Pretreatment of alkali/surfactant/polymer (ASP)-flooding produced wastewater by electron beam radiation to improve oil-water separation

The management of wastewater produced from alkali/surfactant/polymer (ASP) flooding, known for its considerable volume and high emulsion stability, poses a challenge in oilfields globally. This study has demonstrated that ionizing irradiation is a promising pretreatment method for ASP wastewater to improve oil-water separation. After a settling time of 1 h, approximately 69.5% of oil remained in the raw ASP wastewater, while only 20-29% of the oil persisted in the liquid phase following radiation at absorbed doses ranging from 0.1 to 5.0 kGy. A noticeable increase in the size of oil droplets and reduction in turbidity was observed after irradiation. Further analysis revealed that the combination of surfactant, sodium dodecyl sulfate (SDS) and alkali exhibits a synergistic impact, leading to a substantial reduction in interface tension of ASP wastewater. Notably, ionizing irradiation induces several key changes that are crucial for efficient demulsification. The transformation of the wastewater's rheological behavior from pseudoplastics to a Newtonian fluid accompanied by a reduction in viscosity, the increased interfacial tension at both liquid-air and liquid-oil interfaces, along with the degradation of organic components such as partly hydrolyzed polyacrylamide (HPAM) and SDS, all contribute to the coalescence and floatation of oil droplets.

Oilfield-produced water as a medium for the growth of Chlorella pyrenoidosa outdoor in an arid region

Oilfield-produced wastewater (OPW) provided by the local oil industry was used as a medium (without any pre-treatment) for the outdoor cultivation of microalgae Chlorella pyrenoidosa. The effectiveness of algal growth on the produced water treatment has been investigated. The experimental setups were carried out outdoor, under sunlight radiation, using an open system sited in the desert area. The highest biomass concentration was attaining 1.15 ± 0.07 g/L after 21 culture days. FTIR spectroscopy was used to estimate the lipid content in C. pyrenoidosa grown in BG11 and OPW medium. Daytime temperatures fluctuation was between 26 and 31 °C. The average insolation was no less than 10 h per day with maximum solar irradiation of 1036 ± 30 W/m², measured between 12 and 1 p.m. C. pyrenoidosa was found highly capable of removing COD, NH4 + -N, TN, and TP by 89.67%, 100%, 57.14%, and 75.51%, respectively, throughout the cultivation period. Biosorption of toxic heavy metal pollutants such as Cu, Pb, and Cd was also achieved at rates of approximately 73.39, 72.80, and 48.42%. Overall, the achieved result of C. pyrenoidosa-based process was compared to the actual process using activated carbon.

A critical review of environmental and public health impacts from the activities of evaporation ponds

Evaporation ponds (EVPs) are among the most cost-effective, and simple wastewater treatment technologies used in many regions/countries with high solar radiation levels. However, its operational limitations, which include the overflow of wastewater, leakages via liners, and large surface area of the EVP that is exposed to atmosphere, creates a negative feedback to the environment. Therefore, the main aim of this review study of more than a hundred works published a little all over the continents is to provide a summary of various contaminations that are associated with EVPs activities through different environmental compartments. In addition, the impacts of EVP on fauna, human health including the current on-site sustainable mitigation strategies were also reviewed. The first conclusion from this study shows that the most commonly contaminants released into surface waters, groundwater, soil and sediments were heavy metals, pesticides, herbicides, selenium, including several major anions and cations. Non-methane hydrocarbons (NMHCs), volatile organic compounds (VOCs), and particulate matters (PMs) were the main air pollutants emitted from the surfaces of an EVP. Limited data is available about the emissions of atmospheric greenhouse gas (GHGs) especially carbon dioxide (CO₂) and methane (CH₄) from EVP surfaces. Migratory birds and aquatic organisms are the most vulnerable fauna as EVP wastewaters can cause obstruction of movements, affect diversity, and causes mortalities following the exposure to the toxic wastewater. The study revealed limited data about the potential health risk associated with occupational and environmental exposure to radiological hazards and contaminated drinking water from EVP activities. On-site EVP treatment strategies using bioremediation and electrochemical treatment technologies have shown to be a promising sustainable mitigation approach. Knowledge gaps in areas of GHGs monitoring/modeling, pollution exposure estimation and health risk assessments are urgently required to gain deeper understanding about the impact of EVP activities, and incorporate them into future EVP designs.

Rapid removal of polyacrylamide from wastewater by plasma in the gas-liquid interface

Due to the severe restrictions imposed by legislative frameworks, the removal of polyacrylamide (PAM) rapidly and effectively from produced wastewater in offshore oilfields before discharge is becoming an urgent challenge. In this study, a novel advanced oxidation process based on plasma operated in the gas-liquid interface was used to rapidly decompose PAM, and multiple methods including viscometry, flow field-flow fractionation multi-angle light scattering, UV-visible spectroscopy, and attenuated total reflectance-Fourier transform infrared spectroscopy were used to characterize the changes of PAM. Under a discharge voltage of 25 kV and pH 7.0, the PAM concentration decreased from 100 to 0 mg/L within 20 min and the total organic carbon (TOC) decreased from 49.57 to 1.23 mg/L within 240 min, following zero-order reaction kinetics. Even in the presence of background TOC as high as 152.2 mg/L, complete removal of PAM (100 mg/L) was also achieved within 30 min. The biodegradability of PAM improved following plasma treatment for 120 min. Active species (such as O₃ and H₂O₂) were produced in the plasma. Hydroxyl radical was demonstrated to play an important role in the degradation of PAM due to the inhibitory effect observed after the addition of an ·OH scavenger, Na₂CO₃. Meanwhile, the release of ammonia and nitrate nitrogen confirmed the cleavage of the acylamino group. The results of this study demonstrated that plasma, with its high efficiency and chemical-free features, is a promising technology for the rapid removal of PAM.

Efficiencies and mechanisms of chemical cleaning agents for nanofiltration membranes used in produced wastewater desalination

A spiral-wound nanofiltration (NF) membrane module harvested from a full-scale produced wastewater desalination plant was examined and cleaned to explore appropriate chemical cleaning protocols. Foulant identification and cleaning efficiency and mechanisms were investigated. For total foulants, the organic components, including anionic polyacrylamide (APAM) and crude oil, accounted for a weight percentage of 86.3%, while the remaining foulants constituted the inorganic fraction, including Na, Mg, Ca, Ba, Al, Fe and Si. Short-term cleaning experiments were designed to identify effective reagents that could be used for further evaluations of their cleaning efficiencies in long-term cleaning. For citric acid and ethylenediaminetetraacetic acid tetrasodium (EDTA-4Na), the long-term cleaning efficiencies were relatively slight or even negative, while said values varied with different surfactants. Dodecyltrimethylammonium chloride (DTAC) achieved the greatest flux recovery; conversely, cetyltrimethylammonium chloride (CTAC) provided insignificant, even negative effects, on flux recovery, as well as salt rejection, of the fouled NF membranes. FTIR and zeta potential analyses of the fouled membranes indicated that all the tested surfactants were identically effective in removing the foulants from the membrane surface, but their cleaning efficiencies differed. Moreover, a strong correlation between the flux ratio (S_f) and concentration of surfactant in the permeate (C_ps) was observed. Among the tested chemical reagents, DTAC yielded the highest C_ps and the greatest flux recovery, with an S_f of 2.25. Considering this correlation and the characteristics of the fouled membranes and surfactants, it is proposed that DTAC molecules penetrated the membrane pores and removed the foulants that were attached to the pore walls.