Search Results (11)

Preventing the rebound of black and odorous water bodies is critical for improving the ecological environment of water bodies. This study examined the effect and underlying mechanism of in-situ improvement of the sediment microenvironment by nitrate in the tailwater of wastewater treatment plants combined with aerobic denitrifying bacteria under low-DO regulation (TailN + CFM + LDO). On the 60th day of remediation, the levels of dissolved oxygen and oxidation–reduction potential in the overlying water rose to 5.6 mg/L and 300 mV, respectively, the concentration of acid volatile sulfide within the sediment significantly decreased by 70.4%, and the organic matter content in the sediment was reduced by 62.7%, in which the heavy fraction organic matter was degraded from 105 g/kg to 56 g/kg, and the potential risk of water reverting to black and odorous conditions significantly decreased. Amplicon sequencing analysis revealed that the relative abundance of the electroactive bacteria Thiobacillus and Pseudomonas with denitrification capacity was found to be significantly higher in the TailN + CFM + LDO group than in the other remediation groups. Functional prediction of the 16S sequencing results indicated that both the quantity and activity of critical microbial enzymes involved in nitrification and denitrification processes could be enhanced in the TailN + CFM + LDO group. These results improved our understanding of the improvement of the sediment microenvironment and could thus facilitate its application. Full article

Black-odor water is prevalent in southeastern coastal regions of China, compromising both the aquatic ecosystem and urban aesthetics. Micro- and nano-bubbles (MNBs) aeration, identified as an innovative approach, offers potential improvements in water ecological function. This study introduces and implements an MNBs technique to rehabilitate an urban black-odor river. Results indicate that MNBs aeration achieved a significantly higher increment rate of dissolved oxygen (89.4%) and higher removal efficiencies of biological oxygen demand (54.4%), chemical oxygen demand (39.0%), ammonia nitrogen (63.2%), total phosphorus (28.0%) and dimethyl trisulfide (100%) in the water compared to conventional blast aeration. Concurrently, a 25.0% increase in the ratio of iron/aluminum-bonded phosphorus (Fe/Al-P) to total sediment phosphorus effectively curtailed endogenous phosphorus release. Additionally, MNBs aeration markedly reduced plankton biomass, suggesting direct removal by MNBs. This enhanced performance is attributable to the improved oxygen mass transfer coefficient and oxygenation capacity, fostering more efficient pollutants. Furthermore, MNBs significantly encouraged the growth of aerobic microorganisms (e.g., Actinobacteria, Firmicutes and Myxococcota) in the sediment, bolstering the water’s self-purification ability. Consequently, this study validates MNBs as a highly promising solution for treating black odorous water bodies. Full article

Black-odorous water bodies in the Pearl River Delta have been treated. However, the re-release of nitrogen (N)-containing compounds in sediment can cause a relapse of black-odorous water bodies. Sediment–water ratio (SWR) and hydraulic residence time (HRT) influence pollutant release. Therefore, how to control SWR and HRT during the treatment process has become an urgent problem. This study focuses on the dynamic release of endogenous inorganic N from sediments into overlying water in a river channel of Dongguan City, Guangdong Province. Physicochemical parameters (dissolved inorganic nitrogen (DIN), NH₄⁺-N, NO₃⁻-N, NO₂⁻-N, dissolved oxygen (DO), pH, oxidation-reduction potential (ORP), chemical oxygen demand (COD), Fe and total phosphorus (TP)) of overlying water were monitored under different SWRs (0.71, 0.38, and 0.16) and HRTs (13 days and 6.5 days), and the nitrogen release flux under different conditions was compared. Finally, the correlation and influence pathways among environmental factors were analyzed. The results showed that SWR significantly affected DO, pH, ORP, and sediment N release fluxes while prolonging HRT-promoted denitrification. DIN → NO₂⁻-N → DO pathway had a total effect of 19.6%, and DIN may promote low DO concentration via NO₂⁻ oxidation. Maintaining reasonable SWR and HRT can reduce the release of inorganic N from sediment into the overlying water. This study provides a theoretical basis for controlling black-odorous water bodies. Full article

