Effects of Sludge Concentration and Disintegration/Solubilization Pretreatment Methods on Increasing Anaerobic Biodegradation Efficiency and Biogas Production

It is urgent to determine suitable municipal sludge treatment solutions to simultaneously minimize the environmental negative impacts and achieve sustainable energy benefits. In this study, different sludge pretreatment techniques were applied and investigated to enhance the sludge solubility and, subsequently, facilitate the anaerobic biodegradation performance of the mixed sludge under different sludge concentrations and pretreatment techniques. The sludge characteristics before and after pretreatment and batch experiments of anaerobic digestion of sludge samples under different conditions were analyzed and discussed. The results showed that the mechanical pretreatment method, alone and in combination with low-temperature heat treatment, significantly improved the sludge solubility, with the highest solubility at 39.23%. The maximum biomethane yield achieved was 0.43 m3/kg after 10 d of anaerobic digestion of a 3% sludge sample subjected to mechanical and thermal pretreatment prior to anaerobic biodegradation. In comparison, it took more than 28 d to achieve the same biomethane production with the unpretreated sludge sample. Mechanical pretreatment and subsequent heat treatment showed a high ability to dissolve sludge and, subsequently, accelerate anaerobic digestion, thereby providing promising prospects for increasing the treatment capacity of existing and new sludge treatment plants.

Assessment of Sludge Sample as a Feedstock for Power Generation

Treatment and disposal of sewage sludge has become an economically and environmentally sensitive problem. This necessitates cost-effective and innovative solutions whilst responding to environmental regulation and public pressures. This study examines the characteristics of a typical sludge samples as received following standard analytical procedures and its suitability for power generation. The results of the analysis revealed that the sample has good proxanal and ultanal attributes. The higher heating value of the sample on dry basis was found to be 21.21 MJ/kg. These characteristics are similar to qualities of standard coal used as fuel in power stations.

Downhole Sludge: Formation, Characterization and Removal

Sludge formed downhole in the production interval can be classified into crude oil-based or mud-based sludge. Sludge obstruction may result in partial or total loss of well productivity. Oil-based mud is commonly used in drilling of the pay zones in sandstone formations as a less/non damaging fluid. Oil-based mud typically contain emulsifier, viscosifer and other additives including polymer blend and calcium carbonate to serve different functions. Presence of emulsifier may increase emulsion tendency upon interaction with downhole environment. The resulting emulsion might be tight to an extent that a thick sludge is formed which can impair well productivity. Similarly, oil-based sludge may form from oil/water interaction in presence of emulsifiers, asphaltene, wax, solids, shear, etc. Identification of the sludge material will help in development of an effective chemical treatment to remove formation damage and restore well productivity. In this study, an extensive laboratory work was conducted to explore potential interactions of different downhole environment contaminants/factors on formation of oil-based and mud-based sludge. Typical mud-based and crude oil-based sludge samples were characterized using different analytical techniques including solvent extraction, XRD, TGA, ICP and viscosity. The results showed that the mud-based sludge sample contained calcium carbonate, dolomite quartz as the main components in the inorganic phase while the organic phase include polymers and oil. The oil-based sludge sample contained mainly water (82 wt%) with some solid particulates and asphaltene in the organic phase. Analysis of supernatants generated from solubility tests conducted for the mud-based and oil-based sludge samples revealed in addition to the high amount of calcium presence of iron in considerable amount (nearly 1,000 mg/L). Interaction of ferric chloride, quartz with an invert-emulsion mud was investigated. A significant increase in viscosity was observed upon incorporation of these contaminates with the mud sample. Iron ions in the aqueous phase tended to stabilized emulsion. This paper presents in detail mechanisms of mud-based and crude oil-based sludge formation upon interaction with environment. It also examined several chemical formulations for removal of mud-based and oil-based sludge samples.

