Hybrid biological, electron beam and zero-valent nano iron treatment of recalcitrant metalworking fluids

The Green Method in Water Management: Electron Beam Treatment

During the prebiotic era, radiolytic transformations in the oceans played a key role in purifying water from toxic impurities and, thus, played a role in the formation of the aquatic environment of our planet, making it suitable for the emergence of life. Today, the planet again faces the challenge of how to provide people with clean water. Therefore, it is reasonable to look back at past historical stages and again consider the possibility of neutralizing pollutants in water by means of radiolysis, which has already been tested by time. Modern radiolytic treatments can be much faster and safer thanks to the advent of powerful electron accelerators and high-rate electron beam treatment (ELT) of water and wastewater. Radiolytic treatment of water using accelerated electrons corresponds to the essence of advanced oxidative technologies and green chemistry. The ELT of water instantly generates a high concentration of short-lived radicals that can quickly neutralize and decompose chemical and bacterial pollutants. Due to the ability of accelerated electrons to penetrate into a substance, ELT provides the decomposition of both dissolved and suspended pollutants. The cleaning effect of ELT is due to the ability to inactivate toxic and chromophore functional groups, transform impurities into an easily removable form, damage the DNA of microorganisms and their spore forms, and increase the biodegradability of organic impurities. The use of ELT in water treatment provides significant savings in chemical reagents, thereby improving quality and reducing the number of cleaning steps. The compactness, high degree of automation of the equipment used, energy efficiency, high productivity, and excellent compatibility with traditional water treatment methods are important advantages of ELT. Unlike conventional chemicals, the excess radicals generated in the ELT process are converted back to water and hydrogen; thus, the chemical and corrosive activity of water does not increase. Equipping research institutes with electron accelerators, developing cheaper accelerators, and granting government support for pilot projects are key conditions for introducing ELT into water treatment practice.

In situ treatment of metalworking wastewater by chemical addition-dissolved air flotation coupled with UV, H2O2 & ZnO

The hybrid treatment techniques have been proven that could be a proper solution to the metalworking fluid (MWF) wastewaters disposal challenge. Hence, this investigation was conducted aim to the assessment of chemical addition-dissolved air floatation (CA-DAF) unit followed with a heterogeneous photocatalytic (PC) process as UV/H₂O₂/ZnO to treat MWF wastewater produced in one of the central industrial estates in the Middle East. The CA-DAF unit was implemented as trial and errors and had an appropriate efficiency. However, the environmental discharge standards were not achieved only by this unit, so that, a PC process considered for this purpose in a pilot-scale reactor. And also, Chemical oxygen demand (COD), total petroleum hydrocarbons (TPHs) were considered as physicochemical parameters to analyze the applied photochemical reaction throughout the concentrations of ZnO and H₂O₂, and pH value as variables of the study. The ideal and optimized conditions were observed at pH 10, 600 mg l^-1 of ZnO, and 13.11 g l^-1 of H₂O₂ via 99.87% and 97.9% reduction rates in total COD and TPH, respectively. These removal rates were obtained for this integrated strategy under the optimized reaction. By evaluating the synergistic effect, it was found that UV/ZnO could be a predominant reaction in this process. The organic and intermediates analysis appeared 78.46% reduction for all detected organic matters. Besides, PC generation of bis phthalate, mono phthalate, benzene, and benzoic acid to 2,6-bis (1,1-dimethylethyl)-4-mthyl phenol was the reason of the residual phenolic compound concentration in the reaction solution with low removal rate. The kinetic study showed that this reaction could be well fitted with the pseudo-first-order kinetic model by R ² equal with 0.973 and 0.988 in turn for COD and TPH. The expenditures to treat 1 m³ of the CA-DAF was estimated at 5.335 us$ via cost analysis. Finally, the collected findings indicate that CA-DAF integrated with UV/H₂O₂/ZnO can be an efficient approach in the MWF wastes disposal or treatment for reuse.

Selection and assembly of indigenous bacteria and methanogens from spent metalworking fluids and their potential as a starting culture in a fluidized bed reactor

Waste metalworking fluids (MWFs) are highly biocidal resulting in real difficulties in the, otherwise favoured, bioremediation of these high chemical oxygen deman (COD) wastes anaerobically in bioreactors. We have shown, as a proof of concept, that it is possible to establish an anaerobic starter culture using strains isolated from spent MWFs which are capable of reducing COD or, most significantly, methanogenesis in this biocidal waste stream. Bacterial strains (n = 99) and archaeal methanogens (n = 28) were isolated from spent MWFs. The most common bacterial strains were Clostridium species (n = 45). All methanogens were identified as Methanosarcina mazei. Using a random partitions design (RPD) mesocosm experiment, we found that bacterial diversity and species-species interactions had significant effects on COD reduction but that bacterial composition did not. The RPD study showed similar effects on methanogenesis, except that composition was also significant. We identified bacterial species with positive and negative effects on methane production. A consortium of 16 bacterial species and three methanogens was used to initiate a fluidized bed bioreactor (FBR), in batch mode. COD reduction and methane production were variable, and the reactor was oscillated between continuous and batch feeds. In both microcosm and FBR experiments, periodic inconsistencies in bacterial reduction in fermentative products to formic and acetic acids were identified as a key issue.

