Environmental Health Engineering and Management Journal
Volume:7 Issue: 1, Winter 2020

The utilization of microalgae as a renewable energy is an important aspect in solving shortage of future oil reserve in 15 years. One of the renewable energy sources is microalgae biodiesel. Palm oil mill effluent (POME) is a wastewater that has a high content of organic materials. These organic materials can be used as growth nutrients for microalgae. Chlorella pyrenoidosa is one of the most potential microalgae used as a raw material for the production of biodiesel since it contains lipids (8%-35%).

Chlorella pyrenoidosa was cultured on the POME medium with concentrations of 0%, 25%, 50%, 75%, and 100%v with addition of synthetic nutrients (urea: TSP) at the ratios of 2:1 ; 1:2 ; 0.5:1 in a 500 mL Erlenmeyer flask, at pH 6-8, aeration using aquarium pumps, and using LED lights (3000 lux).

It was revealed that at POME concentration of 25% and with addition of urea: TSP at a ratio of 2:1, the optimum specific growth rate (0.306/day) with the highest number of cells was 3.530 × 107 cells/mL and the highest lipid content was 36% of its dry weight. The removal efficiency of POME could be obtained from the removal efficiency of chemical oxygen demand (COD), total nitrogen, and orthophosphate (P-PO4), which was 70, 90.42, and 81.12%, respectively.

According to the results, under appropriate culture conditions, C. pyrenoidosa can produce lipids with good use of nutrients contained in the POME medium.

Nowadays, uncontrolled use of chemical fertilizers in agriculture is one of the reasons for the entry of heavy metals into the environment. In this study, the heavy metals contamination of the soils enriched with compost and chemical fertilizers in the North of Iran and its ecological risk assessment
were evaluated.

In this study, 108 soil samples were collected from agricultural soils of some places of Babol in Mazandaran province. An atomic absorption spectrophotometer (PG-990) was used to determine the concentrations of lead, cadmium, and zinc in the soil samples. The assessment of soil contamination was performed by the contamination factor, degree of contamination indices, and the potential ecological risk of the heavy metals. Data were analyzed using SPSS version 22. Descriptive and chi-square tests were used to compare the mean with existing standards. Significant level was considered at P < 0.05.

The highest lead concentration (35.7 ± 9.5 mg/kg) was observed at 5-cm depth, and the maximum cadmium (1.1 ± 0.2 mg/kg) and zinc (88 ± 22.6 mg/kg) concentrations were observed at 15-cm depth. The results showed that lead, cadmium, and zinc concentrations in the agricultural soils enriched with compost fertilizers were acceptable, but agricultural soils enriched with chemical fertilizers indicated higher content than those enriched with compost fertilizers and higher than the maximum allowable concentration. The maximum contamination degree, pollution index, and potential ecological risk in the agricultural soils enriched with the chemical fertilizers were 15.77, 1.97, and 293.48, respectively, and these soils had low potential pollution and moderate ecological risks.

According to the results, it is necessary to use compost fertilizers for the agricultural soils enrichment.

Soil remediation is one the important problem in environmental studies. Thus, this research was conducted to evaluate the effect of organic chelates and gibberellic acid (GA3) on the degradation of crude oil in the soil co-contaminated with Ni and crude oil under canola cultivation.

For treatments, HEDTA and NTA chelates at rates of 0 and 2.5 mmol/kg soil and foliar GA3 (0 (GA3(-) and 0.05 (GA3(+) mM) were used. In addition, the soil was polluted with Ni (0 and 100 mg Ni/kg soil) and crude oil at rates of 0, 2, and 4% (W/W). The plant used in this experiment was canola. The concentration of Ni in soil and plant was measured using atomic absorption spectroscopy (AAS). The concentration of total petroleum hydrocarbon (TPH) was measured using GC-mass. The mean differences were calculated according to the least significant difference (LSD) test.

