Wastewater Treatment In Areas Research Articles

The production and application of carbon nanomaterials from high alkali silicate herbaceous biomass

Herein, value-added materials such as activated carbon and carbon nanotubes were synthesized from low-value Miscanthus × giganteus lignocellulosic biomass. A significant drawback of using Miscanthus in an energy application is the melting during the combustion due to its high alkali silicate content. An application of an alternative approach was proposed herein for synthesis of activated carbon from Miscanthus × giganteus, where the produced activated carbon possessed a high surface area and pore volume of 0.92 cm3.g−1 after two activation steps using phosphoric acid and potassium hydroxide. The SBET of the raw biomass, after first activation and second activation methods showed 17, 1142 and 1368 m2.g−1, respectively. Transforming this otherwise waste material into a useful product where its material properties can be utilized is an example of promoting the circular economy by valorising waste lignocellulosic biomass to widely sought-after high surface area activated carbon and subsequently, unconventional multi-walled carbon nanotubes. This was achieved when the activated carbon produced was mixed with nitrogen-based material and iron precursor, where it produced hydrophilic multi-wall carbon nanotubes with a contact angle of θ = 9.88°, compared to the raw biomass. synthesised materials were tested in heavy metal removal tests using a lead solution, where the maximum lead absorption was observed for sample AC-K, with a 90% removal capacity after the first hour of testing. The synthesis of these up-cycled materials can have potential opportunities in the areas of wastewater treatment or other activated carbon/carbon nanotube end uses with a rapid cycle time.

Quantifying water-energy nexus for urban water systems: A case study of Addis Ababa city

The complex interdependency between water and energy poses new challenges for policymakers to achieve a safe, secure, and sustainable supply of water and energy in the future. The water-energy nexus can be typically characterized by efficient use of energy and water resources. Hence, this paper aims to explore quantitative results of the nexus in terms of energy intensity on existing water systems within urban water cycles. The energy requirement for water treatment and water conveying to the city (from Legadadi water treatment, Gefersa water treatment and wastewater treatment area) as well as the energy requirement for water distribution within the city were quantified. The energy intensity for groundwater extraction, water transmission and water distribution were computed using Energy Intensity method. This led to identify the best technologies to insure the security of water-energy nexus. The annual energy demand and energy intensity values for groundwater extraction were estimated to be 0.6 PJ and 1.2 kWh/m3 respectively. These values for operating all pumps in the water transmission were 0.13 PJ and 0.32 kWh/m3 respectively. Similarly, the energy intensity value for water distribution was 0.27 kWh/m3 and distributes water to residential, commercial and industrial end-users. Determining the energy intensity predicts the future energy demand in urban water system. In 2030 and 2050, the predicted energy demand will be 0.50 and 0.83 PJ respectively for water transmission whereas it will be 0.41 and 0.67 PJ for water distribution.

Distribution Characteristics of Volatile Organic Compounds and Contribution to Ozone Formation in a Coking Wastewater Treatment Plant.

Ozone pollution, which can be caused by photochemical reactions, has become a serious problem. The ozone formation potential (OFP) is used to describe the photochemical reactivity. Volatile organic compounds (VOCs) are main precursors of ozone formation, and wastewater treatment plants (WWTPs) are important sources of VOCs. Therefore, it is necessary to study the concentration level and OFP of VOCs from WWTPs. In this work, a coking WWTP with anaerobic-oxic-oxic (A/O/O) processes in Shaoguan city, Guangdong province, China, was selected to investigate the characteristics of VOCs at wastewater treatment areas and office areas. The OFP of VOCs was estimated by the maximum incremental reactivity (MIR) coefficient method. Results showed that 17 VOCs were detected, and the total concentration of VOCs was the highest at the raw water tank (857.86 μg m−3). The benzene series accounted for 69.0%–86.9% and was the main component of VOCs in the WWTP. Based on OFP data, the top six VOCs contributing most to the OFP were m-xylene, toluene, p-xylene, o-xylene, styrene, and benzene. This study provides field data and information on the environmental risk of VOCs for coking companies and environmental departments. We found that the priority control sources of VOCs were wastewater treatment units because of their larger OFP contributions.

