River Sludge Research Articles

Enhanced separation of dual pollutants from wastewater containing Cr (Ⅵ) and oil via Fe-doped sludge derived membrane

One-step separation of multi-component contaminants in chemical separations by a single material is essential to simplify the separation process and enhance the separation efficiency. This work proposed an eco-friendly and effective “cation doping” strategy, utilizes waste river sludge (RS) as raw material, incorporates Fe to improve ion removal performance, and the Fe-doped RS/PVDF membrane was obtained for simultaneously removing Cr (Ⅵ) and oil from electroplating wastewater. The membrane exhibits outstanding rejection rates for oil (>98 %) and Cr (Ⅵ) (89.10 %), which was superior to Cr (Ⅵ) rejection rate of RS/PVDF membrane (22.04 %) without Fe doping under the combined action of electrostatic attraction, surface complexation, redox, and the superhydrophilic/underwater oleophobicity. Notably, protonation and low operating pressure contributed to Cr (Ⅵ) removal, and the membrane presents satisfactory acid-alkali resistance, anti-interference ions ability and chemical stability. Therefore, this work offers a novel development strategy for affordable and effective multifunctional separation membrane, and also promotes the realization of simultaneous and rapid removal of heavy metal ions and oil contaminants, which is encouraging in terms of potential industrial applications.

Rational Utilization of Sediment Resources Improves Rice Yield and Nitrogen Use Efficiency under Salt Stress

Soil salinization negatively affects rice growth and yield; however, how different sludge sources regulate rice growth and yield under salt stress was rarely investigated. This study evaluated the performance of two salt-tolerant rice cultivars, Chaoyou 1000 and Longliangyou 506, grown in two sediment sources, pond sediment (PS) and river sludge (RS), under salt stress (56 ds m−1 brine irrigation) with conventional soil (CS) used as the control. The results showed that the rice yield under the PS and RS treatments was enhanced by 51.0% and 43.6% as compared with CS, respectively, owing to an improvement in spikelet per panicle, 1000-grain weight, dry matter accumulation, and the chlorophyll content in both rice cultivars. Compared with CS, the total nitrogen accumulation, nitrogen grain production efficiency, nitrogen harvest index, and nitrogen partial productivity under the PS and RS treatments were increased by 18.9–28.9%, 17.0–20.6%, 7.2–16.6%, and 43.8–50.9%, respectively. Moreover, rice grown in PS and RS showed higher activities of nitrogen metabolism-related enzymes (nitrate reductase, glutamine synthetase, and glutamate synthetase) at the heading stage and higher K+ and K+/Na+ contents in the leaves. Overall, a balanced utilization of sediment resources (especially pond sediment) can effectively alleviate salt stress and improve the yield and nitrogen use efficiency in rice.

Investigation of the ionic curing effect and performance of modified nano-montmorillonite on river sludge pastes: Influence of sludge substitution and MNMt dosage

The effect of replacing cementitious materials with different dosages of river sludge on the properties of the cement-slag binary-based geopolymer composites was investigated. The application of this research is the possibility of reusing river sludge into environment-friendly unburned bricks. The influence of nano-montmorillonite on the solidification of heavy metals in the matrix was also explored. Samples containing sludge were characterized by lower fluidity and compressive strength, but prolonged hardening time; at 60% replacement, the strength was equal to 8 MPa and the final setting time was 4.5 h. The sample including 0.4% NMt helps to improve strength thanks to its ability to partially fill the capillary pores and promote the degree of hydration. The pastes containing NMt have less dangerous heavy metals like Cu (II) and Cr (VI). The reaction products and the microstructure of the mixes with modified-NMt are exploited to understand the mechanisms at the basis of the findings.

