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Treatment and Recycling of Wastewater from Oil Refinery/Petroleum Industry
Abstract
Petroleum refinery effluents (PRE) are generally the wastes generated from industries primarily engaged in refining crude oil, manufacturing fuels, lubricants and petrochemical intermediates. These effluents or wastewater, generated, are considered as a major source of aquatic environmental pollution. The effluents are mainly composed of oil, grease and many other toxic organic compounds. The process of crude oil refining consumes large volume of water. Consequently, significant volume of wastewater is generated. The requirement of water depends upon on the size, crude products and complexity of operation. Petroleum refining units need water for distillation, desalting, thermal cracking, catalytic and treatment processes in order to produce useful products such as LPG (Liquefied Petroleum Gas), gasoline, asphalt, diesel, jet fuel, petroleum feedstock etc. Wastewater generated through petroleum refineries contains various hydrocarbons. It has been estimated that the demand for world oil is expected to rise to 107 mbpd (million barrels per day) in the next two decades. By 2030 oil will account for 32% of the world’s energy supply. The increasing demand of oil clearly shows that effluents produced from the oil industry will continue to be produced and discharged into the water bodies. The pollutants found in the effluent are seriously toxic and hazardous to the environment. Techniques used for effluent treatment include adsorption, coagulation, chemical oxidation, biological techniques as well as contemporary technologies like membranes and microwave-assisted catalytic wet air oxidation and Advanced oxidation processes (AOP) like heterogeneous photo-catalytic degradation which is based on its potential to completely mineralize the organic effluents beside being cost effective, readily available and the catalyst used itself is non-toxic in nature. The review provides a detailed description on nature of effluent or wastewater produced from the oil refinery units, its discharge into the water bodies, toxicological effects of the effluent on terrestrial and aquatic ecosystem and the various treatment technologies designed for the treatment and recycling of wastewater generated during operation.
... A significant amount of steam is used in the distillation unit; resulting vapours get condensed that contain hydrocarbons products, hydrogen sulphide, ammonia, etc. (EI-Nass et al., 2014). Distillation unit produces sour water, usually contaminated with ammonia, chlorides, phenol, hydrogen sulphide, mercaptans, and suspended solids (Singh, 2019). ...
... The products, namely kerosene, naphtha, and vacuum gas oil are treated in kerosene/ATF hydrotreating unit (KHTU), naphtha hydrotreating unit (NHTU), diesel hydrotreating unit (DHDT), and vacuum gas oil hydrotreating unit (VGO HDT), respectively. Hydrotreating units produce sour water that contains suspended solids, hydrogen sulphide and phenol (Fasihi et al., 2020;Singh, 2019). ...
... The process is conducted in the presence of hydrogen using metal catalyst (e.g., aluminium chloride activated with hydrochloric acid) at low temperature. This process generates caustic wash water (contain calcium chloride) and sour water (contain ammonia and hydrogen sulphide) (Singh, 2019). ...
Petroleum refinery wastewater (PRW) is a complex mixture of hydrocarbons, sulphides, ammonia, oils, suspended and dissolved solids, and heavy metals. As these pollutants are toxic and recalcitrant, it is essential to address the above issue with efficient, economical, and eco-friendly technologies. In this review, initially, an overview of the characteristics of wastewater discharged from different petroleum refinery units is discussed. Further, various pre-treatment and post-treatment strategies for complex PRW are introduced. A segregated approach has been proposed to treat the crude desalting, sour, spent caustic, and oily wastewater of petroleum refineries. The combined systems (e.g., ozonation + moving bed biofilm reactor and photocatalysis + packed bed biofilm reactor) for the treatment of low biodegradability index wastewater (BOD5/COD < 0.2) were discussed to construct a perspective map and implement the proposed system efficiently. The economic, toxicity, and biodegradability aspects are also introduced, along with research gaps and future scope.
... The anaerobic bioreactor joins the sedimentation of solids and their deposit in the base, with the floating material of the WWTP and the suspended active biomass. Both bottom mud and floating material provide adequate space for microbial growth [77,79] This type of bioreactor generates sludge and microbial biomass as residual products which are treated for reuse before leaving [80,81]. This method has indicated good efficiency in eliminating drugs of abuse at low concentrations, but in recent studies it has been accompanied by chlorination and maturation in ponds in order to allow better removal of drugs of abuse and their metabolites from WWTP [77,82,83]. ...
... The anaerobic bioreactor joins the sedimentation of solids and their deposit in the base, with the floating material of the WWTP and the suspended active biomass. Both bottom mud and floating material provide adequate space for microbial growth [77,79]. This type of bioreactor generates sludge and microbial biomass as residual products, which are treated for reuse before leaving [80,81]. ...
METHs are drugs that enter wastewater through the feces and urine of users. Conventional wastewater treatment plants are not capable of removing this type of emerging contaminant, but, in recent years, techniques have been developed to abate drugs of abuse. The present investigation focused on obtaining the technique that keeps the best balance between the comparison criteria considered: efficiency; costs; development stage; and waste generation. That is why a bibliographic review was carried out in the scientific databases of the last eight years, concluding that the six most popular techniques are: SBR, Fenton reaction, mixed-flow bioreactor, ozonation, photocatalysis, and UV disinfection. Subsequently, the Saaty and Modified Saaty methods were applied, obtaining a polynomial equation containing the four comparison criteria for the evaluation of the techniques. It is concluded that the UV disinfection method is the one with the best relationship between the analyzed criteria, reaching a score of 0.8591/1, followed by the Fenton method with a score of 0.6925/1. This research work constitutes a practical and easy-to-use tool for decision-makers, since it allows finding an optimal treatment for the abatement of METHs.
... Shailja Singh and Shikha [22] mentioned the primary pollutants found in the effluent from various processes in refineries. The liquid effluents generated in the oil refineries differ from one industrial plant to another due to the variation in the configuration of the plant and in particular, to the type of petroleum processed. ...
... The addition of H 2 O 2 to the system improves the production rate of hydroxyl radicals, as shown in Section 3.4.1, according to Equation (22). This system is similar to the UV-hydrogen peroxide system. ...
Sulfur compounds are removed from petroleum by the addition of sodium hydroxide at a very high concentration. As a result, a residue called spent soda or spent caustic is generated, being extremely aggressive to the environment. In this work, the chemical properties of this residue are described in detail. The sodium hydroxide remains that have not reacted, sulfur compounds, and organic matter are the primary pollutants reported. Additionally, the main characteristics of the methods of treatment used to reduce them are described. This review comes from comprehensive and updated research and bibliographic analysis about the investigation on the topic. The advantages and disadvantages of the different treatment methods are highlighted. We established some criteria to set out when assessing the application of each one of these treatments is considered.