Evaluating Food Waste Handling Using Trios Monitoring System on Soy Industry in Bali, Indonesia

The purpose of this paper is to analyze a series of operational systems for biofilter technology. The object of research is an area of Wastewater Treatment in the food industry Denpasar, Bali. The Trios System Monitoring Method can be analyzed in three stages of the process of pre-treatment, treatment, stabilization, and three treatments. Biology analyzes settings (giving oxygen, feeding the number of food microorganisms F/M/ ratio, speed of waste flow). The analysis shows that biofilter technology is a technology that uses physical and biological treatment without using chemicals. Physical treatment is carried out by filtration, flotation, sedimentation. Biological treatment is carried out by regulating oxygen delivery with aeration period of 24 hours/day, microorganism feeding F/Mg/ BOD/MLSS/day ratio 0.05-0.2 with 100% proven waste flow BOD decreases by 80% pre-stage treatment. The wastewater is forwarded to the biofilter pond and given physical treatment, biological, and tricking filter in speed regulation, treatment process stage, liquid waste originating from conventional ponds is inserted into the aeration pond with aeration period of 6.0-9.0/hour. Feeding microorganisms F/Mg/BOD/day/MLSS ratio 0.2-0.5 with the waste flow 50%, BOD decreased by 85%. Feeding microorganisms F/Mg/BOD/day/MLSS ratio 0.2 - 0.5 oxygen administration with aeration period of 6.0-9.0/hour, BOD decreased by 85-90%.

Adsorption of Cu(II) ions from aqueous solutions on waste coffee residues: sorption kinetics, equilibrium isotherms, and thermodynamic parameters

Water polluted with metal ion is a serious environmental problem worldwide in recent years. Among various metal ions commonly found in wastewater, copper (II) is a priority toxic pollutant and needs to be removed Cu(II) from aquifers to mitigate water pollution. One possible way to clean Cu(II)-polluted water is the use of agricultural based low-cost adsorbent. Therefore, in this study, waste coffee residue (WCR) with four different morphologies has been used as adsorbents to adsorb Cu(II) from aqueous solutions. These adsorbents have been characterized using Fourier-Transform Infrared Spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) specific surface area (SSA), and point of zero charge (pHPZC) using zeta potential measurement. Batch Cu(II) adsorption data were evaluated in terms of adsorption edges, kinetics, isotherms, and thermodynamic calculations. Cu(II) adsorption was rapid and reached equilibrium within 60 min and strongly depended on solution pH. Adsorption data correlated with pseudo-second-order kinetic and Langmuir model satisfactorily. The maximum adsorption capacities for these adsorbents defined as WCR1, WCR2, WCR3, and WCR4 were 4.79, 8.04, 12.34, and 13.33 mg/g, respectively, at pH 5 and 25 °C. Thermodynamic calculations with WCR2 substrate revealed that Cu(II) adsorption was spontaneous and endothermic in nature. The result of this study shows that these adsorbents are efficient in removing Cu(II) and could be used to adsorb other pollutants from large scale environmental samples. This study could be a good contribution of the cleanup waste water and represents an active research in the area of waste water treatment by bio-adsorbent.

Upcycling brewer's spent grain waste into activated carbon and carbon nanotubes for energy and other applications via two‐stage activation