Biodegradation of phthalate isomers by newly isolated Klebsiella variico SY1 and its functional genomic analysis

Phthalate isomers (ortho-, meta-, and para-) are important industrial aromatic dicarboxylic acids and key intermediates of pollutants degradation such as waste polyethylene terephthalate (PET) and plasticizers. Recently, microbial treatment of such pollutants has been received much attention. In this study, Klebsiella variico SY1, which could simultaneously degrade three phthalate isomers, was isolated from river sludge. The degradation priority order of the three phthalate isomers was phthalate (PA), terephthalate (TPA) and isophthalate (IPA), and the tolerant concentration could reach 5500 mg/L. The degradation results showed that SY1 degraded 3000 mg/L of three isomers at the maximum rates of 186.38 mg/L∙h for TPA and 195.90 mg/L∙h for IPA, respectively. The analysis of comparative genome, key enzyme activity, gene expression and degradation intermediates, showed that SY1 initially degraded these three phthalate isomers to a common intermediate protocatechuic acid (PCA), and then accomplished a subsequent degradation through a bifurcated pathway. In addition, it was surmised that the ben gene cluster might also be involved in the degradation of phthalate isomers. In summary, Klebsiella variico SY1 was demonstrated as a chassis cell able to biodegrade phthalates and their derived contaminants due to its high degradation efficiency and tolerance against the three phthalate isomers.

Feasibility of agricultural utilization of river sludge as a planting substrate following treatment with polyacrylamide

Applying river sludge in agriculture is an effective way of recycling the beneficial substances it contains. Polyacrylamide (PAM) is widely used as a sludge dewatering flocculant and soil amendment agent. The objectives of this study were to determine the effects of PAM on sludge and to ascertain whether the PAM-treated sludge can be used as a planting substrate. Pot cultivation, infiltration, and leaching experiments were conducted under sludge treated with different amounts of PAM, and Chinese cabbage was also grown in pot experiments. We evaluated the changes in the nutrient and enzyme activities, aggregate stability, permeability of the sludge, the ability of the sludge to preserve water and nutrients, and Chinese cabbage growth. The results showed that the physiochemical characteristics of the sludge were improved by applying PAM. The pot experiment showed that the contents of alkaline hydrolysable N, NO3−, and NH4+ in PAM-treated sludge were increased significantly (p < 0.05) by PAM additions, and the optimum Chinese cabbage growth occurred with applications of 900 mg kg−1 and 1350 mg kg−1 PAM. The cultivation experiment showed that the catalase, alkaline phosphatase, and invertase activities were improved by adding PAM. The increased available nitrogen content in the sludge increased with the addition of PAM mainly because PAM provided a suitable micro-ecological environment for microorganisms to increase enzyme activity, which thus accelerated nutrient turnover. The infiltration and leaching experiments showed 900 mg kg−1 PAM provided the optimal permeability and aggregate stability, and better water and nutrient preserving effects. PAM improved the aggregate stability of river sludge by absorbing sludge particles to form larger aggregates, which improved the permeability, water, and nutrient preserving capacity of the sludge. Considering the improvement effects of PAM on the available nitrogen content, enzyme activity, aggregate stability, and water holding capacity of sludge while maintaining Chinese cabbage growth, we found that the 900 mg kg−1 PAM application was the best dosage.

Recycling of heavy metal contaminated river sludge into unfired green bricks: Strength, water resistance, and heavy metals leaching behavior – A laboratory simulation study

Recycling the sludge in building materials is a promising approach to reduce construction costs and environmental pollution. However, when the sludge is used as a raw material the mechanical properties and environmental risks of sludge should be taken into consideration. In this study, heavy metals contaminated river sludge (CRS) incorporated into the production of unfired green bricks with the combination of hemihydrate phosphogypsum (HPG), ground granulated blast furnace slag (GGBFS), and Portland cement (PC). The mechanical properties of brick specimens were determined by conducting unconfined compressive strength (UCS) and water resistance tests, while the hydration products and strength formation mechanism were detected by XRD, TGA, and SEM-EDS investigation. Furthermore, the TCLP and SPLP tests were used to assess the heavy metals releasing behavior. The explored results show that the UCS of samples increases with the rise of the replacement level of PC by GGBFS. The highest UCS and softening coefficient of bricks were 15.24 MPa and 0.94 using the combinations of 60% CRS, 20% HPG along with 17% GGBFS and 3% PC. The microstructural analysis revealed that HPG could react with GGBFS and PC to generate massive ettringite (AFt). These AFt may bridge gypsum crystals to form a dense network microstructure. Additionally, specimens prepared in this study exhibited an excellent fixing capacity for heavy metals. The heavy metal immobilization rates of the optimal mixture were all higher than 99.41%.