... Overall, oxidative stress is higher in nestlings residing near highintensity industry and agriculture: Slavonski Brod-east and Podunavlje, respectively. The highest ROS production was detected in Refinery effluents usually consist of heavy metals and polycyclic aromatic compounds (PAHs) that can cause oxidative stress by increasing the production of ROS (Custer et al., 2000;Koivula & Eeva, 2010;Singh & Shikha, 2019). According to the annual report on Water Quality Status of Croatian Surface Waters (Musić et al., 2020) higher concentration on fluoranthene, a PAH pollutant and known carcinogen on the Candidate List of Substances of Very High Concern due to its persistent and bioaccumulative properties (Lotufo, 1998), was recorded in the vicinity of the sampled areas. ...
White stork nestlings can provide quantitative data on the quality of the environment, as they are dependent on their parents that provide locally foraged food. Blood was sampled from the brachial vein (n = 109) and the sampling was performed in parallel with ringing during breeding season 2020 from five areas in eastern Croatia: Lonjsko polje, Jelas polje, Slavonski Brod-east, Podunavlje, and Donje Podravlje. In the present study, for the first time in Croatia, the following enzymatic biomarkers were assessed in white stork nestlings: activities of acetylcholinesterase (AChE), carboxylesterase (CES), glutathione S-transferase (GST), and glutathione reductase (GR), as well as nonenzymatic biomarkers: levels of glutathione (GSH) and reactive oxygen species (ROS). All endpoints were measured in two blood fractions: plasma and a postmitochondrial fraction (S9). Nestlings from Podunavlje and Donje Podravlje, areas known for intensive agriculture, showed lower AChE and CES activity when compared to the other investigated areas, indicating the presence of inhibitory xenobiotics. Higher oxidative stress was observed in Slavonski Brod-east, an area surrounded by metal and engineering industry, and Podunavlje compared to the other sampling areas. Hence, this study shows the impact of pollutants from the surrounding metal, petroleum, and agricultural industry might have on the biomarkers in white stork nestlings, which are often seen as early-warning signals.
... Refineries' liquid effluents are complex matrices of organic and inorganic pollutants; the quantitative and qualitative contamination depends on the unit configuration and the crude oil nature. The major pollutants found in the effluent are oil and greases, which are the source for other hazardous compounds such as phenols, BTEX, naphthenic acids (NA) and poly-aromatic hydrocarbons (PAH) (Fakhru'l-Razi et al. 2009;Aljuboury et al. 2017;Ali et al. 2018;Al-Khalid & El-Naas 2018;Singh & Shikha 2019). ...
A synthetic wastewater based on Algiers refinery real effluent was prepared and treated using anodic oxidation. Full factorial plan design was used to conduct the statistical analysis of the results. The aim of the study was to assess the interaction between current density (CD) and stirring degree (SD), and quantify their effects on chemical oxygen demand (COD) removal and electric energy specific consumption (EESC). With an initial COD of 487 mg/L, pH of 5.5 and 0.05 M of Na2SO4 as supporting electrolyte, it was found that a 55 rpm stirring degree variation led to a substantial gain in COD removal and energy consumption: 6% and 8.5 KWh/kg, respectively. Current density was found to have a different effect on removal efficiency within the applied stirring domain, and mass transport coefficient (km) is inversely correlated to energy consumption. A theoretical model describing the process was reviewed and the relation between concentration, hydrodynamics and applied current was emphasized. HIGHLIGHTS
A simple empirical modeling to assess charge rate and mass transport rate balance (i.e. operating regime).;
Lead anode was first applied for electro-oxidation of toluene.;
Perspectives on the up-scaling approach taken and comparative data were discussed.;
Theoretical modeling review.;
... Therefore, a large amount of wastewater containing toxic organic compounds, grease and oil is generated in these companies. The results of the researches demonstrate that the generated wastewater is 0.4-1.6 times the amount of the proceed oils [12,13]. Despite to the efforts have been performed in recent years to replace the fossil fuels with appropriate alternative, the crude oil is known as an important raw material for different processes. ...
Numerous studies have indicated that the extraction of hydrocarbons from the subsurface is accompanied by the production of large volumes of solid and liquid wastes. An increasing body of literature suggests that various hazards and risks are intrinsic to both exploration and production operations. Waste management is one of the most critical factors controlling environmental pollution and safety in hydrocarbon exploration and production fields. The presence of oily materials in the waste makes it a potential environmental pollutant if not properly handled. Overall, the oil and gas industry operates in the most hazardous of situations and conditions. Nonetheless, it is necessary to maintain controlled working conditions. While some waste handling practices are adopted in some regions, some factors such as geological, economical, and environmental regulations require a unique set of waste management options. A suitable and smart waste management model should be designed to accommodate even the least environmental impacts with technical and economic feasibility. Artificial intelligence and expert systems provide new opportunities for harnessing the scarce and often scattered pieces of valuable knowledge and experience in solid waste management, which at present is in possession of the privileged few. This study evaluates the gaps in expert systems in oil and gas waste management and disposal. Expert systems are poised to take over the no-less essential tasks of the ill-structured and less-deterministic parts of the planning, design, and management processes concerning oil and gas waste management. There are two primary sources for wastes of resources for waste management systems: under usage of raw materials, which result in inaccurate predictions of desired outputs, and overuse of resources that arise because the necessary information would have been acquired from other sources. These irregularities lead to waste of resources, such as human, machine, and time that have tremendous implications on cost, availability, and human resources. A framework to address these challenges is proposed, and a systematic review of the literature was carried out to examine current oil and gas industry waste management technologies and research to determine and highlight how they can support these expert systems. This study shows the technical limitations and also reveals a variety of oil and gas waste measurement, collection, and conversion technologies that can be integrated through the application of internet-of-things. This chapter introduced and explained waste management systems in the oil and gas industry as well as detailed a composite network of corporate integration methods for solid and liquid waste management. Furthermore, suggestions on how to ensure the implementation of an efficient waste management scheme were discussed in order to overcome potential barriers to their performance.
Petroleum and petrochemical wastewaters are characterized by toxic organic pollutants, hydrocarbons, heavy metals, sulfur compounds, and refractory compounds. These pollutants are a potential threat to the environment if discharged without proper treatment. Therefore, the primary focus of wastewater treatment is to safeguard environmental and public health through their removal. Increasingly, sustainability is becoming an important decision-making criterion. Sustainability is a comprehensive terminology that involves environmental, economical, and social feasibility. Various techniques are available to treat petroleum and petrochemical wastewaters, depending on discharge requirements, capital and operating cost limitations, and other considerations. In this chapter, various methods for the treatment of petroleum and petrochemical wastewater are explored within the framework of sustainability and life cycle assessment, with a focus on wider environmental burdens and subsequent tradeoffs. As petroleum and petrochemical wastewaters contain water, energy, carbon, nutrients, salts, and heavy metals, it is emphasized that the modern wastewater treatment system should transform from “only treatment” to “resource recovery and treatment.” Such transformation requires careful consideration of impacts and benefits of resource recovery processes and outputs, both to the petroleum/petrochemical companies and the industries and end-users well outside the typical wastewater plant boundary.