AbstractBACKGROUNDBrewer's Spent Grain (BSG), a form of lignocellulosic biomass more commonly known as barley waste was used to synthesize activated carbon (AC) and carbon nanotubes (CNTs). The produced materials were used in water remediation application.RESULTSA novel approach involving two activation steps; first, with phosphoric acid (designated BAC‐P) and then using potassium hydroxide (designated BAC‐K) was proposed for the production of AC and CNTs from BSG. The AC produced showed a surface area as high as 692.3 m2 g−1 with a pore volume of 0.44 cm3 g−1. This can help aid and facilitate the circular economy by effectively upcycling and valorizing waste lignocellulosic biomass to high surface area AC and subsequently, multi‐walled carbon nanotubes (MWCNTs). Consequently, MWCNTs were prepared from the produced AC by mixing it with the nitrogen (N)‐based material melamine and iron precursor, iron (III) oxalate hexahydrate, where it produced hydrophilic MWCNTs. Both AC and CNT materials were used in heavy metal removal (HMR), where the maximum lead absorption was observed for sample BAC‐K with 77% removal capacity after the first hour of testing.CONCLUSIONThis result signifies that the synthesis of these upcycled materials can have an application in the areas of wastewater treatment or other AC/CNT end uses with a rapid cycle time. © 2019 Society of Chemical Industry

Green technology innovation development in China in 1990–2015

Patent data present a number of advantages compared to other alternative measures of innovation. This paper presents research on the use of environmentally relevant technology patent data using a comprehensive analysis method to analyze the development of green technology innovation in China in 1990–2015. From the analysis, it can be concluded that during the period of 2000–2015, China's environmental-related technology innovation made great progress and was at the forefront of green technology growth; in particular, the areas of water and wastewater treatment, solar photovoltaic (PV) energy, lighting, improvements related to bulk or fine chemicals or pharmaceuticals, electric vehicles, and other technologies made great achievements. These technologies are closely related to environmental policies, such as climate change mitigation and green industry transformation, for which China has been advocating for more than a decade. However, after analyzing China's green development, it was found that, although some of the indicators, environmental-related patents, and green developments have made great progress, complete reliance on green technology is far off in the future.

ENVIRONMENTAL CONSIDERATIONS OF LARGE WASTEWATER TREATMENT PLANTS – THE CITY OF NIŠ CASE STUDY

Nowadays, the Republic of Serbia is at the bottom of the scale of European countries in terms of public utility equipment of the respective communal infrastructure particularly within the area of wastewater collection and treatment. The current situation in the area of water resources management in the Republic of Serbia indicates that the basic problems are insufficient construction of sewerage infrastructure in cities, i.e. insufficient coverage with the sewerage network of users connected to either public or private water supply network, followed by an insufficient number of constructed and operative wastewater treatment plants. In this sense, a particular problem is a requirement for relatively large initial investments in wastewater collection and treatment sector. Also, a special difficulty is the low price of delivered and channeled water within the existing system of public utilities, which is insufficient to provide maintenance of the existing water supply and sewage systems, regardless the future development and improvement of the existing system. Currently, only 10% of total produced wastewater quantity is treated in the Republic of Serbia, with different procedures and with uneven and, most often, insufficient purification effects. In addition to wastewater generated by the population (i.e. households connected to the sewer system), the special problem is the inadequate treatment of industrial wastewater. On the other hand, disposition of treated wastewater, disposal of separated sludge from the treatment process, odor and pest control, noise control, working conditions, etc. are significant challenges for the scientists, professionals and operators. Therefore, the aim of this paper is to comprehensively examine all environmental aspects on the example of a large wastewater treatment plant which is to be gained by the city of Niš, in the very near future.

Efficient Oil/Water Separation Membrane Derived from Super-Flexible and Superhydrophilic Core-Shell Organic/Inorganic Nanofibrous Architectures.