Effect of varying water content and extreme weather conditions on the mechanical performance of sludge bricks solidified/stabilized by hemihydrate phosphogypsum, slag, and cement

The accumulation of sludge in harbor and water channels causes serious environmental pollutions. The recycling of sludge into building materials compensates for the shortage of raw materials in the construction industry and mitigates the environmental impacts of sludge simulation. Therefore, in the current study, the waste river sludge (WRS) was solidified/stabilized by the combination of hemihydrate phosphogypsum (HPG), ground granulated blast furnace slag (GGBFS), and Portland cement (PC). The effect of different mixing proportions and WRS’s moisture content on the mechanical properties of specimens were investigated. Besides, the performance of prepared samples under extreme weather conditions, including acid/alkaline erosion, freeze–thaw cycling, and Na2SO4 immersion was systematically evaluated and discussed. The results show that the mechanical properties of solidified bricks increased with the incremental dosage of GGBFS and decreased with the rise of WRS’s moisture content. The acid/alkaline corrosion resistance and freezing-thawing resistance ability increased with the decrease of PC/GGBFS ratio due to the denser and tougher microstructure and the additional hydration and pozzolanic reactions of GGBFS. However, the inclusion of GGBFS accelerated the deterioration of specimens under Na2SO4 immersion.

БИОАУГМЕНТАЦИЯ АКРИЛАМИД-ДЕГРАДИРУЮЩИХ БАКТЕРИЙ В МИКРОБИОТЕ РЕЧНОГО ИЛА

Introduction. Bioaugmentation is an in situ bioremediation approach, which implies the introduction of a population of microorganisms with certain biodegrading abilities. Acrylamide is a biodegradable toxic substance. Our goal was to assess the survival of allochthonous bacterial cultures Alcaligenes faecalis 2 and Acinetobacter guillouiae 11h when introduced into river sludge and the efficiency of acrylamide decomposition by sludge with introduced amidase-containing bacteria. Methods. The microbiota of sludge from small rivers of Perm Territory was inoculated with the biomass of strains A. faecalis 2 and A. guillouiae 11h, which have amidase activity. In a laboratory experiment, we studied the survival of these bacteria as well as the biodegrading ability of the microbiota in relation to acrylamide after 3 and 6 months of incubation at 5 and 25°C. The transformation of acrylamide was assessed by HPLC, the biodiversity of river sludge was assessed by the method of metagenomic sequencing of 16S rRNA genes. Results. Incubation of sludge at 25°C for 3–6 months deteriorates the biodegrading abilities of the microbiota in relation to acrylamide, and the transformation of this pollutant occurs only during the augmentation of the biomass of amidase-containing bacteria, with acinetobacteria having an advantage over bacteria of Alcaligenes sp. Upon incubation of sludge at 25°C, the phylogenetic diversity increases, and the proportion of representatives of the phyla Actinobacteria, Chloroflexi, Ignavibacteriae, Candidatus Saccharibacteria, Acidobacteria increases as well, while the phylum Proteobacteria accounts for most of the bacterial biota in all samples, and the phylum Firmicutes accounts for 10–30%. The presence of representatives of Alcaligenes sp. and Acinetobacter sp. was confirmed in the microbiota of bioaugmented sludge after 6 months of incubation at 25°C. When incubated at 5°C, the microbiota of native sludge is capable of degrading acrylamide, but at a rate several times lower than during bioaugmentation. After incubation of Danilikha River sludge with the introduced biomass of strains A. guillouiae 11h and A. faecalis 2 at 5°C for 6 months, the complete transformation of acrylamide was observed in 4 and 20 days, respectively, with native sludge — in 35 days.