The separation of oily wastewater, especially emulsified oil/water mixtures, is a worldwide challenge because of the large amount of oily wastewater produced in many industrial processes and daily life. For the treatment of oily wastewater, membrane technology is considered the most efficient method because of its high separation efficiency and relatively simple operational process. In this short review, the recent development of advanced filtration membranes for emulsified oil/water mixture separation is presented. We provide an overview on both traditional filtration membranes, including polymer-dominated and ceramic-based filtration membranes, and recently developed nanomaterial-based functional filtration membranes, especially one-dimensional nanomaterials, for effectively treating emulsified oil/water mixtures. The liquid flux and antifouling property, which are the most important factors for membrane performance evaluation, are described for different types of membranes. Conclusions and perspectives concerning the future development of filtration membranes are also provided.
The ability of three bacterial isolates (Bacillus spp, Micrococcus spp and Proteus spp.) and some fungal species (Penicillin spp., Aspergillus spp. and Rhizopus spp.) isolated from two rivers and refinery effluent to degrade two Nigerian Crude oils was studied. The results showed changes in pH, optical density and total viable count for the bacterial isolates after a 17-day period. There was an increase in biomass for the fungal isolates after a 35-day period. It was observed that these organisms were able to utilize and degrade the crude oil constituents, with bacterial isolates showing increase in cell number and optical density as pH decreases. Single cultures were observed to be better crude oil degraders than the mixed cultures (bacteria or fungi). It was also observed that oil degraders could be isolated from a non-oil polluted environment, although those from oil-polluted environments have higher degradation potentials.
This review presents biological treatment methods for petroleum refinery wastewater, their applications, advantages and disadvantages. It covers refinery wastewater characteristics, different categories of biological treatment systems (suspended, attached and hybrid growths) and comparison between each system with conventional activated sludge process. Introduction Petroleum refining utilize large quantities of water for desalting, distillation, thermal cracking, catalytic and treatment processes to produce useful products [liquefied petroleum gas (LPG), gasoline, jet fuel, diesel, asphalt and petrochemical feedstock] 1-3 . Refining process generates wastewater (0.4-1.6 times the volume of crude oil processed) 4 . Discharge of untreated petroleum refining wastewater (PRW) into water bodies results in environmental and human health effects due to release of toxic contaminants (hydrocarbons, phenol and dissolved minerals) 5,6 . Hydrocarbons [benzene, toluene, ethyl benzene and xylenes (BTEX)] are of serious concern due to their toxicity and as carcinogenic compounds 3,7,8 . High exposure for long periods to these compounds can cause leukemia and tumors in multiple organs 3 . Phenol and dissolved minerals are also toxic to aquatic life and lead to liver, lung, kidney and vascular system infection 9,10 . Therefore, according to Environmental Protection Agency (USEPA), PRW have to be sufficiently treated for quality to meet the established regulations 11 . Physical and chemical treatments of PRW have been carried out using different methods [electrocoagulation (93% of sulfate and 63% of COD removal) 12 , electrochemical oxidation (92.8% for COD removal and low salinity of 84µScm -13 and dissolved air flotation (BOD and COD removal efficiencies of 76-94% and 72-92.5% respectively) 14 ]. However, physical and chemical methods are costly due to high price of chemicals and equipments, and excessive amounts of sludge production. Thus, biological methods are preferred due to simple, cheap and environmentally friendly operations 3,15 . This review presents characteristics of PRW and biological treatment technologies. Characteristics of Petroleum Refinery Wastewater (PRW) Crude oil contains various organic and inorganic compounds including salts, suspended solids and water-soluble metals. It undergoes desalting process as a first step to remove contaminants using large quantities of water; the process causes corrosion, plugging and fouling of equipment 16 . Composition of PRW depends on complexity of refining process 17 but in general, compounds in PRW include dissolved and dispersed oil and dissolved formation minerals 18 . Oil (Table 1) 4,19-21 is a mixture of hydrocarbons [benzene, toluene, ethylbenzene, xylenes, polyaromatic hydrocarbons (PAHs) and phenol]. While, dissolved formation minerals are inorganic compounds, which include anions and cations including heavy metals 18 .
Emulsified oil in waste water constitutes is a severe problem in the different treatment stages before disposed off in a manner that does not violate environmental criteria. One commonly used technique for remediation of petroleum contaminated water is adsorption. The main objective of this study is to examine the removal of oil from oil–water emulsions by adsorption on bentonite, powdered activated carbon (PAC) and deposited carbon (DC). The results gave evidence of the ability of the adsorbents to adsorb oil and that the adsorptive property of the three adsorbents (bentonite, PAC, and DC) has been influenced by different factors. The effects of contact time, the weight of adsorbents and the concentration of adsorbate on the oil adsorption have been studied. Oil removal percentages increase with increasing contact time and the weight of adsorbents, and decrease with increasing the concentration of adsorbate. Equilibrium studies show that the Freunlich isotherm was the best fit isotherm for oil removal by bentonite, PAC, and DC. The data show higher adsorptive capacities by DC and bentonite compared to the PAC.
During the production of petroleum and gas a by-product, known as congenital water, is obtained, which varies in composition depending on the geological formation from which it is extracted. In the industrial process its composition is modified and then it is known as “produced water”. These waters can contain high concentrations of mineral salts that can potentially be used for crop fertilization. The aim of this study was to evaluate the effects of the application of produced water on the mineral contents of the plants and levels of BTEX and TPH in the fruits of greenhouse tomato cultivation. The produced waters used were derived from gas producing zone of Sabinas-Piedras Negras in northern Mexico. These waters were analyzed according to NOM-143-SEMARNAT-2003. Waters from three different stations, (Buena Suerte, Forasteros and Monclova 1), were mixed with fresh water to obtain the treatment waters used. As a control, we used a complete Steiner solution. The results showed that the produced waters modified the absorption of essential minerals in tomato plants; it was observed that the mineral concentration in plant tissues was highest in the control plants, except for Na, in which the plants irrigated with produced water had the highest concentrations. The treatments with produced waters also affected negatively the root length, leaf dry weight, stem dry weight, number of fruits per plant, and the dry weight of the fruits.
Intensive industrialization generates hazardous wastes comprising organics, inorganics, heavy metals, and munitions that need to be tackled in a safe manner. Commonly employed physicochemical technologies have paved the way to ecofriendly bioremediation processes. Bioremediation uses natural as well as recombinant microorganisms to break down toxic and hazardous substances by aerobic and anaerobic means. They can be applied on site (in situ) or off site (ex situ), mediated by mixed microbial consortia and/or pure microbial strains and. plants (phytoremediation) or even natural attenuation. They include several processes - bioventing, biosparging, biostimulation, bioaugmentation, bioleaching, fungal bioremediation, and biosorption. Bioremediation also encompasses ex situ engineered methods like bioreactors and enzyme catalyzed breakdown. The success of bioremediation is governed by three important factors-availability of microbes, accessibility of contaminants, and a conducive environment. This review discusses various bioremediation technologies, listing the advantages as well as disadvantages and field application, if any.
