International Journal of Environmental Research and Public Health

2023

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14 pages, 4681 KiB

Open AccessArticle

Enhancing the Biological Oxidation of H₂S in a Sewer Pipe with Highly Conductive Concrete and Electricity-Producing Bacteria

by Huy Thanh Vo, Tsuyoshi Imai, Masato Fukushima, Kanathip Promnuan, Tasuma Suzuki, Hiraku Sakuma, Takashi Hitomi and Yung-Tse Hung

Int. J. Environ. Res. Public Health 2023, 20(2), 1459; https://doi.org/10.3390/ijerph20021459 - 13 Jan 2023

Cited by 1 | Viewed by 1902

Abstract

Hydrogen sulfide (H₂S) generated in sewer systems is problematic to public health and the environment, owing to its corrosive consequences, odor concerns, and poison control issues. In a previous work, conductive concrete, based on amorphous carbon with a mechanism that operates [...] Read more.

Hydrogen sulfide (H₂S) generated in sewer systems is problematic to public health and the environment, owing to its corrosive consequences, odor concerns, and poison control issues. In a previous work, conductive concrete, based on amorphous carbon with a mechanism that operates as a microbial fuel cell was investigated. The objective of the present study is to develop additional materials for highly conductive concrete, to mitigate the concentration of H₂S in sewer pipes. Adsorption experiments were conducted to elucidate the role of the H₂S reduction. Additionally, electricity-producing bacteria (EPB), isolated from a municipal wastewater treatment plant, were inoculated to improve the H₂S reduction. The experimental results showed that inoculation with EPB could decrease the concentration of H₂S, indicating that H₂S was biologically oxidized by EPB. Several types of new materials containing acetylene black, or magnetite were discovered for use as conductive concrete, and their abilities to enhance the biological oxidation of H₂S were evaluated. These conductive concretes were more effective than the commercial conductive concrete, based on amorphous carbon, in decreasing the H₂S concentration in sewer pipes. Full article

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2022

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10 pages, 1375 KiB

Open AccessArticle

Startup of Demo-Scale Anaerobic Digestion Plant Treating Food Waste Leachate: Process Instability and Recovery

by Seung Gu Shin, Su In Kim and Seokhwan Hwang

Int. J. Environ. Res. Public Health 2022, 19(11), 6903; https://doi.org/10.3390/ijerph19116903 - 5 Jun 2022

Cited by 1 | Viewed by 2094

Abstract

A demo-scale (600 m³ working volume) anaerobic digester treating food waste leachate was monitored during its startup period. The operation strategy was adjusted twice (i.e., three distinct phases) during the operation to recover the process from instability. During the first phase, the [...] Read more.

A demo-scale (600 m³ working volume) anaerobic digester treating food waste leachate was monitored during its startup period. The operation strategy was adjusted twice (i.e., three distinct phases) during the operation to recover the process from instability. During the first phase, the organic loading rate (OLR) > 2.7 kg chemical oxygen demand (COD)/m³∙day corresponded to volatile fatty acid (VFA) accumulation along with a decreasing pH, resulting in the drop in biogas yield to 0.43 ± 0.9 m³/kg COD_in. During phase 2, fast recovery of this process was aimed at using a sequencing batch operation. One batch cycle (5 to 2 days) consisted of the combined drawing and feeding step (5 h), the reacting step (91 to 17 h), and the settling step (24 h). The duration of the reacting step was determined for each cycle such that (1) the biogas production ceased before the cycle end and (2) the residual VFA concentration was < 1 g/L. In total, 11 cycles were operated with a gradual increase in biogas yield to 0.55 m³/kg COD_in with the absence of any sign of system disturbance. After phase 2, the digester was fed at the designed OLR of 4.1 ± 0.3 kg COD/m³∙day. The biogas yield was elevated to 0.58 ± 0.2 m³/kg COD_in during phase 3 with the residual VFA concentration maintained at 2.2 ± 0.6 g/L. Methanogen populations, as determined by real-time PCR, did not change significantly throughout the period. These results imply that the adaptation of this process to the OLR of ca. 4 kg COD/m³∙day was not due to the increase in methanogen population but due to the elevation of its activity. Overall, this study suggests that the sequencing batch operation with adjustable cycle duration can be one successful recovery strategy for biogas plants under system instability. Full article

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18 pages, 6106 KiB

Open AccessArticle

Application of Integrated Fixed-Film Activated Sludge in a Conventional Wastewater Treatment Plant

by Magdalena Kuśnierz, Magdalena Domańska, Kamila Hamal and Agnieszka Pera

Int. J. Environ. Res. Public Health 2022, 19(10), 5985; https://doi.org/10.3390/ijerph19105985 - 14 May 2022

Cited by 7 | Viewed by 3770

Abstract

It is often only at the operation stage of a wastewater treatment plant that there is a need to adjust the treatment process in terms of variable hydraulic capacity, increased pollutant load, high/low concentration of suspended biomass, or the unfavorable phenomenon of reduced [...] Read more.

