Bottom Sludge Research Articles

Hydrothermal Carbonization of Crude Oil Tank Bottom Sludge for Energy Applications

Hydrothermal Carbonization of Crude Oil Tank Bottom Sludge for Energy Applications

Screening oil tank bottom sludge microbial community for identification of native efficient hydrocarbon-degrading bacteria for bioremediation purposes

Screening oil tank bottom sludge microbial community for identification of native efficient hydrocarbon-degrading bacteria for bioremediation purposes

Utilizing sludge from catfish farming to produce vermicompost for improving soil quality

Abstract Earthworm organic waste is processed into vermicompost, which is of varying quality depending on the substrate. In vermicomposting, earthworms can promote nitrogen mineralization and effect nitrification. A challenging-to-absorb nutrient will be converted into a nutrient that plants can easily absorb to improve nutrients in soil and increase crop production. In this study, an experimental model of organic fertilizer production from catfish pond bottom sludge was implemented. Sludge from the bottom of catfish ponds is composted with water hyacinth in aquatic ponds to produce organic fertilizer, mature fertilizer is used as a substrate for vermicomposting. The impact of vermicompost on plant growth parameters was evaluated through its use to improve nutrients in soil. Sludge, compost, vermicompost, and soil quality were also evaluated for their physical and chemical properties. Results show that the growth coefficient of earthworms is 129.3±1.15% per 30 days, and the average amount of organic fertilizer created is 126±3.51 kg per 30 days. The quality parameters of vermicompost all meet national standards for organic fertilizer quality. The moisture and total organic matter content in mature fertilizer are 31% and 21.9%, respectively. The content of nutrients N and P increased compared to input materials, the corresponding values reached 2.84% and 0.96%. The C/N ratio is 7.7, microbiological and heavy metal indicators are within the accepted limits. In the experiment using vermicompost to cultivate Brassica rapa chinensis, the yield growth rate was the highest. After 21 days of planting, the growth rate is fast and the height reaches 25.0±0.38 cm. The biochemical composition ensures safety according to food regulations for leafy vegetables. Vermicomposting is recommended as a sustainable and suitable technique for catfish pond sludge utilizing.

Nitrogen removal performance and the biocenosis with microalgae consortium Nitrosifying and anammox bacteria in an upflow reactor

This study introduced an innovative pathway utilizing an algal anaerobic ammonium oxidation (ALGAMMOX) system to treat ammonium wastewater. Lake bottom sludge and anammox sludge were used to cultivate functional microorganisms and microalgae for nitrogen removal in an upflow reactor made of transparent materials. The results showed that the ALGAMMOX system achieved 87.40 % nitrogen removal when the influent NH4+-N concentration was 100 mg-N/L. Further analysis showed that anammox bacteria Candidatus Brocadia (8.87 %) and nitrosobacteria Nitrosomonas (3.74 %) were crucial contributors, playing essential roles in nitrogen removal. The 16S rRNA gene showed that the anammox bacteria in the sludge transitioned from Candidatus Kuenenia to Candidatus Brocadia. The 18S rRNA gene revealed that Chlamydomonas, Bacillariaceae and Pinnularia were the dominant microalgae in the system at a relative abundance of 7.99 %, 3.64 % and 3.14 %, respectively. This novel approach provides a theoretical foundation for ammonium wastewater treatment.

A method for predicting tank bottom sludge formation during crude oil storage

The laboratory method for predicting the amount and composition of sludge accumulated during crude oil storage on the bottom of a high capacity storage tank has been developed and tested. The laboratory model of the storage tank on a scale of 1:20 was designed with the assumption of a 20-fold acceleration of the process of sedimentation of wax particles and, thus, the formation of a bottom sludge. The results of the model and industrial scale (in the high capacity tank) storage of a Russian export blend crude oil were compared and excellent agreement was found. The developed method was used to evaluate an Iran Light crude oil and a blend of crude oils, Azeri Light, and CPC. The diametrically different behaviour of the compared crude oils during their model storage was ascribed to the different paraffinic particles size distributions and rheologic properties. The correlation between the composition of the crude oil and its tendency to form a sludge at the bottom of the storage tank was not found.