Crude oil and condensate refineries generate a large amount of wastewater that has both process and non-process origins. Depending on the type of crude oil, composition of condensate and treatment processes, the characteristics of refinery wastewater vary according to a complex pattern. The design and operation of modern refinery wastewater treatment plants are challenging and are essentially technology driven. In this investigation, the sources of wastewater pollutants have been traced to specific sources and operations, and suitable treatment technologies identified. Modern powerful tools such image analysis have been employed to characterize oil droplet sizes in oily wastewater and immobilized cell technology considered in biological reactor design for wide spectrum chemical pollutant degradation. A biomass extraction method was developed to harvest Pseudomonas P. and Baccili S. cells from a commercial biological product and acclimate them to a source of carbon rich in phenol, prior to immobilizing them in a suitable gel.
The treatment of oil-in-water emulsions containing n-octane (used as simulated wastewater) was investigated by means of dissolved-air flotation jar-tests. The effect of several parameters on flotation efficiency for separation of the emulsified oil was examined, namely, (a) the presence the nonionic surfactant Tween 80, used for the stabilization of the emulsions, (b) the initial pH value of the emulsions, (c) the concentration of chemical additives, such as polyelectrolytes (organic flocculants of cationic or anionic type) or ferric chloride (inorganic coagulant), (d) the concentration of sodium oleate (used as flotation collector) and (e) the recycle ratio. Zeta-potential measurements were also performed in order to interpret the obtained results. The use of polyelectrolytes was not able to effectively treat the studied emulsions, while the addition of ferric chloride and the subsequent application of dissolved-air flotation was found very efficient. At the optimum defined experimental conditions (recycle ratio: 30%, pH: 6, [Fe3+]: 100 mg l−1 and [sodium oleate]: 50 mg l−1) more than 95% of the emulsified oil was effectively separated from an initial concentration of 500 mg l−1.
Experiments were carried out to evaluate the batch adsorption of phenol from petroleum refinery wastewater on a locally prepared date-pit activated carbon (DP-AC). Adsorption equilibrium and kinetics data were determined for the uptake of phenol from real refinery wastewater and from synthetically prepared aqueous phenol solution. The data were fitted to several adsorption isotherm and kinetics models. Sips as well as Langmuir models gave the best fit for equilibrium isotherms, whereas the kinetics data were best fitted by the pseudo-second order model. The enthalpy of adsorption showed an exothermic nature of the adsorption process. Several chemical and thermal techniques were tested for the regeneration of saturated activated carbon; using ethanol was found to be the most effective with more than 86% regeneration efficiency after four regeneration cycles.
Petroleum refineries release wastewater, which is rich in organic pollutants and cannot be treated easily. This study presents the treatment of petroleum refinery wastewater using nanoscale zero valent iron (NZVI) in the presence of ultrasonication. NZVI characteristics were analyzed using SEM and XRD. The influence of NZVI dosage and initial pH on % chemical oxygen demand (COD) reduction was studied. From the results, it can be inferred that a dosage of 0.15 g/l and an initial pH are optimum for the effective degradation of effluents. The degradation data were found to follow first order kinetics. The results indicate that using NZVI in combination with ultrasonication is an efficient method for the treatment of petroleum refinery wastewater.
In an effort at developing an active indigenous bacterial consortium that could be of relevance in bioremediation of petroleum contaminated systems in Nigeria, four hydrocarbon degrading bacteria strains were isolated. Partial sequencing of the 16S rDNA of the isolates suggests that they are all strains of Pseudomonas aeruginosa . Axenic cultures of the isolates biodegraded Bonny light crude oil in soil microcosm. Amount of crude oil biodegraded in 15 days ranged significantly (P < 0.05) from 4.9% to 29.6%. Degradation rates and specific growth rates varied significantly (P < 0.05) between 0.049 and 0.351 day-1 and 0.017 and 0.028 hour-1 respectively. Major peak components of the oil were reduced by between 6.5% and 70.6%. It would appear that oil degradation capability of axenic cultures of at least three of these isolates was not different from that of their consortium. Also, the multiple antibiotic resistance observed in the isolates is an important factor to consider in their eventual use in bioremediation exercises.
Phormidium bohneri, a self-flocculating cyanobacterium, was grown outdoors in a 75 l intensive culture basin (semi-continuous system) and used for the tertiary treatment of domestic wastewater. The behavior, growth and purification potential of P. bohneri were studied. The nutrient removal efficiency (max.: N(i) = 83%, 12.5 mg N l-1 d-1; P(i) = 81%, 1.3 mg P l-1 d-2) of this process allows a quite rapid treatment of the secondary effluent (hydraulic retention time = 1d). Stripping account for about 62% of nitrogen (NH3) removal while 38% is assimilated by P. bohneri. Inorganic phosphorus is removed mainly by precipitation (57%) and to a lesser extent is taken-up by Phormidium (43%). The cyanobacterial biomass (P: 1.1%, N: 8.6%, protein: 53.5%, dry weight basis) can be easily harvested after the treatment by settling.
In the present work, Triacylglycerin lipase (Aspergillus niger lipase) was immobilized on chitosan, celite and cellulose acetate polymer structure by adsorption. The concentration of protein in lipase solution before and after immobilization was determined by using the Lowry’s method and analyzed using UV-Spectrophotometer. After 12 h, the protein yield percentage of lipase on chitosan, celite and cellulose acetate support were 93.7%, 90.2% and 87.3%. Surface characterization of immobilized lipase was determined by using optical microscopy. Chitosan immobilized lipase bead (most suitable) from A. niger bead was used for removal of oil and grease (O&G) from synthetic oily water with bead concentration of 0.1–0.3 g/l. Approximately 48% of the O&G was hydrolyzed by 0.3 g/l bead of chitosan immobilized lipase from A. niger. In addition, about 47% reduction in COD was estimated after degradation of synthetic oily water with chitosan immobilized lipase.
Increasing emission of greenhouse gases intensifies global warming. To tackle the problem, major economies in the world need to implement policy on energy saving. The wastewater treatment industry, being one of the energy consumers, has developed various technologies to improve energy efficiency and has started to use renewable energy with the aim of achieving energy neutrality in the wastewater treatment process. A literature review found that there is a series of energy-saving methods that can reduce the electricity consumption by 20% in wastewater treatment. Majority of the energy saving comes from energy conservation measures in pumping and aeration systems. In wastewater treatment works, two kinds of renewable energy are usually available, namely solar energy and biogas. The recent development of photovoltaic cells makes it a more practical and financially viable energy source which may cover 40% of the electricity consumption of a wastewater treatment works. Biogas, a by-product generated from the anaerobic digestion process in a wastewater treatment works, can also generate 40% of the electricity required. To achieve energy neutrality, the remaining electricity consumption can be generated through co-digestion of wastewater sludge and organic fraction in municipal solid waste.
The objectives of oil and gas produced water treatment include meeting discharge regulations (local, state and federal), reusing treated produced water in oil and gas operations, developing agricultural water uses, rangeland restoration, cattle and animal drinking water, water for human consumption, and meeting water quality requirements for miscellaneous beneficial uses. Current produced water technologies and their successful applications have advantages and disadvantages and can be ranked on the basis of those factors. This paper attempts to describe, summarize and analyze various produced water treatment systems developed by oil and gas producers, research organizations, water treatment service companies, and universities. Treatment technologies, furthermore, have applicability to different kinds of produced water from strong brines to brackish waters.