To address the worldwide oil and water separation issue, a novel approach was inspired by natural phenomena to synthesize superhydrophilic and underwater superoleophobic organic/inorganic nanofibrous membranes via a scale up fabrication approach. The synthesized membranes possess a delicate organic core of PVDF-HFP and an inorganic shell of a CuO nanosheet structure, which endows super-flexible properties owing to the merits of PVDF-HFP backbones, and superhydrophilic functions contributed by the extremely rough surface of a CuO nanosheet anchored on flexible PVDF-HFP. Such an organic core and inorganic shell architecture not only functionalizes membrane performance in terms of antifouling, high flux, and low energy consumption, but also extends the lifespan by enhancing its mechanical strength and alkaline resistance to broaden its applicability. The resultant membrane exhibits good oil/water separation efficiency higher than 99.7%, as well as excellent anti-fouling properties for various oil/water mixtures. Considering the intrinsic structural innovation and its integrated advantages, this core–shell nanofibrous membrane is believed to be promising for oil/water separation, and this facile approach is also easy for scaled up manufacturing of functional organic/inorganic nanofibrous membranes with insightful benefits for industrial wastewater treatment, sensors, energy production, and many other related areas.

Mercury Distribution Characteristics and Its Mass Balance in a Multifunctional Urban Wetland

The distribution characteristics and the source-sink relationship of total mercury (THg) and methyl mercury (MeHg) were studied in a wastewater treatment area and in a lake deep purification area of a multifunctional urban wetland that integrates domestic sewage treatment plant effluent, water purification, and leisure entertainment in Chongqing. The results showed that the THg concentration ranged from 1.98 ng·L-1 to 38.03 ng·L-1[average concentration was (9.10±5.84) ng·L-1] and MeHg concentration ranged from 0.09 ng·L-1 to 0.84 ng·L-1[average concentration was (0.34±0.08) ng·L-1] in an outlet of wastewater treatment area. In the deep purification zone, the THg concentration ranged from 0.37 ng·L-1 to 85.69 ng·L-1[average concentration of (6.76±2.29) ng·L-1] and the MeHg concentration ranged from 0.04 ng·L-1 to 1.47 ng·L-1[average concentration of (0.35±0.17) ng·L-1]. The interference of human activities on mercury concentration is prominent. The vertical distribution of THg in the water is consistent with that of MeHg, the surface layer has lower values than the deep layer. Material balance suggested that THg in the wetland system decreases by 155.50 g per year, and MeHg decreases by 1.65 g per year, which has a protective effect on the downstream water.

Advanced Design and Synthesis of Composite Photocatalysts for the Remediation of Wastewater: A Review

Serious water pollution and the exhausting of fossil resources have become worldwide urgent issues yet to be solved. Solar energy driving photocatalysis processes based on semiconductor catalysts is considered to be the most promising technique for the remediation of wastewater. However, the relatively low photocatalytic efficiency remains a critical limitation for the practical use of the photocatalysts. To solve this problem, numerous strategies have been developed for the preparation of advanced photocatalysts. Particularly, incorporating a semiconductor with various functional components from atoms to individual semiconductors or metals to form a composite catalyst have become a facile approach for the design of high-efficiency catalysts. Herein, the recent progress in the development of novel photocatalysts for wastewater treatment via various methods in the sight of composite techniques are systematically discussed. Moreover, a brief summary of the current challenges and an outlook for the development of composite photocatalysts in the area of wastewater treatment are provided.

Study of Sludge Particles Formed during Coagulation of Synthetic and Municipal Wastewater for Increasing the Sludge Dewatering Efficiency