It is often only at the operation stage of a wastewater treatment plant that there is a need to adjust the treatment process in terms of variable hydraulic capacity, increased pollutant load, high/low concentration of suspended biomass, or the unfavorable phenomenon of reduced sedimentation capacity of the activated sludge. One of the ways to improve the treatment process efficiency is to increase the biologically active surface by using bio-carriers in the form of fibers, materials, or bio-balls. This paper presents the results of a wastewater treatment plant operation during the period of six months after the implementation of the integrated fixed-film activated sludge (IFAS) technology. The research showed that microorganisms developed both in the activated sludge and on the fibers, positively influencing the activated sludge condition. During the start-up of the IFAS process, ciliates predominated over the other species. However, as oxygen content was high (2 mg/dm³ and more) and textile beds were used, the protozoan population developed intensively, and small metazoans became increasingly common. Throughout the research period, nitrifying and phosphorus-accumulating bacteria were observed both in the activated sludge and on the fibers. Between the 59th and 184th day of operation, numerous microorganisms were detected on the fibers and in the activated sludge, testifying to low biological oxygen demand, good aerobic conditions for nitrification, and long sludge age. However, the process seemed to break down after day 72, when the occurrence of metazoan led to reduced sludge production; after day 88, chemical oxygen demand and total suspended solids in the outflow increased, and oligochaetes and rotifers dominated the suspended sludge and fibers. Results also showed that the textile bed and low ammonia concentration became an excellent substrate for the development of Stentor sp. With regard to chemical and biological oxygen demand, total nitrogen- and total phosphorus-effluent concentrations were mostly within the legally permissible limits throughout the 184 days of operation. Full article

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15 pages, 4098 KiB

Open AccessArticle

Enhanced Nutrient Removal in A₂N Effluent by Reclaimed Biochar Adsorption

by Peng Chen, Junkang Wu, Yue He, Yaping Zhang, Ran Yu and Xiwu Lu

Int. J. Environ. Res. Public Health 2022, 19(7), 4016; https://doi.org/10.3390/ijerph19074016 - 28 Mar 2022

Cited by 1 | Viewed by 2408

Abstract

The excessive nitrogen and phosphorus discharged into the water environment will cause water eutrophication and thus disrupt the water ecosystem and even exert biological toxicities. In this study, the absorption removal of nitrogen and phosphorus from the anaerobic tank in an anaerobic–anoxic/nitrifying system [...] Read more.

The excessive nitrogen and phosphorus discharged into the water environment will cause water eutrophication and thus disrupt the water ecosystem and even exert biological toxicities. In this study, the absorption removal of nitrogen and phosphorus from the anaerobic tank in an anaerobic–anoxic/nitrifying system using four different kinds of biowaste-reclaimed biochars were investigated and compared. The effects of temperature and pH on nutrient adsorption removal were further investigated. The four kinds of biochar were successfully prepared and well characterized using a scanning electron microscope, fourier transform infrared spectroscopy, X-ray diffraction and Brunner−Emmet−Teller methods. Generally, there was no significant change in chemical oxygen demand (COD) and NH₄⁺-N removal efficiencies when treated by the different biochars, while the activated sludge biochar (ASB) displayed the highest total phosphorus (TP) removal efficiency. The initial TP concentrations (<40 mg/L) displayed no remarkable effects on the TP adsorption removal, while the increase of temperature generally enhanced TP and NH₄⁺-N adsorptions on the ASB. Besides, the increase of pH significantly promoted NH₄⁺-N removal but depressed TP removal. Moreover, the adsorption process of TP by the ASB complies with the secondary kinetic model, suggesting the chemical precipitation and physical electrostatic interaction mechanisms of TP adsorption removal. However, the adsorption of NH₄⁺-N conformed to the inner-particle diffusion model, indicating that the NH₄⁺-N adsorption was mainly involved with pore diffusions in the particles. Full article

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2021

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13 pages, 2553 KiB

Open AccessArticle

Fate of Functional Bacterial and Eukaryotic Community Regulated by Earthworms during Vermicomposting of Dewatered Sludge, Studies Based on the 16S rDNA and 18S rDNA Sequencing of Active Cells

by Jun Yang, Kui Huang, Lansheng Peng, Jianhui Li and Aozhan Liu

Int. J. Environ. Res. Public Health 2021, 18(18), 9713; https://doi.org/10.3390/ijerph18189713 - 15 Sep 2021

Cited by 7 | Viewed by 2134

Abstract

DNA sequencing of active cells involved in vermicomposting can clarify the roles of earthworms in regulating functional microorganisms. This study aimed to investigate the effect of earthworms on functional microbial communities in sludge by comparing biodegradation treatments with and without earthworms. PCR and [...] Read more.