The greatest degradation of crude oil belonged to the non-Ni-polluted soil under cultivation of GA3-treated plant, while the lowest one was observed in the soil received the greatest level of HEDTA and NTA chelates. Applying 0.05 mM GA3 foliar significantly increased the degradation of crude oil in soil and Ni in plant shoot by 12.1 and 8.3%, respectively. In addition, soil microbial respiration was also increased by 11.3%.

HEDTA, NTA, and GA3 had a significant effect on the Ni phytoremediation efficiency and degradation of crude oil in soil that is a positive point in environmental pollution. However, the role of soil physico-chemical properties on the phytoremediation efficiency cannot be ignored.

Phenanthrene (PHE) is a polycyclic aromatic hydrocarbon (PAH) with crystalline structure of C14H10, which was produced from incomplete combustion of hydrocarbons and fossil fuels and can cause harmful biological effects. Bioremediation using halophilic bacteria is payed attention over chemical methods due to considerable benefits.

In the present study, a halo-tolerant bacterium Bacillus kochii strain AHV-KH14 was isolated from municipal compost, and used for the bioremediation of PHE from the contaminated soil. The effects of operational parameters including soil/water ratio, initial inoculum size, PHE concentration, and salinity on the bioremediation performance were investigated.

A biodegradation efficiency of about to 98% was obtained for PHE concentration of 50 mg/kg and salinity level of 1.5%. By increasing salinity content PHE concentration, PHE biodegradation rate decreased significantly. It was found that the bioremediation efficiency decreased with increasing PHE concentration. It was also revealed that for the unwashed soil sample, cumulative concentrations of different hydrocarbons played an important role in decreasing the efficiency of bioremediation.

A natural hydrocarbon-contaminated soil sample with total petroleum hydrocarbon (TPH) concentration of 2350 mg/kg was subjected to bioremediation using the selected conditions of operational parameters, and a biodegradation rate of 17.7% was obtained.

This study aimed to model optimization of strategic environmental management decisions in the operation of reverse osmosis desalination, emphasizing the costs required for the environmental protection during the production of freshwater using reverse osmosis technology.

This analytical research was conducted in five cities of Hormozgan province in Iran for 18 months from February 2018 to September 2019. The research includes eight phases of defining the research problem, data collection, preliminary data analysis and decision criteria, mathematical modeling, model validation, information preparation, analysis and finally discussion, conclusions and suggestions. The main environmental issues were the carbon dioxide (CO2) release rate due to power demand and rejected brine water (RBW) were entered the mathematical model.

The desalination plants of Abu Musa, Bandar Abbas, Qeshm, Sirik, and Hormoz with water production flow rate of 2100, 89 000, 5300, 3300 and 1500 m3/d can generate 2360.82, 100053.80, 5958.260, 3709.86 and 1686.30 tons/year of CO2 emissions respectively. This output requires 1.35, 57.47,3.42, 2.13 and 0.97 million USD for controlling the process, respectively. For reduction of the negative effect of RBW 0.75, 22.79, 1.78, 1.15 and 0.55 million USD respectively, is needed.

Recommendations for environmental impacts protection of RBW, for desalination capacity up to 50 000 m3/d, are; (a) for desalination capacity up to 50 000 m3/d; dilution the RBW using raw water before entering into the sea, (b) for capacity of 50 000-100 000 m3/d; dispersing RBW in sea using diffuser, and (c) for capacity more than 100 000 m3/d; hybrid water desalination plants and power plant. Application of power plant cooling water to dilute RBW may reduce cost.

Today, advances in different areas of science and technology along with their application in industries have led to an increase in dangerous pollutants which can resist biodegradation. Volatile organic compounds (VOCs) are regarded as important factors of air pollution in closed environments. Xylene is one of these compounds which is produced in mass quantities and widely used in industries, therefore, the removal of this compound is necessary. One of the available technologies for removing this compound is photocatalytic degradation. The present study aimed to determine the efficiency of photocatalytic removal of xylene as a pollutant in air using TiO2-ZnO nanoparticles and TiO2-ZnO composite coated on activated carbon under ultraviolet radiation.