This paper reports on biological treatment by activated sludge of petroleum refinery wastewaters, in a lab-scale reactor constituted by an aeration tank and clarifier provided with sludge recycle system. The main objective of the work includes the optimization of the process efficiency in terms of chemical oxygen demand (COD), total organic carbon (TOC), and total suspended solids (TSS), and modeling of the biological treatment by activated sludge and determination of the main stoichiometry and kinetic parameters for the process, such as, synthesis and decay of biomass, oxygen consumption related to organics oxidation, and endogenous respiration with and without sludge recycle. Laboratory-scale experiments successfully showed high removal efficiencies for COD (94–95%), TOC (85–87%), and TSS (98–99%). The removal of organic matter was well described by a pseudo-first-order kinetic model, with rate constant (k) values of 0.055 and 0.059 L mg−1 VSS day−1, with and without biomass recirculation, respectively. The consumption of oxygen in the biological reactor was calculated according to parameters a′ (0.071/0.069 mg O2 mg−1 COD) and b′ (0.012/0.024 mg O2 mg−1 VSS day−1), experimentally obtained by operating the reactor with and without sludge recycle. The parameters related to the production and destruction of biomass were also determined: a = 0.33/0.32 mg VSS mg−1 COD; b = 0.07/0.03 mg VSS mg−1 VSS day−1, respectively, for the systems with and without sludge recycle.
The co-digestion of residues from the pre-treatment process of waste vegetable oil (OW) and pig manure (PM) was performed under different OW/PM feed ratios (1:0, 1:1 and 1:3 v/v) and at organic loading rates ranging from 0.25 to 3.1 kg VS m−3 day−1 in lab-scale single-phase (SP) and two-phase (TP) systems. From the experiments, it was observed that digestion of OW alone was inhibitory for the anaerobic degradation. Mixing OW with PM neutralized the negative effects of lipids accumulation and high VS removal efficiencies were realized in both systems (63 and 71 % in SP system and 69 and 72 % in TP system, at 1:1 and 1:3 OW/PM mixtures, respectively). Under the same operational conditions, the methane yield was 0.30 and 0.22 m3 CH4 kg−1 VS removed for the SP anaerobic digester and 0.30 and 0.27 m3 CH4 kg−1 VS removed for the TP configuration. Additionally, TP digestion presented more stable operation and higher treatment capacity.
Petroleum hydrocarbons in the bilge water of small fishing vessels are continuously released into the environment. The bilge water samples usually contained low amounts of oil-degrading bacteria; therefore, this study examines application of polyurethane foam (PUF)-immobilized Gordonia sp. JC11, a known lubricant-degrading bacterial inoculum, for the treatment of bilge water. Batch microcosm experiments showed that the PUF-immobilized bacteria were more efficient at removing oil than indigenous microorganisms and were able to remove approximately 40–50 % of the boat lubricant (1,000 mg L−1). The immobilized PUF samples rapidly adsorbed oil from the bilge water inside a small fishing vessel; however, the uninoculated PUF contained more oil than the inoculated PUF at most time points. The hydrocarbon components were also different when comparing inoculated and uninoculated PUF. These results indicate that the oil accumulated inside the PUF containing immobilized bacteria was being degraded by the Gordonia sp. JC11. However, these bacteria gradually die off after repeated oil exposure, and it is suggested that PUF-immobilized cells be replaced at timed intervals. This technique is considered simple and cheap; thus, it could be used to reduce chronic oil pollution from the release of bilge water.
Anaerobic ammonium-N removal from modified greenhouse turtle breeding wastewater with different chemical oxygen demand (COD) strengths (194.0-577.8mgL(-1)) at relatively fixed C/N ratios (∼2) was investigated using a lab-scale up-flow anaerobic sludge blanket (UASB) anammox reactor. During the entire experiment, the total nitrogen (TN) removal efficiency was about 85% or higher, while the average COD removal efficiency was around 56.5±7.9%. Based on the nitrogen and carbon balance, the nitrogen removal contribution was 79.6±4.2% for anammox, 12.7±3.0% for denitrification+denitritation and 7.7±4.9% for other mechanisms. Denaturing gradient gel electrophoresis (DGGE) analyses revealed that Planctomycete, Proteobacteria and Chloroflexi bacteria were coexisted in the reactor. Anammox was always dominant when the reactor was fed with different COD concentrations, which indicated the stability of the anammox process with the coexistence of the denitrification process in treating greenhouse turtle breeding wastewater.
To combine the advantage of the oleaginous yeast Yarrowia lipolytica with the high activity of some fungal lipases for oily wastewater treatment, an effective lipase-displaying arming yeast was constructed using the flocculation functional domain of Saccharomyces cerevisiae as the protein anchor. To estimate the effect of the whole-cell oily wastewater treatment, the lipase-displaying arming yeast was added into an open activated sludge bioreactor. Within 72h of whole-cell treatment, 96.9% of oil and 97.6% of chemical oxygen demand (COD) were removed, while only 87.1% of oil and 91.8% of COD were removed in control A (Y. lipolytica Polg was added), 45.1% of oil and 67.5% of COD were removed in control B (no cell was added) in 72h. The lipase-displaying arming yeast exhibited remarkable oil removal and COD degradation effect compared with the control samples, exemplifying its application potential.
A novel approach was developed to enhance the efficiency of the dissolved air flotation (DAF) for biodiesel wastewater by acidification and coagulation. Firstly, Grease & Oil and Chemical oxygen demand (COD) removal efficiencies of biodiesel wastewater using acidification with pure hydrochloric acid and pure sulfuric acid at pH=3 and 1day retention time were more than 80%, and 50%, respectively. Secondly, Grease & Oil and COD removal efficiencies of biodiesel wastewater using alum, polyaluminum chloride and ferric chloride coagulants without acidification at 1.0g/L were more than 90% and 30%. Thirdly, DAF alone and DAF with acidification could not separate Grease & Oil from biodiesel wastewater. Thus, DAF with the acidification and coagulation is suggested for biodiesel wastewater treatment. Biodiesel wastewater treatment by acidification before alum coagulation allowed the alum concentration to be reduced by 60–90% compared to treating without acidification. In addition, the efficiency of Grease & Oil removal from biodiesel wastewater by DAF with alum and acidification was 85–95%. It can be concluded that the efficiency of Grease & Oil removal from biodiesel wastewater using DAF with acidification and coagulation was 10% greater compared to other processes.