DNA sequencing of active cells involved in vermicomposting can clarify the roles of earthworms in regulating functional microorganisms. This study aimed to investigate the effect of earthworms on functional microbial communities in sludge by comparing biodegradation treatments with and without earthworms. PCR and high throughput sequencing based on pretreatment of propidium monoazide (PMA) were used to detect the changes in active bacterial 16S rDNA and eukaryotic 18S rDNA during vermicomposting. The results showed that the nitrate in sludge vermicomposting and control were significantly different from day 10, with a more stable product at day 30 of vermicomposting. Compared with the control, the Shannon indexes of active bacteria and eukaryotes decreased by 1.9% and 31.1%, respectively, in sludge vermicompost. Moreover, Proteobacteria (36.2%), Actinobacteria (25.6%), and eukaryotic Cryptomycota (80.3%) were activated in the sludge vermicompost. In contrast, the control had Proteobacteria (44.8%), Bacteroidetes (14.2%), Cryptomycota (50.00%), and Arthropoda (36.59%). Network analysis showed that environmental factors had different correlations between active bacterial and eukaryotic community structures. This study suggests that earthworms can decrease the diversity of bacterial and eukaryotic communities, forming a specific-functional microbial community and thus accelerating organic matter decomposition during vermicomposting of dewatered sludge. Full article

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13 pages, 953 KiB

Open AccessArticle

Phosphorus Recovery from Sewage Sludge Using Acidithiobacilli

by Surendra K. Pradhan, Helvi Heinonen-Tanski, Anna-Maria Veijalainen, Sirpa Peräniemi and Eila Torvinen

Int. J. Environ. Res. Public Health 2021, 18(13), 7135; https://doi.org/10.3390/ijerph18137135 - 3 Jul 2021

Cited by 6 | Viewed by 2794

Abstract

Sewage sludge contains a significant amount of phosphorus (P), which could be recycled to address the global demand for this non-renewable, important plant nutrient. The P in sludge can be solubilized and recovered so that it can be recycled when needed. This study [...] Read more.

Sewage sludge contains a significant amount of phosphorus (P), which could be recycled to address the global demand for this non-renewable, important plant nutrient. The P in sludge can be solubilized and recovered so that it can be recycled when needed. This study investigated the P solubilization from sewage sludge using Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans. The experiment was conducted by mixing 10 mL of sewage sludge with 90 mL of different water/liquid medium/inoculum and incubated at 30 °C. The experiment was conducted in three semi-continuous phases by replacing 10% of the mixed incubated medium with fresh sewage sludge. In addition, 10 g/L elemental sulfur (S) was supplemented into the medium in the third phase. The pH of the A. thiooxidans and A. ferrooxidans treated sludge solutions was between 2.2 and 6.3 until day 42. In phase 3, after supplementing with S, the pH of A. thiooxidans treated sludge was reduced to 0.9, which solubilized and extracted 92% of P. We found that acidithiobacilli supplemented with S can be used to treat sludge, i.e., achieve hygienization, removal of heavy metals, and solubilization and recovery of P. Full article

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12 pages, 2548 KiB

Open AccessArticle

Pilot-Scale Airlift Bioreactor with Function-Enhanced Microbes for the Reduction of Refinery Excess Sludge

by Hongyan Mu, Min Zhang, Shanshan Sun, Zhaozheng Song, Yijing Luo, Zhongzhi Zhang and Qingzhe Jiang

Int. J. Environ. Res. Public Health 2021, 18(13), 6742; https://doi.org/10.3390/ijerph18136742 - 23 Jun 2021

Cited by 1 | Viewed by 2222

Abstract

A pilot-scale airlift bioreactor (ALBR) system was built and operated continuously for refinery excess sludge (RES) reduction. Combined ALBR and function-enhanced microbes (composed of photosynthetic bacteria and yeast) were integrated into the system. The pilot-scale ALBR was operated for 62 days, and the [...] Read more.