Transformation of Cr under sintering of Ca-rich solid waste with kaolin: Analysis of multi-element coupled interactions

The high toxicity of Cr–Ca compounds generated during the heat treatment of solid waste will heavily threat the environment. In this work, a kind of Ca-rich river sludge which is bound with Ca and heavy metals was combusted with kaolin under 900 °C for 3 h in a muffle to study the transformation of Cr. The effects of kaolin on Cr transformation were investigated through sequential extraction, the risk assessment of heavy metals, and constant pH leaching test, also combined with crystal phase analysis of Ca–Al–Si minerals. The experimental results showed that the formation of Ca10(SiO4)3(SO4)3Cl2 was inhibited by the addition of 10% (mass fraction) kaolin and the released Cl promoted the evaporation of target elements in priority while 30% kaolin addition further inhibited the solidification of Cr. Furthermore, the effect of NaCl and CaCO3 on the Cr solidification by kaolin were also explored by leaching procedure or XRD analysis of calcination products of their mixtures. It should be noticed that the addition of kaolin in Cr2O3–CaCO3 mixture will directly react with CaCrO4 and fixed the generated Cr2O3 into internal layered structure, preventing its re-oxidization by the free CaO. This work aims to help illustrate the Cr transformation with existence of Ca during sintering of Ca-rich solid wastes and reduce the Cr contamination in future.

EVALUATING THE ANTHROPOGENIC IMPACT ON THE PRUT RIVER NEAR YAREMCHE-TOWN ON THE POLLUTION LEVEL INDICES OF BOTTOM SEDIMENTS

Introduction. One of the most objective and reliable indicators of the state of pollution of the aquatic environment and the overall level of technological load on it is the content of pollutants in bottom sediments (BS). There are no large industrial enterprises in and around Yaremche-town (Ivano-Frankivsk region), so there are no significant discharges of toxic substances into the sewage system, especially directly into the river. However, every year in this picturesque cornerof Prykarpattia the number of sanatoriums, recreation centres, cottage towns and just residential buildings grows. Accord-ingly, the Prut River, which is the pearl of this region, quite often gets untreated runoff, which pollutes not only water but also settles on bottom sediments.The purpose of this study was to assess the anthropogenic load on the Prut River based on a comprehensive environmental analysis of the state of pollution of the bottom sediments of this river upstream and downstream from Yaremche.Methods. Water extracts from bottom sediments were prepared by the recommendations of the relevant regula-tions in the ratio "bottom sediments - water" as 1: 5 in terms of the dry mass of bottom sediments. Laboratory study of hydrochemical parameters of selected samples was performed by gravimetric, titrimetric, photometric and other methods of analysis.Research results. The accumulation of ammonium salts, nitrites and nitrates, which are easily soluble, in the far above the discharge site of wastewater, is obviously due to the significant sorption properties of river sludge, which prevents these ions from being washed away by the flow. At the point of discharge of wastewater from the city, the content of these ions increases and reaches a maximum at point 3 - at a distance of approx. 100 m below the discharge site. Further downstream, their number systematically decreases. A similar distribution of concentrations is observed in the case of phosphates. Their source of getting into the river also, for the most part, belongs to the housing and communal services. A significant contribution to the increased phosphate content in the sample below the discharge is made by urban wastewater, in which even after treatment the concentration of phosphate ions remains quite high. The fact of the presence of oil products in the bottom sediments at the investigated area was revealed. The constant increase in the number of road transport on the banks of this resort river inevitably leads to the ingress of products of incomplete combustion of fuel, uncontrolled spills.Conclusions. Upstream from the place of discharge into the Prut River of treated wastewater in the city of Yaremche, the concentrations of salts-pollutants of the biogenic group are formed due to uncontrolled sources of domestic sew-age. In this area, the pollution of bottom sediments is insignificant, slightly higher at the discharge site, and they are of the greatest importance below the discharge. This fact indicates the growing anthropogenic impact of coastal cities on the state of the river and in general, and pollution of bottom sediments, in particular. For the first time oil products were found in bottom sediments in the studied area. The reason for this phenomenon is the constant increase in the number of vehicles on the banks of this river.