The Kinneil intertidal area, situated in the middle reaches of the Forth estuary, eastern Scotland, has been subject to the effects of industrial discharges, principally from petro-chemical industries (oil refinery and chemical works) since the 1920s.The intertidal fauna has been studied annually since 1976 using consistent methodology (90 stations, each with two samples of 5 × 5 × 5 cm, through a 250 μm sieve). The study continues, now providing over 20 yr of data.During the study period the discharges from the industrial sources have been reduced substantially through a combination of plant closure and modernization and the installation of effluent treatment works. Furthermore, the River Avon which flows across the area has experienced substantial improvements in water quality, attributed to improvements in waste treatment works at localities upstream from the estuarine site.Fluctuations of the faunal composition of the mudflats have been studied over the period. Some species, such as Hydrobia ulvae, Cerastoderma edule, and Nereis diversicolor show substantial fluctuations but no clear trend, whilst others such as Corophium volutator, Macoma balthica and Eteone longa show clear increases in abundance.Overall, however, the clearest trends have been increases in diversity, expressed either as mean number of species per station, or as diversity indices. These increases in diversity are shown to be a clear community response to the improvements made to the petro-chemical wastes discharged to the area.
High rate algal ponds (HRAPs) are an efficient treatment for controlling wastewater pollution by reducing the organic matter and the inorganic nutrient content. An experimental HRAP was set up in Mèze (France) and sampled over 24 months. A model simulating orthophosphate (PO4) evolution was constructed using Stella II software. It was thought that deterministic modelling of the temporal evolution of PO4 might provide a rational basis for pond management policies. In hardwater, two processes have to be taken into consideration: PO4 uptake by algae and PO4 precipitation. The model also has to take into account the fact that the latter process is very sensitive to nycthemeral variations in pH.Simulated PO4 concentrations over a two-year period show that about 10% of total input is removed by precipitation whereas about 30% is removed by absorption. These results are of critical importance for the management of this type of wastewater treatment system.
A novel rotating biological contactor (RBC) with biodrum was designed to remove hydrocarbons in wastewater from industrial discharges, and its performance was investigated. The biodrum, a cylindrical mesh drum, filled with random packing of polyurethane foam cubes retaining petroleum-degrading achlorophyllous micro-alga Prototheca zopfii cells, was approximately 40% submergence in the culture. The amount of algal cells, immobilized in the 10-mm-cube pieces, was greater than in pieces of smaller pore size under the experimental conditions studied. A mixture of n-alkanes (C14, C15 and C16) was used as a model oil, and the influent hydrocarbons were removed by immobilized cells in the biodrum. The single-stage RBC system was operated at 25°C and at pH 7.0 in a batch mode. The removal rate for n-alkanes in the RBC with biodrum system was significantly increased as compared to those in the RBC system with polycarbonate biodisk.
Chitosan is a partially deacetylated polymer obtained from the alkaline deacetylation of chitin, a biopolymer extracted from shellfish sources. Chitosan exhibits a variety of physico-chemical and biological properties resulting in numerous applications in fields such as cosmetics, biomedical engineering, pharmaceuticals, ophthalmology, biotechnology, agriculture, textiles, oenology, food processing and nutrition. This amino-biopolymer has also received a great deal of attention in the last decades in water treatment processes for the removal of particulate and dissolved contaminants. In particular, the development of chitosan-based materials as useful coagulants and flocculants is an expanding field in the area of water and wastewater treatment. Their coagulation and flocculation properties can be used to remove particulate inorganic or organic suspensions, and also dissolved organic substances. This paper gives an overview of the main results obtained in the treatment of various suspensions and solutions. The effects of the characteristics of the chitosan used and the conditions in solution on the coagulation/flocculation performance are also discussed.
This book presents the techniques, technologies, regulations, and strategies that define pollution prevention. The subject is addressed from many perspectives by prominent experts. In many ways pollution prevention, rather than being a specialty field itself, is actually a convergence of fields drawing upon knowledge in a wide variety of more typical fields of expertise. Individual chapters have been processed separately for inclusion in the appropriate data bases.
Pseudoxanthomonas sp. RN402 was capable of degrading diesel, crude oil, n-tetradecane and n-hexadecane. The RN402 cells were immobilized on the surface of high-density polyethylene plastic pellets at a maximum cell density of 10(8) most probable number (MPN) g(-1) of plastic pellets. The immobilized cells not only showed a higher efficacy of diesel oil removal than free cells but could also degrade higher concentrations of diesel oil. The rate of diesel oil removal by immobilized RN402 cells in liquid culture was 1,050 mg l(-1) day(-1). Moreover, the immobilized cells could maintain high efficacy and viability throughout 70 cycles of bioremedial treatment of diesel-contaminated water. The stability of diesel oil degradation in the immobilized cells resulted from the ability of living RN402 cells to attach to material surfaces by biofilm formation, as was shown by CLSM imaging. These characteristics of the immobilized RN402 cells, including high degradative efficacy, stability and flotation, make them suitable for the purpose of continuous wastewater bioremediation.
This research investigated the application of Bio-Amp, a commercial bio-additive for the treatment of fat, oil, and grease (FOG) in a grease trap, and evaluated potential impacts of treated effluent on downstream collection system and treatment processes. Results show that after Bio-Amp treatment, FOG deposit formation was reduced by 40%, implicating a potential reduction of sewer line blockages. Chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and total fatty acids were reduced by 39%, 33%, 56%, and 59%, respectively, which represents an overall loading reduction of 9% COD, 5% TN and 40% TP received by the treatment plant from all the dining halls. On the other hand, readily biodegradable COD fractions significantly increased, which implies a potential improvement on Bio-P removal. Overall, the results showed that application of Bio-Amp in grease trap provides potential reduction of sewer line blockages, and can also alleviate downstream treatment burden.
An agricultural waste, barley straw, was chemically modified using a cationic surfactant hexadecylpyridinium chloride monohydrate (CPC) to obtain a biosorbent for removal of emulsified mineral oil from aqueous solution. The physical and chemical properties of the raw and surfactant-modified barley straw (SMBS) were characterized by N2 adsorption, bulk density, Fourier transforms infrared spectra and the composition of cellulose, hemicellulose and lignin. The adsorption tests were performed using a standard mineral oily wastewater in a batch adsorption system. The effects of contact time and pH of solution on the emulsified oil uptake were investigated and discussed. It was found that the removal efficiency of emulsified oil increased with the increase in contact time. Biosorption was found to be less favorable at high acidic condition and a maximum removal was obtained at about neutrality. The isotherm study indicated that emulsified oil adsorption on SMBS was fitted well with the Langmuir model rather than the Freundlich model. The maximum adsorption capacity determined from the Langmuir isotherm was 518.6 mg g−1 at 25 °C. The kinetic study revealed that equilibrium time was achieved in less than 40 min and the kinetic data were fitted well to the pseudo-first-order model. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
The slightly polluted wastewater from oil refinery contains some COD, oil pollutants and suspended solids (SS). A small-scale
fixed film biological aerated filter (BAF) process was used to treat the wastewater. The influences of hydraulic retention
time (HRT), air/water volume flow ratio and backwashing cycle on treatment efficiencies were investigated. The wastewater
was treated by the BAF process under optimal conditions: the HRT of 1.0 h, the air/water volume flow ratio of about 5:1 and
the backwashing cycle of every 4–7 days. The results showed that the average removal efficiency of COD, oil pollutants and
SS was 84.5%, 94.0% and 83.4%, respectively. And the average effluent concentration of COD, oil pollutants and SS was 12.5,
0.27, 14.5 mg·L−1, respectively. The experimental results demonstrated that the BAF process is a suitable and highly efficient method to treat
the wastewater.