In this experimental study, after coating of the nanoparticles on activated carbon, the produced catalysts with a specific surface area were characterized using Brunauer-Emmett-Teller (BET) surface area and porosity analysis, scanning electron microscope (SEM), and the type and percentage of the main elements present in the bed were determined using energy dispersive x-ray spectroscopy (EDS). The tests were carried out at laboratory scale and ambient temperature. In order to produce polluted air containing 100 ppm xylene vapor at a specific flow rate and concentration, a dynamic concentrator system was used. The removal of xylene was investigated under continuous flow mode.

The results of the specific surface area using BET analysis and SEM images showed that nanoparticles were well coated on activated carbon. According to the results of the photocatalytic removal, the efficiencies of photocatalytic removal of xylene by AC/ZnO 5%, AC/TiO2 15%, and AC/3TiO2/1ZnO were 80.1, 89, and 95.1%, respectively.

According to the results, the use of ZnO-TiO2 nanocomposite on activated carbon can be an appropriate method for the photocatalytic removal of xylene from polluted air.

Arsenic (AS) is a heavy metal pollutant in water that has been known as one of the most important environmental contaminants due to its serious effects on both human health and the environment. This study was conducted to investigate the efficiency of calcined Co/Fe/Al LDH@Fe3O4@PA as a new magnetic bio-sorbent for AS removal from the polluted water.

At first, magnetic ternary calcined layered double hydroxide (Co/Fe/Al LDH) was synthesized through co-precipitation procedure. The synthesized CLDH was modified with phenylalanine amino acid, named CLDH@Fe3O4@PA. Infrared spectroscopy, X-ray diffraction, transmission, and field emission scanning electron microscopy (FESEM) were used to confirm the synthesis of the sorbent. The removal time, pH, and the sorbent dose were studied and optimized as the effective parameters on the As (V) removal.

The XRD, FTIR, TEM, SEM, EDS, and VSM techniques confirmed the properties of the synthesized magnetic bio-sorbent. Based on the optimization study, pH=6, the sorbent concentration of 30 mg, and the removal time of 5 minutes were considered as the optimum conditions with about 91% AS removal. The Langmuir isotherm with higher R2 value was matched well with the obtained results, and values obtained for qm and RL were 167 mg g–1 and 0.976 to 0.993, respectively. The kinetics studies were fitted well with the linear pseudo-first-order model with higher R2 at sorption process.

The real samples results confirmed the excellent As (V) sorption capacity of the synthesized magnetic bio-sorbent in comparison with other sorbents. Therefore, CLDH@Fe3O4@PA sorbent is introduced as a new suitable sorbent for removal of As (V) from the polluted water.

Dissolved air floatation (DAF) is one of the methods has been used for the sludge thickening in wastewater treatment plants. This study aimed to investigate the effects of coagulation and sonication processes as additional configurations on the efficiency of a lab-scale DAF process for thickening of the biological sludge of an industrial wastewater treatment plant in Kashan, Iran.

The required amounts of sludge samples were collected from a wastewater treatment plant and kept at temperature of 4°C. Variables, such as pressure (3, 5, and 7 atm), flotation time (5 and 10 minutes), ultrasonic irradiation power (0, 75, and 150 W), and presence/absence of Fe-based coagulant were considered on a sequencing batch reactor (SBR) included coagulation, flotation, and sonication processes, respectively.

The use of ultrasonic waves led to an insignificant increase in the DAF efficiency (P > 0.05), however, the application of coagulant significantly increased the thickening efficiency (P < 0.05). The maximum efficiency of the process was achieved at flotation time of 5 min, pressure of 3 atm, and sonication power of 75 W.

According to the results, DAF has a proper efficiency for thickening of biological sludge. Coagulation compared to sonication has a greater effect on the efficiency of the process.