A pilot-scale airlift bioreactor (ALBR) system was built and operated continuously for refinery excess sludge (RES) reduction. Combined ALBR and function-enhanced microbes (composed of photosynthetic bacteria and yeast) were integrated into the system. The pilot-scale ALBR was operated for 62 days, and the start-up time was 7 d. Continuous operation showed that the sludge reduction efficiency was more than 56.22%, and the water quality of the effluent was satisfactory. This study focused on investigating the effects of hydraulic retention time (HRT) on the stability of the system and the effect of sludge reduction. Under different HRT conditions of 40, 26.7, 20, and 16 h, the sludge reduction rates reached 56.22%, 73.24%, 74.09%, and 69.64%, respectively. The removal rates of chemical oxygen demand (COD) and total nitrogen (TN) decreased with decreasing HRT, whereas the removal rate of NH₄⁺-N increased. The removal rate of total phosphorus (TP) was approximately 30%. Results indicate that the ALBR and function-enhanced microbe system can reduce sludge and treat sewage simultaneously, and the effluent is up to the national emission standard. Addition of function-enhanced microbes can promote the degradation of petroleum hydrocarbon substances in the sludge, especially alkanes with low carbon numbers. This study suggests that the optimal HRT for the system is 16 h. The total operation cost of the ALBR combined with the function-enhanced microbe system can be reduced by 50% compared with the cost of direct treatment of the RES system. Full article

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2020

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13 pages, 2262 KiB

Open AccessArticle

Optimized Pretreatment of Non-Thermal Plasma for Advanced Sewage Oxidation

by Hee-Jun Kim, Chan-Hee Won and Hyun-Woo Kim

Int. J. Environ. Res. Public Health 2020, 17(20), 7694; https://doi.org/10.3390/ijerph17207694 - 21 Oct 2020

Cited by 8 | Viewed by 3050

Abstract

This study investigates how the non-thermal plasma (NTP) process leads to advanced oxidation of sewage using response surface methodology. For environmentally viable and efficient operation of the NTP process, temperature and contact time were selected as two important independent variables. Their impacts on [...] Read more.

This study investigates how the non-thermal plasma (NTP) process leads to advanced oxidation of sewage using response surface methodology. For environmentally viable and efficient operation of the NTP process, temperature and contact time were selected as two important independent variables. Their impacts on the performance were tested following an experimental design to figure out optimal operating conditions. Based on obtained treatment efficiency, statistically optimized conditions were derived by using an approach adapting the central composite design. Results show that coupling 40 °C of temperature and 4 h of contact time demonstrate optimal performance for total chemical oxygen demand (TCOD, 59%) and total suspended solids (85%), respectively. This implies that NTP may present efficient particulate destruction leading to organic solids dissolution. Statistical analysis reveals that the contact time shows more significant dependency than the temperature on the advanced oxidation of TCOD, possibly due to dissolved organic material. For total nitrogen removal, on the contrary, the optimal efficiency was strongly related to the higher temperature (~68 °C). This work provides an inroad to considering how NTP can optimally contribute to better oxidation of multiple pollutants. Full article

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12 pages, 2201 KiB

Open AccessArticle

Performance and Biomass Characteristics of SBRs Treating High-Salinity Wastewater at Presence of Anionic Surfactants

by Huiru Li, Shaohua Wu and Chunping Yang

Int. J. Environ. Res. Public Health 2020, 17(8), 2689; https://doi.org/10.3390/ijerph17082689 - 14 Apr 2020

Cited by 11 | Viewed by 3178

Abstract

Sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), as two anionic surfactants, have diffused into environments such as surface water and ground water due to extensive and improper use. The effects on the removal performance and microbial community of sequencing batch reactors [...] Read more.

Sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), as two anionic surfactants, have diffused into environments such as surface water and ground water due to extensive and improper use. The effects on the removal performance and microbial community of sequencing batch reactors (SBRs) need to be investigated in the treatment of saline wastewater containing 20 g/L NaCl. The presence of SDS and SDBS could decrease the removal efficiencies of ammonia nitrogen and total phosphorus, and the effect of SDS was more significant. The effect of surfactants on the removal mainly occurred during the aeration phase. Adding SDS and SDBS can reduce the content of extracellular polymeric substances (EPS). In addition, SDS and SDBS also can reduce the inhibition of high salinity on sludge activity. A total of 16 s of rRNA sequencing analysis showed that the addition of surfactants reduced the diversity of microbial communities; besides, the relative abundance value of the dominant population Proteobacteria increased from 91.66% to 97.12% and 93.48% when SDS and SDBS were added into the system, respectively. Full article

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15 pages, 5511 KiB

Open AccessArticle

Short- and Long-Term Structural Characterization of Cured-in-Place Pipe Liner with Reinforced Glass Fiber Material

by Hyon Wook Ji, Dan Daehyun Koo and Jeong-Hee Kang

Int. J. Environ. Res. Public Health 2020, 17(6), 2073; https://doi.org/10.3390/ijerph17062073 - 20 Mar 2020

Cited by 14 | Viewed by 4268

Abstract

Cured-in-place pipe (CIPP), as a kind of trenchless sewer rehabilitation technology, is a method to repair sewer pipe using unsaturated polyester resin. This study develops a CIPP liner using hot water or steam curing as well as glass fiber, in contrast to traditional [...] Read more.

