cryptosporidium spp. oocysts, total coliforms, Escherichia coli and Clostridium perfringens in raw wastewater and their removals at UASB reactor, activated sludge system (operated conventionally and extended aeration) and slow sand filtration. Giardia spp. cysts were present in 100% and Cryptosporidium spp. oocysts in 31.4% of the analysed wastewater samples. The UASB reactor followed by activated sludge system obtained approximately 2.0 log of removal for total coliforms and E. coli, whereas for C. perfringens and Giardia spp. cysts, it obtained 1 log. There was a high percentage of (oo)cysts still viable after secondary treatment, therefore, the risk of contamination of water courses and, consequently, for public health is considerable. However, after tertiary filtration, no (oo)cysts were found in any of the filtered effluent samples, being a good option for future reuse. Seasonal variations did not affect the concentrations and removals of microorganisms observed. Lack of correlations of concentrations of indicator microorganisms and (oo)cysts raise caveats and doubts regarding the true microbiological quality when using only indicator microorganisms.