Oil refinery hazardous effluents minimization by membrane filtration: An on-site pilot plant study

A novel physical-biochemical treatment of refinery wastewater

As of 2022, China has achieved a crude oil processing capacity of 918 million tons, leading to a notable escalation in the production of refinery wastewater. The composition of refinery wastewater is intricate and diverse, posing a substantial challenge to its treatment. In order to facilitate appropriate discharge or reuse, an exhaustive separation process is imperative for refinery wastewater. Conventional pre-treatment processes typically employ inclined plate separators and dissolved air flotation (DAF) for the removal of oil and suspended solids (SS), while sequencing batch reactor (SBR), oxidation ditch, or biological aerated filter (BAF) are employed for the biological treatment process. However, these approaches encounter challenges such as a large spatial footprint, suboptimal treatment efficiency, and high energy consumption. In response to these challenges, this study introduces a novel integrated apparatus consisting of a high-efficiency oil remover (HEOR), coalescence oil remover (COR), and an airlift-enhanced loop bioreactor (AELR). A pilot-scale test was conducted to evaluate the performance of this integrated system in practical field applications. The pilot-scale tests reveal that, without the addition of chemical agents, the petroleum removal efficiency of "HEOR + COR" system was 1.2 times that of DAF. Compared with the SBR system, AELR's volume loading was increased by 1.56 times. The effluent quality achieved in the pilot-scale tests attained parity with that the original process. The "HEOR + COR + AELR" system exhibited energy and carbon emissions reduction of 28% and 30% compared to the "DAF + SBR" system, respectively. Therefore, the operating costs was reduced by approximate 1 Chinese Yuan (CNY) per ton of treated water. This technological advancement serves as a valuable reference for the implementation of low-carbon treatment of refinery wastewater.

A Superstructure Based Optimization Approach for Regeneration Reuse of Water Network: Optimal Design of a Detailed Nanofiltration Regenerator Network

Increasing freshwater costs and environmental concerns have necessitated the adoption of strategies for reducing freshwater consumption and effluent water discharge in chemical processes. Regeneration technologies increase opportunities for water reuse and recycle, and nanofiltration has emerged as a competitive wastewater regeneration technology. However, the optimal design of nanofiltration networks has not been extensively investigated. This study presents a framework for the optimal design and synthesis of multicontaminant nanofiltration membrane regenerator networks for application in water minimization problems. Mathematical optimization technique is developed based on a superstructure containing all system components and streams, incorporating nanofiltration units, pumps, and energy recovery devices. A linear approach and the modified Spiegler-Kedem model are explored in modelling the nanofiltration, and the steric-hindrance pore model is used to characterize the membrane. The objective of the optimization is to simultaneously minimize the water consumption and the total annual cost of the network. Furthermore, the optimal size, configuration, membrane properties and operating conditions of the equipment are determined. The applicability of the model is illustrated using a case study of an integrated pulp and paper plant. It was found that detailed models with customized modules are more useful when compared to the linear “black box” approach and approaches using fixed module specifications. The customized, detailed design of the regenerator network increased freshwater savings by 24% when compared to a black-box model, 31% when compared to a detailed model with fixed module specifications and 41% when compared to a reuse-recycle system with no regeneration. Similarly, cost savings of 38, 35 and 36% respectively were obtained. A trade-off was noted between the energy costs and the other components of the objective function since more energy was required to facilitate the reduction of water consumption and capital requirements.

Assessment of the Potential of Using Nanofiltration Polymeric and Ceramic Membranes to Treat Refinery Spent Caustic Effluents

Spent caustic effluents are very challenging due to their very hazardous nature in terms of toxicity as well as their extreme pH (approximately 12–14). Spent caustic has presented a challenge for wastewater treatment in refineries, due to its composition rich in mercaptans, sulfides and other aromatic compounds. To address such problems, membrane filtration was studied using real effluents from Sines Refinery, in Portugal. The present study attempts to assess the potential for spent caustic treatment with nanofiltration (NF) polymeric and ceramic membranes, assessing membrane life expectancy. For that, membrane aging studies in static mode were performed with the polymeric membrane before attempting NF treatment (dynamic studies). A ceramic membrane was also tested for the first time with this type of effluents, though only in dynamic mode. Although the polymeric membrane performance was very good and in accordance with previous studies, its lifespan was very reduced after 6 weeks of contact with spent caustic, compromising its use in an industrial unit. Contrarily to expectations, the ceramic membrane tested was not chemically more resistant than the polymeric one upon direct contact with spent caustic (loss of retention capacity in less than 1 h in contact with the spent caustic). The results obtained suggest that a pH of 13.9 is very aggressive, even for ceramic membranes.

Advances and Applications of Hollow Fiber Nanofiltration Membranes: A Review

Hollow fiber nanofiltration (NF) membranes have gained increased attention in recent years, partly driven by the availability of alternatives to polyamide-based dense separation layers. Moreover, the global market for NF has been growing steadily in recent years and is expected to grow even faster. Compared to the traditional spiral-wound configuration, the hollow fiber geometry provides advantages such as low fouling tendencies and effective hydraulic cleaning possibilities. The alternatives to polyamide layers are typically chemically more stable and thus allow operation and cleaning at more extreme conditions. Therefore, these new NF membranes are of interest for use in a variety of applications. In this review, we provide an overview of the applications and emerging opportunities for these membranes. Next to municipal wastewater and drinking water processes, we have put special focus on industrial applications where hollow fiber NF membranes are employed under more strenuous conditions or used to recover specific resources or solutes.