The extremely serious urban runoff eutrophication and black odorous phenomenon pose a significant threat to the lake aquatic ecosystem, resulting in a significantly increased frequency, magnitude, and duration of algal blooms in lakes. However, few investigations focus on small tributaries of the lakes, despite the ubiquity and potential local importance of these runoffs. Thus, the labile sediments NH₄⁺-N, NO₃⁻-N, PO₄³⁻, Fe²⁺, and S²⁻ in black odorous runoff at Wuxi were overall analyzed at high resolution using diffusive gradients in thin films (DGT). The variations in labile N, P, Fe, and S distribution profiles at different sampling sites indicated high heterogeneity in sediments. The concentrations of labile P, Fe, and S showed synchronous variation from the sediment-water interface (SWI) up to −20 mm along sediment profiles. Moreover, there existed a significant positive correlation among labile P, Fe, and S concentrations (p < 0.05), which might represent typical odor compounds’ FeS and H₂S synchronous release process in urban runoff. Furthermore, the apparent diffusion fluxes of labile P, Fe, and S across the SWI were all released upward, while fluxes of NH₄⁺-N and NO₃⁻-N release downward, indicating the sediments act as source and sink of P and N, respectively. Sediments’ potential for endogenous P and N fractions release results in the black−odorous water, and sediment finally abouchement the Taihu, which intensifies further lake eutrophication phenomenon. Full article

As an extreme phenomenon of water pollution, black odorous water not only causes ecological damage, but also severely restricts urban development. Presently, the in situ remediation technology for sediment from river channels is still undeveloped, and there are many bottlenecks in the key technologies for sediment pollution control and ecological restoration. In this study, three experimental tanks were used to explore the restoration effect of Al-modified zeolite with oxygen nanobubbles on black odorous sediment from the Shichuan River. One of the tanks housed Typha orientalis and Canna indica L. (TC), another tank housed the same plants and had Al-modified zeolite with oxygen nanobubbles (TC+AMZON), and the last tank was used as a comparison test (CS). The results show that the nitrogen (N) and phosphorus (P) in the sediment are violently released into the surrounding water. However, TC+AMZON could effectively inhibit the release of P. The released amount of soluble reactive phosphorus (SRP) from the pore water in the sediment reached its maximum at 40 d, and the amounts were 122.97% and 74.32% greater in TC and CS, respectively, than in TC+AMZON. However, the released amount of total phosphorus (TP) reached its maximum at 70 d, and the amounts were 260.14% and 218.23% greater in TC and CS, respectively, than in TC+AMZON. TC+AMZON significantly increased the dissolved oxygen (DO) and the oxidation-reduction potential (ORP) of pore water in the sediment in the early stages of the test. At 0 d, the DO content in TC+AMZON reached 10.6 mg/L, which is 112.0% and 178.95% greater than in TC and CS, respectively. The change law of ORP in the sediment is consistent with the DO. TC+AMZON significantly improved the transparency and reduced the content of chlorophyll_a in the upper water and could slightly reduce the N and P content in overlying water. The transparency of TC+AMZON increased by 130.76% and 58.73%, and chlorophyll_a decreased by 55.6% and 50.0% when compared to TC and CS, respectively. Full article

Black odorous sediment pollution in urban areas has received widespread attention, especially pollution caused by acidified volatile sulfide (AVS), phosphorus and heavy metals. In this study, an Fe₃O₄@BC composite was fabricated by the coprecipitate method of Fe₃O₄ and biochar (BC) and was mixed with calcium peroxide (CP) for sediment pollution treatment. The results showed that the AVS removal rate could reach 52.8% in the CP+Fe₃O₄@BC system and −18.1% in the control group on the 25th day. AVS was removed in the following three ways: AVS could be oxidized with oxygen produced by CP; H₂O₂ produced from CP also could be activated by Fe²⁺ to generate hydroxyl radicals that have strong oxidation properties to oxidize AVS; AVS could also be removed by bacterial denitrification. As for phosphorus, total phosphorus (TP) content in overlying water remained at 0.1 mg/L after CP and Fe₃O₄@BC were added. This is due to the conversion of NH₄Cl-P and Fe/Al-P into Ca-P in sediments, which inhibited the release of phosphorus. Simultaneously, the release and migration of heavy metal chromium (Cr) were slowed, as demonstrated by the results (the acid extractable and reducible states of Cr in the sediment decreased to 0.58% and 0.97%, respectively). In addition, the results of the high-throughput genetic test showed the total number of microorganisms greatly increased in the CP+Fe₃O₄@BC group. The abundance of Sulfurovum increased while that of sulphate-reducing bacteria (SRBs) was inhibited. Furthermore, the abundance of denitrifying bacteria (Dechlorominas, Acinetobacter and Flavobacterium) was increased. In brief, our study showed the synergistic effect of Fe₃O₄@BC composites and CP had a remarkable effect on the urban sediment treatment, which provides a new way to remove sediment pollution. Full article