Cured-in-place pipe (CIPP), as a kind of trenchless sewer rehabilitation technology, is a method to repair sewer pipe using unsaturated polyester resin. This study develops a CIPP liner using hot water or steam curing as well as glass fiber, in contrast to traditional methods, which use nonwoven fabric. Composite material samples were fabricated by combining liner materials using various methods, and the structural characteristics of the liners were compared and analyzed through short- and long-term flexural strength tests. A long-term test was conducted for 10,000 h, and the results revealed 13.3 times higher flexural strength and 8 times higher flexural modulus than the American Society for Testing Materials minimum criteria for CIPP short-term properties. The maximum creep retention factor was 0.64, thereby reducing the design thickness of the CIPP by up to 54%. The structural characteristics also improved when glass fibers were mixed with traditional CIPP liner, making it possible to reduce the thickness by 30%. Glass fibers result in high structural strength when combined with unsaturated polyester resin. Structural strength increased, even when glass fibers were mixed with traditional CIPP liner. The main contribution of this research is the development of a high strength CIPP liner and improvement of the structural properties of CIPP lining without using the specially formulated resin or lining materials. Full article

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12 pages, 1628 KiB

Open AccessArticle

Quality of Vermicompost and Microbial Community Diversity Affected by the Contrasting Temperature during Vermicomposting of Dewatered Sludge

by Hongwei Zhang, Jianhui Li, Yingying Zhang and Kui Huang

Int. J. Environ. Res. Public Health 2020, 17(5), 1748; https://doi.org/10.3390/ijerph17051748 - 7 Mar 2020

Cited by 25 | Viewed by 4227

Abstract

This study aimed to investigate the effects of temperature on the quality of vermicompost and microbial profiles of dewatered sludge during vermicomposting. To do this, fresh sludge was separately vermicomposted with the earthworm Eisenia fetida under different temperature regimes, specifically, 15 °C, 20 [...] Read more.

This study aimed to investigate the effects of temperature on the quality of vermicompost and microbial profiles of dewatered sludge during vermicomposting. To do this, fresh sludge was separately vermicomposted with the earthworm Eisenia fetida under different temperature regimes, specifically, 15 °C, 20 °C, and 25 °C. The results showed that the growth rate of earthworms increased with temperature. Moreover, the lowest organic matter content along with the highest electrical conductivity, ammonia, and nitrate content in sludge were recorded for 25 °C indicating that increasing temperature significantly accelerated decomposition, mineralization, and nitrification. In addition, higher temperature significantly enhanced microbial activity in the first 30 days of vermicomposting, also exhibiting the fastest stabilization at 25 °C. High throughput sequencing results further revealed that the alpha diversity of the bacterial community was enhanced with increasing temperature resulting in distinct bacterial genera in each vermicompost. This study suggests that quality of vermicompost and dominant bacterial community are strongly influenced by the contrasting temperature during vermicomposting of sludge, with the optimal performance at 25 °C. Full article

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2019

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15 pages, 2595 KiB

Open AccessArticle

Evolution of Antibiotic Resistance and the Relationship between the Antibiotic Resistance Genes and Microbial Compositions under Long-Term Exposure to Tetracycline and Sulfamethoxazole

by Bingbing Du, Qingxiang Yang, Ruifei Wang, Ruimin Wang, Qiang Wang and Yuan Xin

Int. J. Environ. Res. Public Health 2019, 16(23), 4681; https://doi.org/10.3390/ijerph16234681 - 25 Nov 2019

Cited by 29 | Viewed by 4846

Abstract

The removal of antibiotics and widespread of antibiotic resistance genes (ARGs) have received continuous attention due to the possible threats to environment. However, little information is available on the evolution of antibiotic resistance and the relationship between ARGs and microbial communities under long-term [...] Read more.

The removal of antibiotics and widespread of antibiotic resistance genes (ARGs) have received continuous attention due to the possible threats to environment. However, little information is available on the evolution of antibiotic resistance and the relationship between ARGs and microbial communities under long-term exposure to sub-inhibitory concentrations of antibiotics. In our study, two laboratory-scale anoxic-aerobic wastewater treatment systems were established and operated for 420 days to investigate the evolution of antibiotic resistance under exposure of 5 mg·L⁻¹ tetracycline (TC) or 5 mg·L⁻¹ TC and 1 mg·L⁻¹ sulfamethoxazole (SMX). The average removal rates of TC and SMX were about 59% and 72%, respectively. The abundance of the main ARGs responsible for resistance to TC and SMX increased obviously after antibiotics addition, especially when TC and SMX in combination (increased 3.20-fold). The tetC and sul1 genes were the predominant genes in the development of TC and SMX resistance, in which gene sul1 had the highest abundance among all the detected ARGs. Network analysis revealed that under antibiotic pressure, the core bacterial groups carrying multiple ARGs formed and concentrated in about 20 genera such as Dechloromonas, Candidatus Accumulibacter, Aeromonas, Rubrivivax, in which intI1 played important roles in transferring various ARGs except sul3. Full article