Assessment of magnesium potassium phosphate cement for waste sludge solidification: Macro- and micro-analysis

The feasibility and performance of eco-friendly and sustainable magnesium potassium phosphate cement (MKPC) to solidify urban river sludge are innovatively evaluated. To probe exhaustively into the mechanical performance and micromechanism of MKPC solidified dredged sludge, the effect of binder content, Mg/P molar ratio, retarder (borax) content and curing age are analyzed through unconfined compressive strength (UCS), mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests. The experimental findings indicate the compressive strength is raised owing to an increase in MKPC amount and curing age. The isolation effect of sludge matrix weakens the retarding effect of borax, but reasonable borax content is beneficial to the strength improvement at longer curing age. The UCS of solidified samples with lower molar ratio (Mg/P = 3) increases rapidly at the early age while limitedly in later stage. The UCS reaches the maximum at the molar ratio of Mg/P = 4–5. The XRD and MIP analysis demonstrates that MgKPO4·6H2O (struvite-k) is the major hydration phase produced along with unreacted dead burned magnesia. Struvite-k can effectively fill the large pores (1–10 μm) and cause the transformation of large pores into small pores (0–0.1 μm), which has a good refinement performance for pore structure. The SEM images show that the prismatic or layered struvite-k forms preferentially and its final morphology is intimately connected with the Mg/P molar ratio. When the MKPC dosage and curing age increase, the struvite-k crystals are significantly densified and some microcracks appear due to the surface tension effect during the hydration heat-associated dehydration in crystal growth process. The synthesized crystal is fully developed and the crystal grows more completely under appropriate reaction conditions and reasonable relative concentration of reactants, which produces stronger interconnection between sludge particles and denser microstructure within matrix, contributing to the strength development of solidified sludge. In summary, the mechanical, eco-friendly and cost-efficient benefits could be highly anticipated from substituting MKPC for Portland cement (PC) in sludge solidification.

Strength, durability and microstructure of granulated blast furnace slag-modified magnesium oxychloride cement solidified waste sludge

Due to huge carbon emissions associated with the production of Portland cement (PC), the pursuit of sustainable and efficient cementitious materials is a major challenge to manage solid wastes including urban river sludge. As an eco-friendly alternative to PC, granulated blast furnace slag (GBFS)-modified magnesium oxychloride cement (MOC) is innovatively introduced in sludge solidification. The slag modification to MOC and their synergistic efficiency on sludge treatment is systematically evaluated by unconfined compressive strength (UCS), durability and microstructural tests, considering slag dosage, molar ratio of MgO/MgCl 2 and curing age. The obtained results suggest that MOC-slag mixture is efficient in sludge solidification and the inclusion of slag overcomes the strength retraction of MOC solidified sludge. The mechanical behaviour is closely concerned with the formation of phase 5, brucite and C–S–H gels, which imposes a dominant impact on the morphology and microstructure of solidified sludge. Especially, the physic-chemical effect of slag is able to improve the durability of MOC solidified sludge, and induces an enhancement of its long-term stability. The C–S–H gels formed by alkaline activation of slag are the crucial cause of improvement in long-term strength and durability of MOC-slag solidified sludge. In brief, the combined agent of slag-modified MOC shall be deemed as an effective and eco-friendly approach for urban sludge disposal. • Magnesium oxychloride cement is innovatively introduced to dispose of waste sludge. • Slag overcomes strength retraction and improves durability of MOC solidified sludge. • Strength is highly dependent on MgO/MgCl 2 molar ratio, slag dosage and curing time. • MOC-slag system governs strength, durability and microstructure of solidified sludge. • Phase 5, C–S–H and brucite are detected as mechanisms of MOC-slag solidified sludge.