Evaluation of Water and Sediment Quality in Lake Mogan, Türkiye

The wetlands, with their delicate ecosystems, play a crucial role in regulating water regimes and supporting diverse plant and animal communities, particularly those associated with water habitats. Mogan Lake, located within the Gölbaşı Special Environmental Protection Area, stands out as a unique habitat, hosting over 200 bird species. This study aimed to assess the current water quality of Mogan Lake by analysing various water quality variables. Three sampling sites, representing the northern, middle, and southern parts of the lake, were selected to examine both surface water and bottom sludge characteristics through the analysis of 29 pollutant variables. Water samples were collected from 30 cm beneath the water surface and 50 cm above the bottom of the lake. Sediment samples were collected from the sludge at the lake basin. Additionally, to understand their impact on the lake’s water quality, 26 pollutants were also measured in water samples taken from the five main streams that feed the lake. The results reveal a significant level of organic pollution in the lake, along with elevated nitrogen levels indicating hypertrophic conditions. Although organic pollutants were detected in the lake bottom sediment through analysis, they are considered non-hazardous in terms of heavy metals and other inorganic variables.

Anaerobic sludge from a full-scale biodigester: physico-chemical and organic characterization, and principal component analysis (PCA)

The biological transformation of the organic fraction of municipal solid waste into bioenergy yields a solid digested material known as anaerobic sludge, comprising a mixture of organic and inorganic substances. This sludge holds significant potential as a renewable resource for agricultural reuse. However, there is also the potential risk of contamination from this material in receiving environments. Therefore, it is crucial to assess the characteristics of this material to ensure compliance with local regulations regarding its soil application, aiming to avoid adverse environmental impacts and ensure proper and viable disposal. In this study, conducted to explore the characteristics of bottom sludge collected from a pilot-scale anaerobic biodigester, various parameters were analyzed. The biodigester in question had a capacity of 1300 liters and a useful volume of 1000 liters, digesting food waste and water hyacinth (Eichhornia crassipes) in a ratio of 20% in terms of volatile solids from the macrophyte to the volatile solids of the food waste. A multivariate analysis was conducted on the following parameters: metals (Al, Ba, Cd, Cr, Cu, Fe, Mn, Mo, Pb, Se, V, Zn, Na, and K); total, fixed, and volatile solids; alkalinity; volatile fatty acids; ammonia; Kjeldahl nitrogen (NTK); and organic, inorganic, and total carbon (COT), to observe possible correlations among these parameters. Additionally, the sludge underwent nuclear magnetic resonance (NMR) analysis for detection and characterization of organic compounds. This approach provided a deeper understanding of the properties of anaerobic sludge produced strictly under the aforementioned conditions, contributing to further research in the field.

Coculture of abalone (Haliotis midae) and sea cucumber (Neostichopus grammatus) to reduce tank cleaning frequency in abalone farming

Abalone farming produces nutrient-rich sludge, and the frequent cleaning and removal of sludge from abalone tanks is labour and capital-intensive. This study aimed to assess the effect of culture methods and tank cleaning frequency on abalone growth, water quality, and sludge characteristics. The study was conducted for 16 weeks. Four treatments were used, namely, abalone cocultured with sea cucumber cleaned once (AS1) and twice weekly (AS2); abalone monoculture cleaned once (A1) and cleaned twice weekly (A2). Abalone (initial avg weight = 40.9 g) were maintained under commercial stocking conditions in flow through systems at a salinity of 35 ppt and fed a commercial formulated diet (Abfeed™) and fresh seaweed (Ulva lacinulata and Gracillaria gracilis). The stocking densities were 200 abalone m−2 and 50 sea cucumbers m−2. The sea cucumbers (initial average weight = 12.5 g) fed on the abalone faeces and leftover feed, which settled at the abalone tank's bottom (sludge). There was a significant interaction between the type of culture and the frequency of cleaning on abalone weight (F (1,476) = 12.41, p < 0.001). Abalone in the A2 treatment group showed higher growth (p = 0.006) than those of the A1 treatment group, while abalone in AS1 had significantly higher growth (p < 0.001) than those in the AS2 treatment group. Also, abalone in AS1 showed higher growth (p = 0.026) than abalone in the A1 treatment. However, abalone in AS1 had growth similar (p = 0.53) to those in A2. The survival rate of the sea cucumbers was high, however, the sea cucumbers experienced a reduction in weight regardless of the treatment. This study showed that growth optimisation in abalone farming can be achieved by cleaning tanks twice instead of once weekly. However, when abalone are cocultured with sea cucumber, tanks need only be cleaned once a week without compromising abalone growth or water quality. The coculture of abalone and sea cucumber results in an additional aquacultured product, a significant reduction in labour and other associated costs of cleaning, without an additional cost of production.