A new energy-positive technological approach for wastewater treatment and bioenergy generation using a photo anoxic baffled reactor (PABR)

This study proposed a new energy-positive technological approach for wastewater treatment and bioenergy generation using an algal–bacterial symbiosis system in a photo anoxic baffled reactor (PABR). The PABR consisted of a sedimentation chamber, four regular baffled chambers, and two floated filter media chambers. The PABR was operated in the presence of natural sunlight with an average intensity of 30 µmoles/m2/s. A wide range of ORP (−215 to 255 mV) data suggested that a suitable environment condition existed in the PABR for photosynthesis, nitrification, and denitrification. Simultaneous nitrification/denitrification (SND) was observed in the first three chambers, and microbial assimilation was governed in the last four chambers. An average biochemical oxygen demand (BOD), NH3–N, total nitrogen (TN), and PO43− removal efficiencies were more than 88, 48, 36, and 42%, respectively. Moreover, hydrothermal liquefaction (HTL) was carried out for sludge and microalgae samples for bioenergy (e.g., biocrude and biochar) conversion, where the sludge sample containing microalgae and bacteria was collected from PABR and microalgae sample was collected from photobioreactor. Finally, the Fourier transform infrared spectroscopy (FTIR) analysis was done for both biocrude and biochar derived from sludge and microalgae samples, and it was suggested that the biocrude and biochar derived from sludge sample were better than that of microalgae sample.

Hydrometallurgical processing of technogenic finely dispersed fluorocarbon-containing raw materials of primary aluminum production

The purpose of the paper is to determine the conditions for the maximum transition of fluorine from the technogenic raw materials of primary aluminum production (mature sludge) into solution under alkaline leaching. The object of research is the mature sludge, which is formed from technogenic finely dispersed materials of aluminum production in the baths with Soderberg anodes (tailings of coal foam flotation, gas cleaning sludge, electrostatic precipitator dust) and stored close to the enterprise. Analytical studies of the initial sample and leaching products have been carried out according to the certified methods using chemical, X-ray phase and titrimetric analysis methods. It is shown that, the main percentage of the three sludge components belongs to the dust of electrostatic precipitators (~ 79.7%) and coal foam flotation tailings (~ 15.8%). It has been determined that the gas cleaning sludge features the richest composition of useful components (in the sum of F, Na and Al ~ 63%). According to the data of X-ray phase analysis, the sludge sample from the sludge storage mainly contains cryolite (up to 78.7%), carbon (11.9%), calcium-magnesium carbonate from the dolomite series (4.44%), and trace amounts of corundum and fluorite. The results of the conducted experiments on fluorine leaching from the sludge sample by the caustic soda solution allow to estimate the main process parameters: temperature - 75–80°С, duration - 60 min, NaOH concentration - 3.0% (with the W:T ratio of 10:1 and a stirrer speed of ~ 1005– 1010 rpm). According to the analytical data on the chemical composition of leaching cake, the fluorine content in the solid phase reduces by 88.1%. The experiments carried out on alkaline leaching of fluorine from the sample of mature sludge formed under primary aluminum production by the electrolysis of cryolite-alumina melts in the baths with self-baking anodes allowed to find out that the maximum decrease of fluorine content in the sample is achieved under the conditions of maintaining the process parameters including temperature, duration, reagent concentration in optimal modes.

Microplastic contamination in a conventional wastewater treatment plant in Thailand

Plastic waste has become a global environmental concern. One type of plastic waste is microplastics (MPs), which can spread easily in the environment. Wastewater effluent is one of the land-based sources of MPs. This study investigates the amount of microplastic (MP) pollution in an urban wastewater treatment plant (WWTP) in Thailand. Water samples were collected and examined to find the types, morphology and sources of MPs. Wastewater was filtered through a set of sieves ranging from 5 mm to 0.05 mm. Sludge samples were also collected to find the potential risk from the application of dried sewage sludge. Fourier-transform infrared spectroscopy (FTIR) was used to confirm the types of MPs. The amount of MPs in the influent was 26.6 ± 11.8 MPs/L. More than one-third of MP particles were removed after a grit trap, followed by 14.24% removal in the secondary treatment. If the peak flow rate of the WWTP is reached, 2.32 × 109 MP particles can be released daily. The amount of MPs in a sludge sample was 8.12 ± 0.28 × 103 particles/kg dry weight. Dry sludge is one of the potential sources of MP contamination in agricultural soil. Most MPs in the liquid fraction and sludge sample were fibres. Results from FTIR analysis showed that the major types of MPs in the WWTP were polyester fibres, followed by polypropylene, polyethylene, silicone polymer and polystyrene. This finding indicates that a conventional WWTP may act as a path by which MPs enter the environment.