In situ remediation of sediment pollution is an important measure for the treatment of urban black-odorous water. In this study, the process of calcium nitrate dosing and low oxygen aeration was used to repair the sediment of black-odorous water body in a glass container. The variation trend and removal efficiency of ammonia nitrogen and nitrate nitrogen in sediment and overlying water were investigated during the process. By establishing the double logarithm model of calcium nitrate sediment repair process, the change law of ammonia nitrogen and nitrate nitrogen content in sediment under different calcium nitrate dosing conditions was studied, and the denitrification process of different calcium nitrate dosing and low oxygen aeration was simulated. The results showed that by establishing the double logarithm model of calcium nitrate sediment remediation process, when the dosage of calcium nitrate was 6%, the inhibition rate of calcium nitrate on nitrate nitrogen release was the largest. The stable inhibitory concentration of nitrate nitrogen was 11.65 mg/g, and the stable inhibited concentration of ammonia nitrogen was 382.95 mg/kg. The stable inhibitory concentration of nitrate nitrogen and ammonia nitrogen in overlying water was 8.34 mg/L and 16.47 mg/L. Moreover, excessive calcium nitrate (8%) may increase the risk of microbial ecological environment in sediment and weaken the inhibitory effect. The optimum parameters were the calcium nitrate dosage of 6%, the reaction time of 21 days, and the aeration rate of 30 mL/min. Under these conditions, the removal effect of ammonia nitrogen in sediment and overlying water was further improved, and the concentration of nitrate nitrogen was effectively controlled. The stable inhibitory content of nitrate nitrogen in sediment was 5.55 mg/g, and the stable inhibitory content of ammonia nitrogen was 982.79 mg/kg. The stable inhibitory concentration of nitrate nitrogen and ammonia nitrogen in overlying water was 6.55 mg/L and 118.20 mg/L. Based on a simulation, this study provides important technical support for the formulation of a refined endogenous pollution control scheme by controlling the process of calcium nitrate remediation and low oxygen aeration. Full article

Rapid urbanization has destroyed urban water systems and led to blackened and odorous rivers. The heavily polluted rivers are always facing eutrophication and heavy metal pollution, while the combined effects of these environmental factors on the microbial diversity and distribution of the river microbial communities have not been adequately reported, especially the archaeal communities. In this study, we investigated the community structure and microbial distribution of sediment archaeal communities from an urban blackened and odorous river basin of the Zhang river, in Nanling, China. Results showed that the archaeal community from the eight sediment sites have average values of Shannon and Chao1 at 3.4921 and 232.7202, respectively. The community diversity and richness were different among samples. Halobacterota and Euryarchaeota were the most abundant phylum and Crenarchaeota also took up a considerable amount of the archaeal community. To reveal the main environmental drivers of the distribution of archaeal communities in sediment, the environmental physicochemical factors (total nitrogen, total phosphorus, oxidation/reduction potential, nitrate nitrogen, ammonia nitrogen, pH and total organic carbon) and heavy metals (Cr, Ni, Cu, Zn, As, Cd, Pb and Hg) in sediment were determined. A redundancy analysis (RDA) revealed that Eh was the most prominent influencing factor, and As was the most influential heavy metal on the microbial distribution of archaeal communities. Furthermore, a variance partitioning analysis (VPA) was used to identify the impacts of physicochemical factors and heavy metals on the archaeal community distribution. Results showed that heavy metals have higher effects on archaeal community distribution than physicochemical factors. The present study suggested that the heavy metal pollution should be paid more attention in the microbial distribution in heavily polluted urban rivers, and also should be taken into consideration for improving the efficacies of ecological evaluation and remediation. Full article