Time-delayed photocatalysis enhanced microbial nitrate reduction via solar energy storage in carbon nitrides

The increase in nitrogen, especially nitrate, in the water environment poses a great threat to human health and makes the need to develop ways to efficiently remove nitrate from water. Here, we established a novel time-delayed denitrification system for the first time using dark photocatalyst, the cyanamide-functionalized heptazine-based polymer (NCN-CNx). Interestingly, the dark photocatalysis system can store electrons when being irradiated, and release them as needed when being coupled with a conductive co-catalyst in dark environment. The changes in concentration of nitrate, nitrite and ammonia were measured to state the improved denitrification performance, and the enzyme activities and electrochemical behaviors were investigated to explore the mechanism of the denitrification system. The results showed that NCN-CNx had a positive effect on the microbial nitrate removal process because of the release of stored photogenerated electrons. Electrons released by a co-catalyst (graphene) on demand could promote microbial denitrification with a 77% nitrate removal efficiency, which was almost 4.8 times and 3.1 times higher than that of the photocatalytic group and the microbial group. Correlation analysis indicated that the activities of nitrate reductase, nitrite reductase, and catalase as well as electron transport system were the most important relative factors affected by NCN-CNx during the denitrification process. Furthermore, bacterial community analysis revealed that NCN-CNx increased the relative abundance of denitrifiers, including Sphingomonadaceae, Xanthomonadaceae and Cyclobacteriaceae, in the treated communities compared with the original community in river sludge. These findings provided some new insights into the mechanism by which dark photocatalyst can enhance the denitrification process and the establishment of day/night photocatalytic systems for sustainable removal of nitrate in water.

Puesta a punto de dispositivos para ensayos de digestión anaeróbica

La Digestión Anaeróbica (DA) permite tratar residuos orgánicos y transformarlos en productos con valor agregado: el biogás y el digerido. En el presente trabajo se confeccionaron y testearon dispositivos para ensayos de DA en modalidad discontinua de 530 ml (Dispositivo tipo 1) y semi-continua de 5.62 L (Dispositivo tipo 2). El Dispositivo 1 logró validarse por medio de ensayos con orujo de manzana, realizados por triplicado, con una producción de biogás de 142 ± 6.6 ml y de CH4 de 102.7 ± 9.8 ml y se corroboró que el agregado de cáscara de huevo mejora en un 43.06% la generación de CH4. Otro estudio, realizado con orujo de manzana y macroalgas en distintas proporciones, mostró los valores más altos de CH4 para la DA con 100% orujo (224.33 ± 21.59 ml), seguido por 50-50% orujo-macroalgas (92.5 ± 14.73 ml) y por último, 100% macroalgas (6.17 ± 2.93 ml). En el Dispositivo tipo 2 se realizaron pruebas de generación de inóculo a partir de lodo anaeróbico de río, y estudios con orujo de manzana y purín de cerdo, que permitieron testear la aptitud del diseño y sugerir mejoras.

Recycling of waste river sludge into unfired green bricks stabilized by a combination of phosphogypsum, slag, and cement

The current study is taken an attempt to reuse the waste river sludge (WRS) with high moisture content in the production of cost-effective unfired green bricks. For this purpose, hemihydrate phosphogypsum (HPG) was innovatively applied to dehydrate WRS, and different consecutive dosages of Ordinary Portland cement (OPC), sodium metasilicate (SMS) and pozzolanic waste materials like ground granulated blast-furnace slag were mixed with WRS. The observed results indicated the excellent performance of unconfined compressive strength (UCS) of the brick specimens that was obtained around 31 MPa employing the combinations 6: 4 of WRS and HPG along with the 16% slag and 4% OPC. Water absorption resisting capacity and UCS of this hard mixture satisfied the requirements of the Chinese standard. Moreover, the scanning electron microscopic (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) corroborated the strength development properties of bricks through progressing the microstructures along with calcium silicate hydrate (CSH) and ettringite minerals formations. The result of this study indicated that the unfired green bricks comprising the mixtures mentioned above are economical viable. Furthermore, the utilization rate of waste materials in the optimal ratio can reach 96%. Therefore, the outcomes of this research might be a potential application in the field of sludge treatment for manufacturing the cos-effective green bricks.