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13 pages, 2038 KiB

Open AccessArticle

Removal of Tetracycline by Hydrous Ferric Oxide: Adsorption Kinetics, Isotherms, and Mechanism

by Ji Zang, Tiantian Wu, Huihui Song, Nan Zhou, Shisuo Fan, Zhengxin Xie and Jun Tang

Int. J. Environ. Res. Public Health 2019, 16(22), 4580; https://doi.org/10.3390/ijerph16224580 - 19 Nov 2019

Cited by 35 | Viewed by 4743

Abstract

The removal of tetracycline (TC) from solution is an important environmental issue. Here we prepared an adsorbent hydrous ferric oxide (HFO) by adjusting a FeCl₃·6H₂O solution to neutral pH. HFO was characterized by a surface area analyzer, X-ray diffraction [...] Read more.

The removal of tetracycline (TC) from solution is an important environmental issue. Here we prepared an adsorbent hydrous ferric oxide (HFO) by adjusting a FeCl₃·6H₂O solution to neutral pH. HFO was characterized by a surface area analyzer, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), and was used to remove TC from solution. The influence of pH, solid-to-liquid ratio, ionic type, and strength on TC removal was investigated. Adsorption kinetics and isotherms were also determined. HFO after adsorption of TC was analyzed by FTIR and XPS to investigate the adsorption mechanism. The results showed that the adsorption of TC increased from 88.3% to 95% with increasing pH (3.0–7.0) and then decreased. K⁺ ions had little effect on TC adsorption by HFO. However, Ca²⁺ and Mg²⁺ reduced the adsorption of TC on HFO. When the concentrations of Ca²⁺ and Mg²⁺ were increased, the inhibitory effect was more obvious. Pseudo-second-order kinetics and the Langmuir model fitted the adsorption process well. The maximum adsorption capacity of TC on HFO reached 99.49 mg·g⁻¹. The adsorption process was spontaneous, endothermic, and increasingly disordered. Combination analysis with FTIR and XPS showed that the mechanism between TC and HFO involved electrostatic interactions, hydrogen interactions, and complexation. Therefore, the environmental behavior of TC could be affected by HFO. Full article

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15 pages, 1453 KiB

Open AccessArticle

Physicochemical and Biological Effects on Activated Sludge Performance and Activity Recovery of Damaged Sludge by Exposure to CeO₂ Nanoparticles in Sequencing Batch Reactors

by Qian Feng, Yaqing Sun, Yang Wu, Zhaoxia Xue, Jingyang Luo, Fang Fang, Chao Li and Jiashun Cao

Int. J. Environ. Res. Public Health 2019, 16(20), 4029; https://doi.org/10.3390/ijerph16204029 - 21 Oct 2019

Cited by 8 | Viewed by 3577

Abstract

Recently, the growing release of CeO₂ nanoparticles (CeO₂ NPs) into sewage systems has attracted great concern. Several studies have extensively explored CeO₂ NPs’ potential adverse impacts on wastewater treatment plants; however, the impaired activated sludge recovery potentials have seldom been [...] Read more.

Recently, the growing release of CeO₂ nanoparticles (CeO₂ NPs) into sewage systems has attracted great concern. Several studies have extensively explored CeO₂ NPs’ potential adverse impacts on wastewater treatment plants; however, the impaired activated sludge recovery potentials have seldom been addressed to date. To explore the physicochemical and biological effects on the activated sludge performance and activity recovery of damaged sludge by exposure to CeO₂ NPs in sequencing batch reactors (SBRs), four reactors and multiple indicators including water quality, key enzymes, microbial metabolites, the microbial community structure and toxicity were used. Results showed that 10-week exposure to higher CeO₂ NP concentration (1, 10 mg/L) resulted in a sharp decrease in nitrogen and phosphorus removal efficiencies, which were consistent with the tendencies of key enzymes. Meanwhile, CeO₂ NPs at concentrations of 0.1, 1, and 10 mg/L decreased the secretion of tightly bound extracellular polymeric substances to 0.13%, 3.14%, and 28.60%, respectively, compared to the control. In addition, two-week recovery period assays revealed that the functional bacteria Proteobacteria, Nitrospirae and Planctomycetes recovered slightly at the phyla level, as analyzed through high-throughput sequencing, which was consistent with the small amount of improvement of the effluent performance of the system. This reflected the small possibility of the activity recovery of damaged sludge. Full article

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19 pages, 6843 KiB

Open AccessArticle

Investigation of a Gas Hydrate Dissociation-Energy-Based Quick-Freezing Treatment for Sludge Cell Lysis and Dewatering

by Woojeong Kim, Hyung Kae Lee and Young-Nam Kwon

Int. J. Environ. Res. Public Health 2019, 16(19), 3611; https://doi.org/10.3390/ijerph16193611 - 26 Sep 2019

Cited by 3 | Viewed by 3019

Abstract

A gas Hydrate dissociation-energy-based Quick-Freezing treatment (HbQF) was applied for sewage sludge cell rupture and dewatering. Carbon dioxide (CO₂) and water (H₂O) molecules in sewage create CO₂ gas hydrates, and subsequently the sludge rapidly freezes by releasing the [...] Read more.