Reducing and remediating endogenous sediment pollution in urban rivers using appropriate microbiological remediation technology is regarded as a safe, effective, and environmentally sustainable mechanism. In this study, the pollutant removal efficiency of three microorganism types at different dosages was studied in the laboratory. To optimize the microbial restoration scheme, a comprehensive analysis of their effectiveness in removing total nitrogen (TN), total phosphorus (TP), total organic matter (OM), and polycyclic aromatic hydrocarbons (PAHs) was conducted, and associated structural changes in the sediment bacteria were analyzed. The results showed that using nitrifying bacteria and Bacillus as microbial agents resulted in superior removal efficiencies of TN and TP in sediments, whereas yeast was not as effective. The removal rates of TN reached 27.65% and 20.88% when 5 mg nitrifying bacteria and 10 mg Bacillus respectively, were used. A comparative analysis showed that nitrifying bacteria exhibited a better TN removal effect; however, Bacillus exhibited a better TP removal effect. The results of high-throughput sequencing revealed no significant changes to the microbial community structures when optimal microorganisms or beneficial microorganisms that thrive using OM as a source of C and energy were added. This study provides insights into the processes and mechanisms involved in the microorganism degradation of black and odorous sediment, and the results can be used as a basis for developing endogenous pollution control policies and methods for urban rivers. Full article

The phenomenon of black-odor urban rivers with rapid urbanization has attracted extensive attention. In this study, we investigated the water quality and composition of sediment-associated bacteria communities in three remediation stages (before remediation, 30 days after remediation, and 90 days after remediation) based on the in situ remediation using comprehensive measures (physical, chemical, and biological measures). The results show that the overlying water quality was notably improved after in situ remediation, while the diversity and richness of sediment-associated bacterial communities decreased. A growing trend of some dominant genus was observed following the remediation of a black-odor river, such as Halomonas, Pseudomonas, Decarbonamis, Leptolina, Longilina, Caldiseericum, Smithella, Mesotoga, Truepera, and Ralstonia, which play an important role in the removal of nitrogen, organic pollutants and hydrogen sulfide (H₂S) during the sediment remediation. Redundancy analysis (RDA) showed that the bacterial community succession may accelerate the transformation of organic pollutants into inorganic salts in the sediment after in situ remediation. In a word, the water quality of the black-odor river was obviously improved after in situ remediation, and the bacterial community in the sediment notably changed, which determines the nutrients environment in the sediment. Full article

Contrary to the constraints in time, investment, and management of the traditional technology for waste water treatment, this paper seeks to propose a more advanced, reliable, and affordable new technology to restore urban polluted rivers to pristine quality levels. The paper also presents new ideas on the selection and use of microbial agents to improve the efficiency of pollution removal. It presents the successful implementation of microbial technology (MT) on Chengnan River, which was heavily polluted before MT implementation. Without artificial aeration, sediment dredging, or complete sewage interception, we directly sprayed a previously configured HP-RPe-3 Microbial Agent into the water body and sediment. We considered the feasibility of MT for treating polluted urban rivers from the perspective of several water quality indices evaluation methods. After the treatment, the concentration of dissolved oxygen (DO) reached 5.0 mg/L, the removal rates of ammonia nitrogen (NH₃-N) and chemical oxygen demand (COD) reached 20% and 38% respectively, and the average degradation rate of total phosphorus (TP) along river was close to 15%. Also, the Nemerow Index of the river was reduced from 2.7 to 1.9. The Fuzzy Comprehensive Index shows a tendency for improvement from Inferior Grade V to a better grade (approximately Grade III). The color of the river water changed, from black or dark green, to its original color. The results indicate that the bioremediation technology of directly adding microbial agents mainly aimed for the degradation of NH₃-N can preliminarily eliminate the black-odor phenomenon of urban rivers, and improve their water quality. It is expected that the MT application, and the concept of how to select the corresponding microbial agents according to main pollutants, can be widely accepted and applied to similar cases. Full article