Petroleum sludge formation and its treatment methodologies: a review.

Different petroleum operations produce huge amount of oil sludge annually. For instance, US EPA estimates the annual sludge production of each US refinery of 30,000 tons, while the average oily sludge produced from petrochemical industries in China is estimated about 3 million tons per year. In the last year, our center could recover about 30,206 barrels of raw oil from 32,786 barrels of tank bottom sludge (TBS) for different petroleum companies. This sludge causes huge economic losses besides its negative environmental impacts. The accumulation of sludge in the tanks results in reducing the tanks' capacity for storing liquid crude, accelerating the corrosion of the tanks, delay in the production schedule, and disturbing the whole production operation. There are diverse treatment methodologies such as solvent treatment, addition of certain chemicals, and centrifuging. Of course, the environmental regulations and the overall cost limitations are very important in deciding the preferred applicable method(s). Although several works handled the problem of sludge deposition and treatment from different aspects, we intend to introduce a different work. First, composition, formation, types, and properties of TBS were reviewed. Then, environmental and economic problems caused by TBS were revised. At last, different methodologies applied for treatment of oily TBS to recover oil and safe disposal of hazardous remains were investigated focusing on the most straightforward and environmentally friendly protocols. It is expected that this review attracts the experts in petroleum chemistry, and other relevant fields and provides a comprehensive understanding of current sludge control and treatment research.

Natural convection in two-layer channel near bottom sludge under the influence of daily temperature fluctuations by the Lattice Boltzmann Method

This study investigates the natural convective flow within an horizontal two-layer system driven by daily temperature fluctuations. The upper part of the layer is free of the porous medium, while the porosity is in the lower part. A homogeneous porosity distribution is assumed along the bottom, mimicking the flow near bottom vegetation or sludge. The Lattice Boltzmann Method is employed to solve the problem. The porous medium is simulated using the representative elementary volume (REV) method. An additional set of distribution functions is implemented to capture temperature distribution. Simulation is performed at constant porosity coefficient and at different Darcy number.

High phenanthrene degrading efficiency by different microbial compositions construction.

Microbial remediation has become the most promising technical means for the remediation of polycyclic aromatic hydrocarbons (PAHs) non-point source contaminated soil due to its low cost of treatment, complete degradation of pollutants, and in-situ remediation. In this study, in order to demonstrate the phenanthrene degrading microbial diversity, phenanthrene was chosen as the representative of PAHs and strains capable of degrading phenanthrene were isolated and screened from the sedimentation sludge and the bottom sludge of oil tank trucks, and high throughput sequencing was used to check the dominant strains with a good degrading effect on phenanthrene. Results showed even more than 50% of phenanthrene was degraded in all samples, the composition of PAH-degrading bacteria was diverse, and different environments constructed different functional microbial groups, which resulted in the microbial adapting to the diversity of the environment. Finally, a series of bacterial species with phenanthrene-degrading functions such as Achromobacter, Pseudomonas, Pseudochelatococcus, Bosea was enriched after nine transferring process. Overall, our study offers value information for the enrichment of functional degrading microbes of phenanthrene or other pollutants that more concern should be paid in not only the degradation rate, but also the diversity variation of microbial community composition.