Municipal wastewater sludge was produced by chemical coagulation of synthetic wastewater (sww) based on Synthene Scarlet P3GL disperse dye and real municipal wastewater (nww), coagulated by commercial coagulants PAX (prepolymerised aluminum coagulant) and PIX (a ferric coagulant based on Fe2(SO4)3). An attempt was made to correlate the sludge’s dewatering capacity (in terms of capillary suction time—CST) with operation parameters for wastewater treatment, size distribution and specific surface area of the sludge particles. It was found that the presence of phosphate ions in the system facilitates the removal efficiency of the above-mentioned dye (L) due to the interaction between the dye molecules and H2PO4− ions. Unlike sww, negatively charged organic substances (sorg) in nww are directly adsorbed on the surface of colloidal particles {Fe(OH)3} and {Al(OH)3} (prtc). It was also discovered that an increase in the dose of a coagulant led to an increase of CST for sww sludge and to a decrease of CST for nww sludge. It has been suggested that flocs composed of spherical {Al(OH)3} units possessed more internal space for water than aggregates consisting of rod-shaped {Fe(OH)3} units and, consequently, it is more difficult to remove water from Al-sww sludge than from Fe-sww. The results obtained showed that smaller particles dominate in sww sludge, while larger particles are prevalent in nww sludge. To explain this distinct difference in the size distribution of particles in sludge obtained with the use of Al3+ and Fe3+, simple models of aggregation and agglomeration-flocculation processes (aaf) of treated wastewater have been proposed. Except for PIX in nww, the analyzed particles of the investigated types of sludge were characterized by similar specific surface area (Sps), regardless of the kind of sludge or the applied coagulant. Slightly larger, negatively-charged sorg bridges, anchored directly on the surface of positive prtc are more effective in closing the structure of nww sludge than small L bridges of the dye molecules anchored on the surface of prtc via H2PO4−. All the discovered aspects could lead to improved performance of wastewater treatment plants (WWTP) by increasing the efficiency of sludge dewatering.

Investigation of soil and groundwater environment in urban area during post-industrial era: A case study of brownfield in Zhenjiang, Jiangsu Province, China

ABSTRACT With the adjustment of industrial structure, many high pollution enterprises will gradually shut down. This process will produce a large number of high-risk pollution plots and cause a series of environmental problems. In this study, geophysical detection and direct push technology were applied to investigate soil and groundwater pollution in a typical brownfield in Zhenjiang, Jiangsu province, China. The results showed that Chlorotoluene and its ramification were the main pollutants for the brownfield. Pollution decreased with depth and was quite uneven in the brownfield. Production and wastewater treatment areas were heavily polluted, where volatile organic compounds contaminated and semi-volatile organic compounds were found 12 m and 15 m below the land surface, respectively. About 18880 m3 groundwater was contaminated. This study is significant to develop a geological survey work mode for the postindustrial era.

Impact of the wastewater-mixing zone on attenuation of pharmaceuticals in natural waters: Implications for an impact zone inclusive environmental risk assessment

The direct discharge of untreated wastewater has been identified as an important source of environmental contamination by active pharmaceutical ingredients and other ‘down-the-drain’ chemicals in developing countries. It necessitates the development of an environmental risk assessment approach for the resulting impact zone. This study was designed to investigate the impact of low level of dilution (<10) on the natural attenuation processes of distribution and degradation within the impact zone. Dilution of the untreated wastewater resulted in increased desorption and corresponding environmental concentrations. The presence/absence of the microbial population in the batches affected the degree of sorption depending on the compound charge (i.e. positive or negative), highlighting an experimental technical bias. The degradation half-lives of acebutolol and diclofenac increased with increasing dilution and resulted in higher environmental persistence. The modelling of the biochemical oxygen demand (BOD) allowed an estimate of the temporal end boundary of the impact zone to be predicted as 24h. Therefore, it was concluded that most of the investigated compounds would persist beyond the end of the impact zone as defined by the return to environmental BOD concentrations. It is proposed that, within environmental risk assessment protocols, the impact zone should be considered as a semi-natural wastewater treatment area in such a way to allow the estimate of environmental concentrations of pharmaceuticals beyond its end.

Uptake Hazardous Dye from Wastewater Using Water Hyacinth as Bio-Adsorbent

The existing study demonstrates that water hyacinth (eichhorniacrassipes) is a potential adsorbent for the removal of Congo red dye from synthetic wastewater by batch process. The experiments were conducted to study the influence of various parameters such as initial dye concentration, pH, contact time and adsorbent dosage at different operating conditions. The effect of pH and dye concentration was found to be significant and the maximum removal was detected at pH 5 and concentration 100 ppm; considered to be optimum values. The removal of Congo red was consistent initially proportional to the adsorbent dosage. The adsorption process followed Langmuir adsorption isotherm model; point out that the process supported monolayer adsorption of Congo red on the adsorbent surface. Adsorption kinetics closely followed the pseudo-second-order model and mass transfer analysis indicated better transportation of adsorbate from solution phase to solid phase. These results point out suitability of the locally available low cost adsorbents in the niche area of wastewater treatment and can be implemented in commercial dye enriched industrial effluent.