Comparison of metalworking fluids biodegradation efficiency by autochthonous and environmental communities

The aim of this study was to evaluate the biodegradation potential of microbiota isolated from different environmental niches towards different types of metalworking fluids (MWF). The first experimental stage was focused on the assessment of biochemical oxygen demand reduction efficiency of autochthonous and environmental microbial communities. Based on the obtained results, the following order describing the biodegradation potential of communities from the studied niches was established: petroleum contaminated soil > waste repository ≥ waste MWF tanks > pesticide-treated field > activated sludge > municipal sewage effluents. For comparative purposes, the most efficient community originating from petroleum contaminated soil (PCS1) was selected for further studies along with the most efficient community originating from a waste MWF tank (WMT1). The studied communities achieved 100% biodegradation efficiency of decanedioic and dodecanedioic acids as well as glycerine and polyethoxylated dodecanol. However, the PCS1 community was more versatile and displayed significantly higher biodegradation efficiency of mineral oil (80% compared to 50% in case of WMT1). Similarly, experiments using pristine and spent MWF solutions confirmed that the PCS1 community outperformed the WMT1 community during the biodegradation of MWF containing oil as the main component (COD reduction of 80, 60 and 30% in case of semi-synthetic MWF, soluble oil and spent MWF, respectively). Results of community dynamics assessment using quantitative real-time PCR after the biodegradation of different types of MWF confirmed that the PCS1 community was characterized by high genetic stability and allowed to indicate the potential 'key players'.

Influences of ammonium and phosphate stimulation on metalworking fluid biofilm reactor development and performance

In this study, the effects of common wastewater stimulants, namely NH₄Cl and KH₂PO₄, on the development and performance of metalworking fluid biofilm bioreactors are presented. It is shown that biofilms flourished only when one of these components was present in limiting quantities. Biofilm yields significantly declined when both of the components were withheld from the bioreactors or when both components were provided in excess. Stimulations to the reactors using NH₄Cl significantly reduced the total carbon removal performance, while stimulations using KH₂PO₄ resulted in significant increases in performance. Chromatographic analyses showed that the NH₄Cl stimulation enhanced the removal of saturated fatty amides and diethylene glycol butyl ether from the metalworking fluid, but inhibited the removal of diisoproponolamine. Furthermore, NH₄Cl additions inhibited the oil/water separation carbon removal mechanism and resulted in the re-dispersion of recalcitrant organic material. The results from this study show that metalworking fluid practitioners should take care in choosing the nutrients used for stimulating bioreactor performance and microbe development. Incorrect stimulations with NH₄Cl may result in negative treatment performances due to the inhibition of amine utilisation and enhancing emulsion stability.

Can radiation chemistry supply a highly efficient AO(R)P process for organics removal from drinking and waste water? A review

The increasing role of chemistry in industrial production and its direct and indirect impacts in everyday life create the need for continuous search and efficiency improvement of new methods for decomposition/removal of different classes of waterborne anthropogenic pollutants. This review paper addresses a highly promising class of water treatment solutions, aimed at tackling the pressing problem of emerging contaminants in natural and drinking waters and wastewater discharges. Radiation processing, a technology originating from radiation chemistry studies, has shown encouraging results in the treatment of (mainly) organic water pollution. Radiation ("high energy") processing is an additive-free technology using short-lived reactive species formed by the radiolysis of water, both oxidative and reducing, to carry out decomposition of organic pollutants. The paper illustrates the basic principles of radiolytic treatment of organic pollutants in water and wastewaters and specifically of one of its most practical implementations (electron beam processing). Application examples, highlighting the technology's strong points and operational conditions are described, and a discussion on the possible future of this technology follows.

Phosphorus Depletion as a Green Alternative to Biocides for Controlling Biodegradation of Metalworking Fluids

Metalworking fluids (MWFs) are used as lubricants and coolants in the manufacturing operations. Their biodeterioration, while in operation, is a widespread problem leading to poor performance and worker health issues. Adding biocides, though effective in reducing microbial growth, leads to the production of more recalcitrant wastewaters that are difficult to dispose or recycle on-site. Increasing environmental concerns have led to robust legislation for reducing/eliminating the use of toxic biocides in MWFs, stimulating a growing interest in the development/application of alternative biological preservation strategies. In this study, inducing nutrient imbalance was investigated for controlling microbial growth in MWFs. Phosphorus was immobilized employing insoluble La₂O₃ to form LaPO₄. Concentrations of La₂O₃ greater than 0.08%w (%w = weight percent) completely inhibited microbial growth (from 1.4 × 10⁷ to 0 CFU/mL) and hindered biodegradation. Raman spectroscopy suggested that La₂O₃ converted intracellular phosphorus into LaPO₄. The growth inhibition potentials of both 0.06%w La(NO₃)₃ and La₂O₃ were found to be superior to formaldehyde. The antimicrobial property of La₂O₃ (i.e., inhibition) was tenable by adding sufficient phosphate, acting as an on/off switch for controlling microbial growth in MWFs. This technology offers the potential to reduce/eliminate the use of biocides in MWFs, improves the feasibility of end-of-life biological treatment, and closes the water loop.