Treatment of petroleum wastewater contaminated with hydrocarbons and inorganics by anoxic-aerobic sequential moving bed reactors

The present study deals with the biotransformation of virulent petroleum refinery concoction with phenol (750 mg/L), emulsified crude oil (300 mg/L), S^2- (750 mg/L), NH₄⁺-N (350 mg/L) and NO₃^--N (1000 mg/L) in anoxic (A1) - aerobic (A2) moving bed reactors operated in series. The efficacy of the system was analysed through measurement of pollutant concentrations, GC-MS and FTIR peaks of the influent and effluent, and biomass activity studies. The system was able to eliminate the organics and inorganics with more than 99% efficiency at 80 h HRT and 64 h cycle time. GC-MS results revealed breakage of high molecular weight organics to smaller compounds after anoxic treatment. Further treatment of anoxic effluent by aerobic biomass reduced the number of peaks in the final effluent significantly. FTIR results were in accord with the GC-MS results. Heterotrophic activity (HA) of the aerobic biomass was higher than anoxic biomass due to its higher free energy change. Anoxic biomass showed chemolithotrophic activity (CA), suggesting survival in the absence of organics. Gas generated from anoxic reactor consisted of 91% nitrogen, 1% CO₂, 1% H₂S and rest was unaccounted.

Reverse osmosis performance on stripped phenolic sour water treatment - A study on the effect of oil and grease and osmotic pressure

Technologies for water recycling within oil refineries have been gaining interest at an extensive rate due to the large volume of wastewater generated, high dependency of water and the progressive scarcity of this valuable resource. Phenols are part of a specific class of organic pollutants that have been contributing to a low-quality effluent in oil refineries due to their hazardous nature and strict environmental legislation associated. The reuse of stripped sour water within refineries is often blocked due to its rich phenolic content. This study evaluates the retention of phenols in refinery wastewater through reverse osmosis (RO) at its major source of emission, for water reclamation. The RO membrane selected exhibited rejections of up to 98% of phenols and 99% of both chemical oxygen demand (COD) and total organic carbon (TOC). Permeate quality remained intact despite flux decline caused by phenolic and hydrocarbon adsorption when the oil content, in the feed, reached 771 ppm. The effluent's low conductivity due to lack of salts led to minor osmotic pressure differences (less than 2.5 bar at a volume concentration factor of 3), therefore, showing appealing performances of reverse osmosis filtration. Characterization of all permeates obtained from cross-flow filtration experiments showed COD levels in line with water reuse quality standards for make-up water in cooling processes.

Simulation for the Performance and Economic Evaluation of Conventional Activated Sludge Process Replacing by Sequencing Batch Reactor Technology in a Petroleum Refinery Wastewater Treatment Plant

Treatment of the petroleum refinery wastewater containing complex chemicals using biological processes is usually challenging because of the inhibition and/or toxicity of these matters when they serve as microbial substrates. In addition, performance modeling and cost evaluation of processes are essential for designing, construction, and forecasting future economic requirements of the petroleum refinery wastewater treatment plants (PRWWTPs). In this study, the performance and economics of conventional activated sludge (CAS) process replacing by sequencing batch reactor (SBR) technology in a two train PRWWTP were evaluated using simulation. The final treated effluent characteristics for the PRWWTPs containing CAS + CAS and SBR + CAS processes under steady state conditions were studied and evolution of the main parameters of the final effluent during the 30 days of simulation for these plants were investigated. Finally, the total project construction, operation labor, maintenance, material, chemical, energy, and amortization costs of these plants were estimated and compared. Results demonstrated that the project construction cost of PRWWTP containing CAS + CAS processes was lower than that of PRWWTP containing SBR + CAS processes and the energy and amortization costs for both plants were higher in comparison with the operation, maintenance, material, and chemical costs. Note that this study is a computer simulation and drawing general conclusions only on the basis of computer simulation may be insufficient.

Integrated interrogation of causes of membrane fouling in a pilot-scale anoxic-oxic membrane bioreactor treating oil refinery wastewater

Studies on membrane fouling during treatment of oil refinery wastewater (ORW) via membrane bioreactor (MBR) are currently lacking, and associated fouling challenges are largely undocumented. Using advanced chemical and Illumina sequencing approach, we investigated the complex bio-physiochemical interactions responsible for foulant-membrane interactions during treatment of ORW. After nearly 2 months of the MBR operation, COD removal reached maximal of 97.15 ± 1.85%, while oil and grease removal was maintained at 96.6 ± 2.6%, during the treatment duration. Most of the less or non-biodegradable oil moieties (>0.5 μm) progressively accumulated on the membrane as the influent oil concentration increased. Presence of relatively higher unsaturated extracellular polymers (100.6 mg/g VSS) like fulvic acid and aromatic-like compounds at high volumetric loading (~18.7 kg COD/m³/d), enhanced the adsorption of chemical elements (Fe = 88.9, Al = 63.4, and Ce = 0.56 mg/g dry-sludge, respectively). Moreover, shift in microbial community structure to hydrocarbon-utilizing and metals-tolerating genera, as Comamonas and Rhodanobacter, respectively, uncovers major membrane colonizers in ORW treatment via MBR.