Energy and Resource Utilization of Refining Industry Oil Sludge by Microwave Treatment

The oily sludge from crude oil contains hazardous BTEX (benzene, toluene, ethylbenzene, xylene) found in the bottom sediment of the crude oil tank in the petroleum refining plant. This study uses microwave treatment of the oily sludge to remove BTEX by utilizing the heat energy generated by the microwave. The results show that when the oily sludge sample was treated for 60 s under microwave power from 200 to 300 W, the electric field energy absorbed by the sample increased from 0.17 to 0.31 V/m and the temperature at the center of the sludge sample increased from 66.5 °C to 96.5 °C. In addition, when the oily sludge was treated for 900 s under microwave power 300 W, the removal rates were 98.5% for benzene, 62.8% for toluene, 51.6% for ethylbenzene, and 29.9% for xylene. Meanwhile, the highest recovery rates of light volatile hydrocarbons in sludge reached 71.9% for C3, 71.3% for C4, 71.0% for C5, and 78.2% for C6.

Vitreimonas flagellata gen. nov., sp. nov., a novel member of the family Hyphomonadaceae isolated from an activated sludge sample

A coccobacilli-shaped proteobacterium, designated strain SYSU XM001T, was isolated from an activated sludge sample collected from JiMei sewage treatment plant, Xiamen, PR China. Cells were Gram-stain-negative, catalase-positive and oxidase-negative. The 16S rRNA gene sequence of strain SYSU XM001T shared less than 92 % sequence identities with members of the class Alphaproteobacteria , with highest sequence similarity to Aquidulcibacter paucihalophilus TH1-2T (91.6 %; family Hyphomonadaceae , order Rhodobacterales ). The strain exhibited growth at 25–37 °C, pH 7.0–9.0 and in the presence of up to 1 % (w/v) NaCl. Its chemotaxonomic features included ubiquinone-10 as the respiratory isoprenologue, iso-C16 : 0, 10-methyl C16 : 0 TSBA and anteiso-C17 : 0 as major cellular fatty acids and monoglycosyldiglyceride, glucuronopyranosyldiglyceride and two unidentified glycolipids as the main polar lipids. The DNA G+C content was determined to be 62.9 % (draft genome). Analyses of the phylogenetic data and differences in the chemotaxonomic and biochemical features from related genera in the family Hyphomonadaceae indicated that strain SYSU XM001T merits representation of a novel species of a novel genus, for which the name Vitreimonas flagellata gen. nov., sp. nov. is proposed. The type strain of Vitreimonas flagellata is SYSU XM001T (=CGMCC 1.16661T=KCTC 62915T).

Adsorption and Desorption Study of Locally Available BOF Sludge to Remove Metal Ions from Aqueous Solutions

Coarse BOF sludge is a waste originating from steelmaking production. The major phaseof this waste is zinc ferrite. BOF sludge for this study was obtained from the metallurgical industryfrom a process of gas treatment in an oxygen converter. The sorption of cobalt, manganese and nickelions was investigated in the sample of the deposited sludge in a batch of experiments. The sorptionprocess was evaluated using three types of isotherm models. The sludge sample was alkaline andconsisted primarily of X-ray amorphous compounds and crystalline Fe oxides. The adsorptionprocess showed that a high removal efficiency was achieved at a lower initial concentration of metalions. Moreover, the equilibrium of the sorption process was achieved after 72 hours. Subsequently,the desorption of these adsorbed ions was investigated. The results of this study indicate that theapplication of metallurgical waste as a sorbent is highly effective for the treatment of wastewater.