NEW OPPORTUNITIES OF NUCLEAR PHYSICS RESEARCH OF THE OBJECTS OF ENVIRONMENT IN THE COURT EXPERTISE ACTIVITY

In this paper are studied the possibility of using nuclear techniques, in particular, low-background measurements of the radionuclide content of natural (isotopes of natural series U / Th, 40K) and man-made origin for the identification of natural objects as non-nuclear materials. In particular, this can be the samples of soil, river sludge or rock, presented as evidential objects for court expertise. Тhe proposed technique explores new data on the nature of the nucleosynthesis of the Earth’s crust, the distribution and conditions of radioactive equilibrium of the daughter’s isotopes of the U / Th series. Recent studies show the ability to use lowbackground research data to establish standards for the content / ratio of the clarks of chemical elements U / Th / K, which may be sufficient identification signs of a given territory like fingerprints for a person. This is especially relating to such objects of the environment as samples of soils, rocks, etc. that are genetically related to a given territory. Considering these environmental objects as a subject of court examination, we can talk about their important role as an evidence-based argument, which in many cases allows us to identify the origin of the “criminal element”. Therefore, the methods of identification of environmental objects and their binding to a certain territory are very important. The paper presents the first examples of such studies on samples of soil, river sludge and rock, taken from protected areas of Transcarpathia, the influence of manmade factors on which is minimal. It justifies the choice of the minimum number of radionuclide tags of a given territory, the method of sampling to obtain the radiation characteristics of a given area, and the statistical stability of the obtained data on the content of the studied radionuclides for different series of obtained samples is investigated. Systematic studies of this kind make it possible to carry out radiation mapping of territories as the development of the ideas of Vernadsky about the importance of taking into account ground-based radiation and to get a more accurate binding of the objects under study to a specific region. The possibility of using the nuclear dating technique in forensic analysis according to low-background measurements about the content of natural U / Th series in environmental objects is shown. The results of nuclear dating of samples of the Carpathian rocks using the uranium method are presented. Summing up, it can be said that nuclear techniques can be used not only to analyze radioactive materials, but also to complement effectively traditional physicochemical studies of the non-nuclear materials as forensic objects.

Strength properties and associated mechanisms of magnesium oxychloride cement-solidified urban river sludge

Eco-friendly magnesium oxychloride cement (MOC) is incorporated to reduce the disposal obstacles and mitigate the environmental impacts related to the urban river sludge. Three major factors including MOC content, molar ratio of MgO/MgCl2 and curing time are examined by unconfined compressive strength (UCS) tests. The microscopic effect caused by the MOC-hydration process is identified using X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) technique to reveal the intrinsic mechanisms. The results show that MOC content, molar ratio of MgO/MgCl2 and curing time strongly affects the UCS of MOC-solidified sludge. The suitable parameter values for sludge treatment by MOC turn out to be molar ratio of MgO/MgCl2 of 8–10, MOC content of 10% and curing time of 60 d. The UCS and strength retention coefficient of MOC-solidified sludge present an important decreasing trend with water immersion time due to the gradual decomposition of phase 5 – 5 Mg(OH)2·MgCl2·8H2O into Mg(OH)2 phase, some soluble ions and H2O molecules. The UCS development is directly related to the formation of phase 5 and brucite, which induces a transformation of pore structure and boosts to develop a much stronger interlocking microstructure in solidified matrix. The identification of brucite with a significant volumetric expansion and phase 5 provides an insightful interpretation for the strength evolution of MOC-solidified sludge. Overall, the innovative incorporation of MOC treatment is supposed to be an efficient and sustainable approach on sludge solidification.