A gas Hydrate dissociation-energy-based Quick-Freezing treatment (HbQF) was applied for sewage sludge cell rupture and dewatering. Carbon dioxide (CO₂) and water (H₂O) molecules in sewage create CO₂ gas hydrates, and subsequently the sludge rapidly freezes by releasing the applied pressure. Cell rupture was observed through a viability evaluation and leachate analysis. The decreased ratios of live cell to dead cells, increased osmotic pressure, and increased conductivity showed cell lysis and release of electrolytes via HbQF. The change in physicochemical properties of the samples resulting from HbQF was investigated via zeta potential measurement, rheological analysis, and particle size measurement. The HbQF treatment could not reduce the sludge water content when combined with membrane-based filtration post-treatment because of the pore blocking of fractured and lysed cells; however, it could achieve sludge microbial cell rupture, disinfection, and floc disintegration, causing enhanced reduction of water content and enhanced dewatering capability via a sedimentation post process. Furthermore, the organic-rich materials released by the cell rupture, investigated via the analysis of protein, polysaccharide, total organic carbon, and total nitrogen, may be returned to a biological treatment system or (an) aerobic digester to increase treatment efficiency. Full article

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12 pages, 1743 KiB

Open AccessArticle

Influence of Carrier Filling Ratio on the Advanced Nitrogen Removal from Wastewater Treatment Plant Effluent by Denitrifying MBBR

by Yuanzhe Zhao, Quan Yuan, Zan He, Haiyan Wang, Guokai Yan, Yang Chang, Zhaosheng Chu, Yu Ling and Huan Wang

Int. J. Environ. Res. Public Health 2019, 16(18), 3244; https://doi.org/10.3390/ijerph16183244 - 4 Sep 2019

Cited by 24 | Viewed by 4292

Abstract

The filling ratio (FR) of a carrier has an influence on the pollutant removal of the aerobic moving bed biofilm reactor (MBBR). However, the effect of the polyethylene (PE) carrier FR on the performance and microbial characteristics of the denitrifying MBBR for the [...] Read more.

The filling ratio (FR) of a carrier has an influence on the pollutant removal of the aerobic moving bed biofilm reactor (MBBR). However, the effect of the polyethylene (PE) carrier FR on the performance and microbial characteristics of the denitrifying MBBR for the treatment of wastewater treatment plant (WWTP) effluent has not been extensively studied. A bench-scale denitrifying MBBR was set up and operated with PE carrier FRs of 20%, 30%, 40%, and 50% for the degradation of chemical oxygen demand (COD) and nitrogen from WWTP effluent at 12 h hydraulic retention time (HRT). The nitrate removal rates with FRs of 20%, 30%, 40%, and 50% were 94.3 ± 3.9%, 87.7 ± 7.3%, 89.7 ± 11.6%, and 94.6 ± 4.0%, and the corresponding denitrification rates (r_NO3--N) were 8.0 ± 5.6, 11.3 ± 4.6, 11.6 ± 4.6, and 10.0 ± 4.9 mg NO₃⁻-N/L/d, respectively. Nitrous oxide reductase (nosZ) gene-based terminal restriction fragment length polymorphism (T-RFLP) analysis illustrated that the highest functional diversity (Shannon’s diversity index, H′) of biofilm microbial community was obtained at 30% FR. The quantitative polymerase chain reaction (qPCR) results indicated that the abundance of nitrate reductase (narG) and nosZ genes at 30% FR was significantly higher than that at 20% FR, and no significant changes were observed at 40% and 50% FRs. Thus, 30% FR was recommended as the optimal carrier FR for the denitrifying MBBR. Full article

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15 pages, 2920 KiB

Open AccessArticle

Impact of an Extreme Winter Storm Event on the Coagulation/Flocculation Processes in a Prototype Surface Water Treatment Plant: Causes and Mitigating Measures

by Fuguo Qiu, Huadong Lv, Xiao Zhao and Dongye Zhao

Int. J. Environ. Res. Public Health 2019, 16(15), 2808; https://doi.org/10.3390/ijerph16152808 - 6 Aug 2019

Cited by 13 | Viewed by 4502

Abstract

Climate change has often caused failure in water treatment operations. In this study, we report a real case study at a major surface water treatment plant in Alabama, USA. Following a severe winter storm, the effluent water turbidity surged to >15.00 Nephelometric Turbidity [...] Read more.