Analysis of surfactant production by Bacillus cereus GX7 and optimization of fermentation conditions

Although biosurfactants have many advantages compared to chemical surfactants, biosurfactants are still limited by problems such as low yields and high production costs. In the present study, a strain of Bacillus Cereus (GX7) isolated from an oil tank bottom sludge of Shengli Oil Field (China) was selected as a highly effective surfactant producer. The biosurfactant produced by GX7 was extracted, purified, and analyzed by TLC, FT-IR, and LC-MS/MS. The results showed that the biosurfactant was surfactin of lipopeptide surfactant. Single-factor experiments were used to optimize the fermentation process of the strain from two aspects: the composition of the fermentation medium (carbon source, nitrogen source) and the fermentation conditions (temperature, pH, inoculation amount, rotation speed, and fermentation time). The surface tension and emulsification index of the fermentation broth were used to evaluate the optimal fermentation conditions. The results showed that the best carbon and nitrogen sources were glucose and peptone, and the optimum temperature, inoculum amount, pH, rotation speed, and fermentation time were 30 ℃, 1%, 7.5, 150 rpm, and 48 h, respectively. After optimization, the surface tension and emulsification index of fermentation broth were 26.84 mN/m and 57.84%, respectively. Moreover, the results also prove that the biosurfactant produced by this strain has good stability in a wide range of temperature, pH, and salt concentration.

Plate Load Tests of Soft Foundations Reinforced by Soilbags with Solid Wastes for Wind Farms.

Soilbags are expandable three-dimensional geosynthetic bags made from high-density polyethylene or polypropylene. This study conducted a series of plate load tests to explore the bearing capacity of soft foundations reinforced by soilbags filled with solid wastes based on an onshore wind farm project in China. The effect of contained material on the bearing capacity of the soilbag-reinforced foundation was investigated during the field tests. The experimental studies indicated that soilbag reinforcement with reused solid wastes could substantially improve the bearing capacity of soft foundations under vertical loading conditions. Solid wastes like excavated soil or brick slag residues were found to be suitable as contained material, and the soilbags with plain soil mixed with brick slag had higher bearing capacity than those with pure plain soil. The earth pressure analysis indicated that stress diffusion occurred through the soilbag layers to reduce the load transferred to the underlying soft soil. The stress diffusion angle of soilbag reinforcement obtained from the tests was approximately 38°. In addition, combining soilbag reinforcement with bottom sludge permeable treatment was an effective foundation reinforcement method, which required fewer soilbag layers due to its relatively high permeability. Furthermore, soilbags are considered sustainable construction materials with advantages such as high construction efficiency, low cost, easy reclamation and environmental friendliness while making full use of local solid wastes.

Process modelling and optimisation of methane yield from palm oil mill effluent using response surface methodology and artificial neural network

Methane yield plays an important role in evaluating the performance of anaerobic digestion (AD) process due to fluctuating characteristics of palm oil mill effluent (POME). In this study, two years of industrial-scale plant data collected from biogas plant in Pahang, Malaysia consisting of methane yield and H2S concentration were modelled using supervised Machine Learning (ML) algorithms, i.e. artificial neural network (ANN) and response surface methodology (RSM). Input parameters appraised were pH, temperature, and recirculation ratio (RR) of total treated effluent and bottom sludge to raw POME. Fitness of all models was evaluated based on performance metrics, namely determination coefficient (R2) and root mean square error (RMSE). Results demonstrated that ANN was superior to RSM model with R2 of 0.9762 and 0.8500, respectively. Besides, three-dimensional (3-D) response surface plot was utilised to study interactive effects between AD parameters on methane yield. Temperature and recirculation ratio (RR) was found to be main interactive factor of methane yield which was corroborated using Pareto chart. Process optimisation using RSM revealed that the highest methane yield was 0.2733 N m3 CH4/kg CODremoved (i.e. improvement percentage of 9.3%) with the least H2S concentration of 1086.4 mg/L under optimum operating conditions, i.e. temperature, pH and RR of 42 °C, 7.36 and 2.5, respectively. Sensitivity analysis revealed that RR plays substantial roles in yielding more methane in AD process. Maintaining RR ratio at optimum level (1.05 to 2.60) is key to achieve high methane yield with good stability by considering the trade-off between operating cost and revenue of biogas plant.