Decolorization of Textile Wastewater Using Fabricated Poly Acrylonitrile (PAN) Nanoparticles

Water contamination is not only influence human health and environment, but it has alsoeffects on social and economic costs. Textile wastewater is considered to be one of the mostdangerous types of water contaminants as it consists of mixture of pigments, dyes and differenttypes of organic contaminants. Nanotechnology offers novel functional materials in the area ofwastewater treatment especially dye removal. Polyacrylonitrile (PAN) nanoparticles considered tobe one of the most promising prepared materials in the field of dye removal. PAN nanoparticleswas prepared by precipitation polymerization technique in an alcoholic aqueous solution (water:ethanol) and was characterized using scanning electron microscope (SEM), Fourier Transferinfrared spectrophotometer (FT-IR) and Thermal Gravimetric Analysis (TGA). Basic Red 46 (BR46) dye is a cationic dye which is used as a model of contaminant due to its extensive use intextile industry. The processing parameters affecting on the adsorption of BR 46 onto theprepared PAN nanoparticles have been optimized through a batch mode experiments.The maximum removal percentage of the selected dye was 62.4 % recorded after 240 minequilibrium time using 0.05 g from PAN nanoparticles and with 5 ppm initial dye concentration.As the experimental results proved that the increment in material dosage from 0.01 to 0.5 genhanced the dye removal percentage from 43.6% up to 85%. Meanwhile, the improvement ininitial dye concentrations had negative impact on the adsorption process onto the preparedpowdered material, as it decreased from 82.3 to 11.85% when the initial dye concentrationincreased from 1-100 ppm. The dye adsorption mechanism was investigated through theapplication of Langmuir and Freundlich isotherm models on the experimental data. Moreover, thekinetics of dye adsorption process was tested using the pseudo-first and pseudo-second orderkinetic models.

Development of Aerobic Granular Sludge for Chemical Industries Wastewater Treatment

Background: The world’s chemical industries are confronted with formidable environmental regulatory challenges in treating their wastewaters. Aerobic granulation is increasingly drawing interest of researchers engaging work in the area of biological wastewater treatment. Objectives: The objective is to develop a new cost-effective technique for treatment of chemical industry effluents. The possibility and effectiveness of this new enhanced biological treatment system were determined through mean diameter, relative hydrophobicity, sphericity, and sludge volume index (SVI5) of aerobic microbial aggregates. Scanning electron microscopy (SEM) analysis was also used to characterize the granules. Methods: The granules were cultivated in a single sequencing batch reactor (SBR) system fed with synthetic ethylene glycol (MEG) wastewater. The characteristics of the aerobic granular sludge were monitored during the study period. Results: Aerobic granules with dense and strong microbial structure as well as excellent settling ability were cultivated. Developed granules had an average size of 8.21 ± 2 mm. The process of granulation resulted in an increased biomass concentration from about 2500 to 4750 mg/L. The microbial granular sludge was able to remove 97% of the influent COD at organic loading rate (OLR) of 2.0 kg COD/m3.day, at the end of the study. Conclusions: The findings of the present study revealed that aerobic granular sludge could be successfully developed in a SBR and is capable in treating the simulated chemical industries wastewater.