The aim of this research is inspecting the efficiency of physical-chemical and biological processes with the active sludge
method in the wastewater of the Pars Oil Refinery Company. This research was done from 26th, January 2007 and continued up
to 27th, May 2007. The main operation in Pars oil refinery is to produce lubricants. This research tries to examine and evaluate
the performance of treatment system at the refinery to decrease microorganism in the industrial wastewater in a laboratory
scale pilot. The pilot has two sections; physical-chemical section, including Dissolved Air Flotation system, and biological
section, including active sludge reactor and clarifier. This investigation carried on a 10 liter Dissolved Air Flotation reactor
and an active sludge reactor in a laboratory scale. The volume of the aerireactor (aeration reactor) was 10 liters, and the
volume of the secondary sediment was 3.5 liters. The waste water of the refinery was used as inlet flow of the pilot and necessary
sludge was obtained at first from the Shahrak Ekbatan waste water treatment system. After analyzing the test results, it was
concluded that the average percentage of excluding oil, Chemical Oxygen Demand and Biological Oxygen Demand was 29.7, 49 and
27.8 respectively. This indicates the effective role of physical treatment in decreasing oily emulsion material that would
result in decreasing organic density in untreated wastewater. In biological system, the efficiency of excluding Chemical Oxygen
Demand and Biological Oxygen Demand is 73.4 and 84.7, respectively. This confirms high efficiency of this unit. The samples
taken from entering (influent) and exiting (effluent) wastewater of both units were tested. Standard Methods were applied
to determine the considered physical and chemical parameters.
Keywordsactivated sludge–aerireactor–dissolved air flotation–oil refinery
In this study, waste water of Kιrιkkale Refinery (Turkey) was treated with coagulants (alum, ferric chloride, ferrous sulfate and lime) and coagulant aids (polyelectrolytes: anionic, cationic, nonionic) and some Turkish clays namely Samaş, Çanbensan, Ceylan, Hasandede and Keskin in order to see their effects in clarifying the waste water before biopurification. The results showed that local clays (Hasandede and Keskin) are as efficient as bentonites (Samaş, Çanbensan and Ceylan). The clarifying efficiency of clays in combination with coagulants shows almost the same results of about 90%. The effect of coagulants, FeCl3, FeSO4 and CaO, was similar to that obtained with Al2(SO4)3. The efficiency of polymeric materials especially cationic and anionic polymers was found to be better than that obtained with clays.
As an alternative to the conventional activated sludge (CAS) process, this paper investigates the use of B350M and B350 group microorganisms immobilized on carriers in a pair of Biological Aerated Filter (BAF) reactors to pre-treat oil field wastewater before desalination. By operating the biodegradation system for 142 days with a hydraulic retention time (HRT) of 4 h and volumetric load 1.07 kg COD (m3 d)−1 at last, the reactor immobilized with B350M achieved mean degradation efficiencies of 78% for total organic carbon (TOC) and 94% for oil, whereas that with B350 only reached 64% for TOC and 86% for oil. The influent wastewater contains organic substances from C13H28 to C32H66, and a total of 16 polycyclic aromatic hydrocarbons (PAHs). The degradation efficiencies of PAHs in the BAF immobilized with B350M and B350 microorganisms are 90% and 84%, respectively. It is observed that the biological diversity of microorganisms in the reactor containing B350M (seven more strains of bacteria survive) is richer than in that containing B350. A large quantity of filamentous microorganisms developed in both reactors without causing foaming or bulking.
Species of Suillus produce fleshy, pored mushrooms. They are important symbiotic (ectomycorrhizal) partners of many coniferous trees. The genus includes several putative eastern Asian and eastern North American disjunct species, i.e., the S. americanus–S. sibiricus and S. decipiens–S. spraguei complexes. Phylogenetic relationships among the groups were determined to further understand the biogeographic pattern. Analyses were based on 40 sequences of the ITS region of the nuclear ribosomal RNA tandem repeats, representing 18 distinct species/populations. Our phylogenetic analyses suggested that: (1) Chinese and United States' (U.S.) S. spraguei plus S. decipiens form a strongly supported monophyletic group, with North American S. decipiens and Chinese S. spraguei being sister taxa; (2) S. americanus, Asian and U.S. S. sibiricus, plus S. umbonatus form a clade supported by a high bootstrap value; and (3) little ITS sequence divergence exists within the latter group compared to the S. decipiens–S. spraguei clade. Phylogenetic patterns revealed by this study imply a close phylogenetic relationship between eastern Asian and eastern North American disjunct population/species of Suillus. These fungi display relatively high host fidelity (at least to the host subgenus level), suggesting potential coevolutionary/comigratory trends.
This paper presents a review of the procedures to design and retrofit water networks. Although the emphasis is in showing results for refineries, the methods are valid for any process plants. It is first shown that the problem has been decomposed into the design of two interacting subsystems. One problem is the freshwater and wastewater reuse allocation and the other is the wastewater treatment problem. It is also shown how the wastewater treatment problem was modeled as a distributed and decentralized treatment. The roadmap towards zero liquid discharge and energy integrated solutions is then discussed. Several solution approaches are briefly outlined emphasizing the main trend leaning towards the use of mathematical programming. The major claim made is that mathematical programming can produce globally optimal solutions and practically important sub-optimal solutions when conceptual insights are employed to build the models. Although the paper intends to be comprehensive, it emphasizes the author's recent work. Finally, a few of the existing challenges of the area are outlined.
Phosphorus removal by the activated algae process was studied in laboratory scale under various conditions of hydraulic loading. Phosphorus removal ranged from 70% at 4 h hydraulic retention time, to 95% at 12 h hydraulic retention time. Chemical precipitation was found to be the predominant mechanism for phosphorus removal. An optical device for introducing light to the process was used which, based on theoretical consideration, significantly increases the efficiency of light utilization by algae cultures.
Pollution of the aquatic environment occurs from many different sources including from oil refineries. Oil refinery effluents contain many different chemicals at different concentrations including ammonia, sulphides, phenol and hydrocarbons. The exact composition cannot however be generalised as it depends on the refinery and which units are in operation at any specific time. It is therefore difficult to predict what effects the effluent may have on the environment. Toxicity tests have shown that most refinery effluents are toxic but to varying extents. Some species are more sensitive and the toxicity may vary throughout the life cycle. Sublethal tests have found that not only can the effluents be lethal but also they can often have sublethal effects on growth and reproduction. Field studies have shown that oil refinery effluents often have an impact on the fauna, which is usually restricted to the area close to the outfall. The extent of the effect is dependent on the effluent composition, the outfall's position and the state of the recipient environment. It is possible to detect two effects that oil refinery effluent has on the environment. Firstly it has a toxic effect close to the outfall, which is seen by the absence of all or most species. Secondly there is an enrichment effect which can be distinguished as a peak in the abundance or biomass. These effects are not limited to just oil refinery effluents, which makes it difficult to distinguish the effects an oil refinery effluent has from other pollution sources. The discharge from oil refineries has reduced in quantity and toxicity over recent decades, allowing many impacted environments in estuaries and coasts to make a substantial recovery.