Study of synergetic effect of green chemicals on dissolution of tank bottom sludge

Study of synergetic effect of green chemicals on dissolution of tank bottom sludge

Speciation, bioaccessibility and human health risk assessment of chromium in solid wastes from an ultra-low emission coal-fired power plant, China

Chromium (Cr) in solid wastes from ultra-low emission (ULE) coal-fired power plants (CFPPs) could engender adverse effects on environment and human health. Hence, solid waste samples containing bottom ash, fly ash, gypsum and sludge were collected from a typical ULE CFPP in China to study the distribution, speciation, bioaccessibility and human health risk of Cr. The results showed that Cr was depleted in gypsum, whereas significantly enriched in bottom ash, fly ash and sludge comparing with feed coal. The ratios of Cr(VI) to total Cr in solid wastes were relatively low, but the increase of flow fractions in Cr chemical binding forms implied the deterioration of environmental stability. Based on the in vitro simulated digestion methods of solubility bioavailability research consortium (SBRC) and physiologically based extraction test (PBET), the bioaccessibility of Cr in the gastric and intestinal phases reached the highest values in either gypsum or sludge. After incorporating bioaccessibility in human health risk assessment, the carcinogenic risk (CR) within acceptable limits of Cr in solid wastes to adults and children was concluded, with the non-carcinogenic hazard quotient (HQ) was all within the safety threshold. The Monte Carlo model was applied to evaluate the uncertainty analysis of human health risk assessment at 5% and 95% confidence interval, and the fitting results were consistent with the calculation results of the carcinogenic and non-carcinogenic risk for adults and children. This study is expected to provide insights for the integration of bioaccessibility into the health risk assessment of Cr in solid wastes from ULE CFPPs, thus is conducive to the disposal of solid wastes and human health protection.

Influence of Different Types of Dewatering Agents on the Solidification Effect and Physical and Chemical Properties of Sediment

In order to study the comprehensive effects of different types of dehydrating agents on the dewatering and solidification of dredged sediments, this study took the dredged sediments of Taihu Lake as the research object and selected microorganisms, polymeric iron aluminum salts, organic polymers, organic-inorganic composites, and aluminum salt microorganisms. These five types of composite dehydrating agents were used to conduct a three-month solidification test on the dredged sediment by means of geotechnical pipe bag solidification. The results of the study showed that the dehydration efficiency of organic polymers and organic-inorganic composite chemicals was better. After one month, the water content of sediment dropped to 61.78% and 63.26%, respectively, which then dropped to 40.56% and 32.16% after three months. Compared with that of the unsolidified sludge, the total nitrogen of the bottom sludge after solidification by the organic-inorganic composite agent was reduced by 74.82%, reaching 591 mg·kg-1, primarily due to the reduction in ammonia nitrogen. The solid sludge contained mainly aluminum-bound phosphorus, calcium-bound phosphorus, and iron-bound phosphorus. Among them, four groups (organic-inorganic composite) had the largest reduction in active phosphorus, with the lowest being 64.3 mg·kg-1. In addition, organic polymer agents had the best curing effect on heavy metals, the comprehensive ecological risk index of heavy metals was reduced by 51.3%, and the leaching toxicity concentration was far below the standard threshold. This study showed that organic polymers and organic-inorganic composite medicaments have a better effect on the dehydration and solidification of bottom sludge and thus have good application prospects.

Effects of Ionic Liquid, 1-Ethyl-3-methylimidazolium Chloride ([EMIM]Cl), on the Material and Electrical Characteristics of Asphaltene Thin Films.