Selective adsorption and degradation of organic pollutants over Au decorated Co doped titanate nanotubes under simulated solar light irradiation

Abstract Au decorated Co doped titanate nanotubes (TNT) was prepared for selective removal of methylene blue (MB) dye followed by selective photocatalytic degradation under solar light in presence of another highly concentrated dyes. The adsorption capacity of Co doped TNT was found to be increased with increasing Co content due to the increase in the number of pores and thus increase in surface area. Due to the high concentration of MB, Co doped TNT was completely covered by MB molecules and become difficult for light to Path though or absorbed by the Co doped TNT catalyst. In order to provide some photocatalytic characteristics for the catalyst, the doped TNTs were calcined to enhance the crystallinity and thus enhancing the photocatalytic activity, but the degradation rate was very low. Thus, another direction was started by reducing the adsorption ability of Co doped TNT through coating its surface by poly(allylamine hydrochloride), which changed the surface charge of the tubes to be positive and facilitate the electrostatic attachment of Au nanoparticles (15 nm). The synergetic effect of plasmonic Au nanoparticles in addition to adsorption and catalytic properties of Co doped TNT make the new composite promising catalyst for degradation of organic pollutants. It shows a good selectivity for adsorption and photocatalytic degradation of MB dye from dyes mixture. The obtained results indicate that Au decorated Co doped TNT will have a great effect on the development of selective environmental water treatment technologies specifically on flow challenges confronted by the wastewater treatment area.

Adsorption of Congo red from aqueous solution onto shrimp shell powder

Two novel adsorbents derived from shrimp shell were prepared and their adsorption performances on Congo red were investigated. The results suggested that treated shrimp shell powder exhibited a higher adsorption capacity than raw shrimp shell powder. The factors of initial concentration, solution pH, adsorption time, and temperature were investigated. The maximum adsorption capacity of treated shrimp shell powder calculated according to the Langmuir isotherm model was 288.2 mg/g, which is much higher than that of chitin. The adsorption behavior could be fitted well by the pseudo-second-order kinetic model. Intra-particle diffusion model was also used to study the adsorption process. The thermodynamic parameters indicated the spontaneous and endothermic nature of the adsorption. Shrimp shell powder exhibited enough advantages such as large adsorption capacity, low cost, simple processing methods and high specific gravity compared with chitin or chitosan. This work confirmed that the shrimp shell biosorbent had a potential to be applied in dye wastewater treatment area.

Emission and health risk assessment of volatile organic compounds in various processes of a petroleum refinery in the Pearl River Delta, China

The process-specific emission of volatile organic compounds (VOCs) from a petroleum refinery in the Pearl River Delta, China was monitored to assess the health risk from VOCs to workers of this refinery. Over 60 VOCs were detected in the air samples collected from various sites in the refining, basic chemical, and wastewater treatment areas of the refinery using gas chromatography-mass spectrometry/flame ionization detection. The health risks of VOCs to the refinery workers were assessed using US Environmental Protection Agency (US EPA) and American Conference of Governmental Industrial Hygienists (ACGIH) methods. Monte Carlo simulation and sensitivity analysis were implemented to assess the uncertainty of the health risk estimation. The emission results showed that C5-C6 alkanes, including 2-methylpentane (17.6%), 2,3-dimethylbutane (15.4%) and 3-methylpentane (7.7%), were the major VOCs in the refining area. p-Diethylbenzene (9.3%), 2-methylpentane (8.1%) and m-diethylbenzene (6.8%) were dominant in the basic chemical area, and 2-methylpentane (20.9%), 2,3-dimethylbutane (11.4%) and 3-methylpentane (6.5%) were the most abundant in the wastewater treatment area. For the non-cancer risk estimated using the US EPA method, the total hazard ratio in the basic chemical area was the highest (3.1 × 103), owing to the highest level of total concentration of VOCs. For the cancer risk, the total cancer risks were very high, ranging from 2.93 × 10−3 (in the wastewater treatment area) to 1.1 × 10−2 (in the basic chemical area), suggesting a definite risk. Using the ACGIH method, the total occupational exposure cancer risks of VOCs in the basic chemical area were the highest, being much higher than those of refining and wastewater treatment areas. Among the areas, the total occupational exposure risks in the basic chemical and refining areas were >1, which suggested a cancer threat to workers in these areas. Sensitivity analysis suggested that improving the accuracy of VOC concentrations themselves in future research would advance the health risk assessment.