Biodegradation of typical BFRs 2,4,6-tribromophenol by an indigenous strain Bacillus sp. GZT isolated from e-waste dismantling area through functional heterologous expression

Legacy wastewater contaminants from e-waste dismantling process such as 2,4,6-tribromophenol (TBP), one of the most widely used brominated flame retardants (BFRs), have raised concern owing to their toxicity and recalcitrance. Our previously isolated Bacillus sp. GZT from river sludge in e-waste dismantling area is a good candidate for bioremediation of BFRs contaminated sites considering its remarkable degradability of TBP and its intermediates. However, there exists a new challenge because bio-degrader cannot produce enough biomass or metabolic activity to cleanup TBP in practice complex environment. Here, we heterologously expressed and functionally characterized the genes and enzymes responsible for TBP degradation to examine the feasibility of enhancing the ability of this microorganism to detoxify TBP. Results demonstrated that five recombinant strains containing functional genes, designated tbpA, tbpB, tbpC, tbpD, and tbpE, become more tolerant toward a wide range of brominated compounds than the nontransgenic strain. Cytochrome P450 reductase encoded by tbpA gene could greatly increase efficiency to remove TBP (98.8%), as compared to wild-type strain GZT (93.2%). Its debromination intermediates 2,4-dibromophenol, 2,6-dibromo-4-methylphenol and 2-bromophenol were significantly metabolized by halophenol dehalogenases encoded by tbpB, tbpC, and tbpD, respectively. Finally, under the function of tbpE gene encoding enzyme, further debrominated product (phenol) was dramatically detoxified. To reduce the risk of these xenobiotics, the expression of these genes can be induced and significantly up-regulated during exposure to them. These results open broad scope for future study in developing genetic engineering technologies for more efficient remediation wastewater of e-waste recycling sites contaminated with TBP, which would certainly be important steps to lower TBP exposures and prevent potential health effects.

Biodegradation of di-(2-ethylhexyl) phthalate by a newly isolated Gordonia sp. and its application in the remediation of contaminated soils

A bacterial strain (Gordonia sp. Lff) capable of efficiently degrading di-(2-ethylhexyl) phthalate (DEHP) was isolated from river sludge. The optimal pH and temperature for the degradation of DEHP by Lff were 7.0 and 35 °C, respectively. Lff could degrade high concentrations of DEHP (100–2000 mg/L) with a degradation efficiency of over 91.43%. The DEHP degradation curves fit well with first-order kinetics, with a half-life ranging from 0.598 to 0.746 d. Substrate inhibition analyses showed that the maximum specific degradation rate, half-saturation constant and inhibition constant were 0.8 d−1, 45.8 mg/L and 462.18 mg/L, respectively. A detailed biodegradation pathway of DEHP was proposed based on GC–MS analysis. Furthermore, Lff could also efficiently degrade DEHP in soils. DEHP or DEHP plus Lff changed the bacterial community in soils, and Lff accelerated the shaping of the bacterial community. To the best of our knowledge, this study is the first to perform a detailed investigation into the biodegradation of DEHP in soil by Gordonia sp. and its effect on the soil bacterial community. These results suggest that Lff is an ideal candidate for the bioremediation of DEHP-contaminated environments.

Performance of sequencing batch reactor (SBR) of treated tofu wastewater: variation of contact time and activated sludge sources

One of the wastewater treatment system that is able to reduce levels of contamination are industrial wastewater using Sequencing Batch Reactor (SBR). Important in the early stages of SBR is filling phase (filling) consisting of seeding and acclimatization period. In the seeding and acclimatization period, the reactor will be filled with activated sludge and wastewater aeration process during the next study period. This research was conducted to find out sources and the best contact time of the activated sludge in lowering the concentration of COD and TSS from wastewater of tofu industry. Activated sludge which will be used is sourced from slaughter house, gutters of tofu industry, and polluted rivers. The variation of contact time which will be used is day 0; 1; 3; 5; 9 and 13. The results showed that the activated sludge are sourced from a polluted river sludge with the best percent COD reduction of 81% and TSS by 94% at day 13.