This article sets out to survey the remarkable development that has taken place in catalysis in the refining and petrochemical industries since the middle of the 20th century, and more especially since the 1970s, highlighting what appears to be the most significant progress. It then attempts to outline the energy and environmental context for the coming decades which will govern the trend in industrial catalysis in the 21st century. Although the reduction of CO2 will eventually require the decarbonization of energy carriers, oil will still remain the principal source of liquid motor fuels for a long time. However, the share of gas will gradually increase and hydrogen is destined to play an important part as an energy carrier. The use of biomass will develop, but at a modest level. Within this framework, catalysis will still play a leading role in technical and economic development in the 21st century, even though it is far from being an emerging discipline.
Aerobic degradation of a crude oil (sample P1), collected from a deep water reservoir from the Pampo Sul Field (Campos Basin, RJ) at 82 °C and 2405–2588 m, by indigenous bacteria in the oil and formation water was monitored for 60 days. Degradation parameters, measured using gas chromatography–mass spectrometry (GC–MS) of the crude oil degraded in the laboratory for periods of 0, 30, 50 and 60 days, were compared with those of a naturally biodegraded oil (sample P2). The analyses revealed that the n-alkanes were totally depleted by the 60th day when the crude oil (P1, degradation level 2) was transformed into petroleum of biodegradation level 6 (P2).
The expression “best available techniques” is defined in Section 5 of the U.S. Environmental Protection Agency Acts, 1992 and 2003, and Section 5(2) of the Waste Management Acts, 1996 to 2005, as the “most effective and advanced stage in the development of an activity and its methods of operation, which indicate the practical suitability of particular techniques for providing, in principle, the basis for emission limit values designed to prevent or eliminate or, where that is not practicable, generally to reduce an emission and its impact on the environment as a whole, where best in relation to techniques means the most effective in achieving a high general level of protection of the environment as a whole, available techniques means those techniques developed on a scale which allows implementation in the relevant class of activity under economically the technically viable conditions, taking into consideration the costs and advantages, whether or not the techniques are used or produced within the State, as long as they are reasonably accessible to the person carrying out the activity, and techniques includes both the technology used and the way in which the installation is designed, built, managed, maintained, operated and decommissioned” (EPA, 2008).
An internal loop airlift bioreactor containing chitosan-immobilized Sphingobium sp. P2 was applied for the removal of automotive lubricants from emulsified wastewater. The chitosan-immobilized bacteria had higher lubricant removal efficiency than free and killed-immobilized cells because they were able to sorp and degrade the lubricants simultaneously. In a semi-continuous batch experiment, the immobilized bacteria were able to remove 80-90% of the 200 mg L(-1) total petroleum hydrocarbons (TPH) from both synthetic and carwash wastewater. The internal loop airlift bioreactor, containing 4 g L(-1) immobilized bacteria, was later designed and operated at 2.0 h HRT (hydraulic retention time) for over 70 days. At a steady state, the reactor continuously removed 85±5% TPH and 73±11% chemical oxygen demand (COD) from the carwash wastewater with 25-200 mg L(-1) amended lubricant. The internal loop airlift reactor's simple operation and high stability demonstrate its high potential for use in treating lubricants in emulsified wastewater from carwashes and other industries.
An upflow anaerobic sludge blanket (UASB) bioreactor was successfully used for the treatment of petroleum refinery effluent. Before optimization, chemical oxygen demand (COD) removal was 81% at a constant organic loading rate (OLR) of 0.4 kg/m(3) d and a hydraulic retention time (HRT) of 48 h. The rate of biogas production was 559 mL/h at an HRT of 40 h and an influent COD of 1000 mg/L. Response surface methodology (RSM) was applied to predict the behaviors of influent COD, upflow velocity (V(up)) and HRT in the bioreactor. RSM showed that the best models for COD removal and biogas production rate were the reduced quadratic and cubic models, respectively. The optimum region, identified based on two critical responses, was an influent COD of 630 mg/L, a V(up) of 0.27 m/h, and an HRT of 21.4 h. This resulted in a 76.3% COD removal efficiency and a 0.25 L biogas/L feed d biogas production rate.
A circulating photocatalytic reactor was used for removing aliphatic and aromatic organic pollutants in refinery wastewater. The TiO(2) added wastewater samples, while saturating with air, were irradiated with an immersed mercury UV lamp (400 W, 200-550 nm). Optimal catalyst concentration, fluid pH and temperature were obtained at amounts of near 100 mgL(-1), 3 and 318K, respectively. A maximum reduction in chemical oxygen demand of more than 90% was achieved after about 4h irradiation and hence, 73% after about only 90 min; significant pollutant removal was also achievable in the other conditions. The identification of the organic pollutants, provided by means of a GC/MS and a GC analysis systems, equipped with headspace injection technique, showed that the major compounds were different fractions of petroleum aliphatic hydrocarbons (up to C(10)) and the well-known aromatic compounds such as benzene, toluene and ethylbenzene. The results showed a high efficiency degradation of all of these pollutants.
Spirulina platensis was cultivated in a bench-scale airlift photobioreactor using synthetic wastewater (total nitrogen 412 mg L(-1), total phosphorous 90 mg L(-1), pH 9-10) with varying ammonia/total nitrogen ratios (50-100% ammonia with balance nitrate) and hydraulic residence times (15-25 d). High average biomass density (3500-3800 mg L(-1)) and productivity (5.1 g m(-2) d(-1)) were achieved when ammonia was maintained at 50% of the total nitrogen. Both high ammonia concentrations and mutual self-shading, which resulted from the high biomass density in the airlift reactor, were found to partially inhibit the growth of S. platensis. The performance of the airlift bioreactor used in this study compared favorably with other published studies. The system has good potential for treatment of high strength wastewater combined with production of algae for biofuels or other products, such as human and animal food, food supplements or pharmaceuticals.
Although highly diverse and specialized prokaryotic and eukaryotic microbial communities in soil degrade polycyclic aromatic hydrocarbons (PAHs), most of these are removed slowly. This review will discuss the biotechnological possibilities to increase the microbial dissipation of PAHs from soil as well as the main biological and biotechnological challenges.
Microorganism provides effective and economically feasible solutions for soil cleanup and restoration. However, when the PAHs contamination is greater than the microbial ability to dissipate them, then applying genetically modified microorganisms might help to remove the contaminant. Nevertheless, it is necessary to have a more holistic review of the different individual reactions that are simultaneously taking place in a microbial cell and of the interactions microorganism-microorganism, microorganism-plant, microorganism-soil, and microorganisms-PAHs.
Elucidating the function of genes from the PAHs-polluted soil and the study in pure cultures of isolated PAHs-degrading organisms as well as the generation of microorganisms in the laboratory that will accelerate the dissipation of PAHs and their safe application in situ have not been studied extensively. There is a latent environmental risk when genetically engineered microorganisms are used to remedy PAHs-contaminated soil.