Asphaltene is a component of crude oil that has remained relatively unexplored for organic electronic applications. In this study, we report on its extraction technique from crude oil tank bottom sludge (COTBS) and its thin-film characteristics when 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) ionic liquid (IL) was introduced as dopants. The extraction technique yielded asphaltene with more than 80% carbon content. The IL resulted in asphaltene thin films with a typical root-mean-square surface roughness of 4 nm, suitable for organic electronic applications. The thin films each showed an optical band gap of 3.8 eV and a sheet resistance as low as 105 Ω/□. When the film was used as a conductive layer in organic field-effect transistors (OFET), it exhibited hole and electron conduction with hole (µh) and electron (µe) mobilities in the order of 10−8 and 10−6 cm2/Vs, respectively. These characteristics are just preliminary in nature. With the right IL, asphaltene thin films may become a good alternative for a transport layer in organic electronic applications.

STUDY ON THE ENVIRONMENTAL ASPECTS OF PIT CLOSURE GUIDELINES FOR OIL AND GAS PRODUCTION ACTIVITIES

Exploration, development, and production activities associated with oil and gas production projects can have a variety of impacts on the environment. A variety of wastes are produced by such activities. Apart from the wastewater that is in the form of produced water, many kinds of solid wastes are produced during exploration and production of oil and gas. These solid wastes, among others, are drilling mud and cuttings, and tank bottom oily sludge. These solid wastes are dumped temporarily in a certain place called a pit before they can be treated further. In order to minimize and possibly eliminate the environmental impacts of those solid wastes, pit construction has to be developed in such a way that release of pit contents to the environment could be prevented. In addition, pollutant loading of ground water from waste leaks, releases of hydrocarbons and hydrogen sulphide to the atmosphere are some of the factors that have also to be considered. As dumping such solid wastes in a pit is a temporary storage, pit closure management has also to be developed. Explicitly, governmental regulation concerning with environmental aspects of pit closure has not been established yet. Nevertheless, environmental management approach of pit construction and closure could be established by referring to the available regulation, namely Governmental Regulation PP. 18/1999 juncto PP. 85/1999 - hazardous waste regulation, and the related Ministerial Decree, such as Bapedal Decree No. Kep.-04/BAPEDAL/09/19995 decsribing methods of landfilling or land disposal for hazardous wastes. This approach is based on the reason that such solid wastes are also categorized as hazardous wastes. In regard to pit construction, study on pit location should include the hydrogeology pattern of the site. Furthermore, pit wall materials are parameters that also have to be considered in minimizing impacts to the surrounding. Upon closing the pit, a pit closure plans that call for the dewatering of mud and reserve pit contents before burial have to be developed to reduce the chance of the downward transport of contaminants to shallow aquifers. The grading of soils covering the pits may reduce the chances of infiltration of rainwater, which may migrate to ground water. Other consideration, for example revegetation, has also to be included. All of the above factors should be considered in pit closure and assessment guideline. In addition to the available national references, other worldwide references such as those of US-EPA guidelines deserve to be considered in studying pit management. The author has conducted a short study concerning pit closure management that has been implemented in oil and gas producing companies. Goals of the study are to review the manual guideline or standard operating procedure (SOP) of pit closure applied to the fields. The followings are report concerning with the implementation of the study.

Evaluation of sludge discharge methodologies in aerobic granular sludge reactors

We performed a comparison of different aerobic granular sludge (AGS) discharge methodologies in sequencing batch reactors (SBRs), evaluating the system efficiency, physical and microbiological characteristics of granules, and resource recovery of the discharged biomass. In R1, there was a selective discharge (30% top sludge and 70% bottom sludge, based on biomass weight) with SRT control (10–20 days). The same selective discharge was applied to R2, but with control of food to microorganisms (F/M) ratio (0.22–0.44 gCOD/gVSS·day). In R3, the discharge was conventional (similar to activated sludge reactors), i.e., mixed liquor during the aerobic period. Additionally, the best protocol of the lab-scale studies was used in a pilot-scale reactor (R4) treating municipal wastewater. R1 protocol was the best strategy for AGS formation, maintenance, and performance, achieving better removal efficiencies of COD (95%), total nitrogen (85%), and phosphorus (80%). Sludge discharge improved the system's performance and resource recovery, especially alginate-like exopolysaccharides (ALE).