Climate change has often caused failure in water treatment operations. In this study, we report a real case study at a major surface water treatment plant in Alabama, USA. Following a severe winter storm, the effluent water turbidity surged to >15.00 Nephelometric Turbidity Units (NTU), far exceeding the 0.30 NTU standard. As a result, the plant operation had to be shut down for three days, causing millions of dollars of losses and affecting tens of thousands of people. Systematic jar tests were carried out with sediment samples from 22 upstream locations. The coagulation and settleability of sediment particles were tested under simulated storm weather conditions, i.e., low temperature (7 °C) and in the presence of various types and concentrations of natural organic matter (NOM) that was extracted from the local sediments. Experimental results proved that elevated NOM (6.14 mg·L⁻¹ as Total Organic Carbon, TOC) in raw water was the root cause for the failure of the plant while the low temperature played a minor but significant role. Pre-oxidation with permanganate and/or elevated coagulant dosage were found effective to remove TOC in raw water and to prevent similar treatment failure. Moreover, we recommend that chemical dosages should be adjusted based on the TOC level in raw water, and a reference dosage of 0.29 kg-NaMnO₄/kg-TOC and 19 kg- polyaluminum chloride (PACl) /kg-TOC would be appropriate to cope with future storm water impacts. To facilitate timely adjustment of the chemical dosages, the real time key water quality parameters should be monitored, such as turbidity, TOC, Ultraviolet (UV) absorbance, pH, and color. The findings can guide other treatment operators to deal with shock changes in the raw water quality resulting from severe weather or other operating conditions. Full article

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11 pages, 1471 KiB

Open AccessArticle

Optimization of Polyaluminum Chloride-Chitosan Flocculant for Treating Pig Biogas Slurry Using the Box–Behnken Response Surface Method

by Yu Li, Leigang Li, Reham Yasser Farouk and Yuanyuan Wang

Int. J. Environ. Res. Public Health 2019, 16(6), 996; https://doi.org/10.3390/ijerph16060996 - 19 Mar 2019

Cited by 9 | Viewed by 3733

Abstract

Flocculation can remove large amounts of nitrogen and phosphorus from wastewater, and the resulting nitrogen- and phosphorus-rich floc can be used to produce organic fertilizer. For biogas slurries containing high levels of nitrogen and phosphorus, ordinary flocculants can no longer meet the flocculation [...] Read more.

Flocculation can remove large amounts of nitrogen and phosphorus from wastewater, and the resulting nitrogen- and phosphorus-rich floc can be used to produce organic fertilizer. For biogas slurries containing high levels of nitrogen and phosphorus, ordinary flocculants can no longer meet the flocculation requirements. In this study, to fully utilize the advantages of the two flocculants and achieve efficient removal rates of nitrogen and phosphorus from a biogas slurry, chitosan (CTS) and polyaluminum chloride (PAC) were used as a composite flocculation agent to flocculate pig biogas slurries. The response surface method was used to study the effect of PAC added (PAC_added) to the composite flocculant (CF), composite flocculant added (CF_added) to the biogas slurry and the pH on flocculation performance, and optimize these three parameters. In the tests, when the PAC_added was 6.79 g·100 mL⁻¹_CF, the CF_added was 20.05 mL·L⁻¹ biogas slurry and the pH was 7.50, the flocculation performance was the best, with an absorbance of 0.132 at a wavelength of 420 nm. The total phosphorus (TP) concentration was reduced from 214.10 mg·L⁻¹ to 1.38 mg·L⁻¹ for a removal rate of 99.4%. The total ammonia nitrogen (TAN) concentration was reduced from 1568.25 mg·L⁻¹ to 150.27 mg·L⁻¹ for a removal rate of 90.4%. The results showed that the CF could form larger flocs, and had greater adsorption capacity and more stable flocculation performance than ordinary flocculants. Furthermore, the CF could exhibit better chelation, electrical neutralization and bridge adsorption. Full article

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12 pages, 3453 KiB

Open AccessArticle

The Shock Effect of Inorganic Suspended Solids in Surface Runoff on Wastewater Treatment Plant Performance

by Li He, Tao Tan, Zhixi Gao and Leilei Fan

Int. J. Environ. Res. Public Health 2019, 16(3), 453; https://doi.org/10.3390/ijerph16030453 - 4 Feb 2019

Cited by 16 | Viewed by 4911

Abstract

Previous studies on the water quality of surface runoff often focused on the chemical oxygen demand (COD), nitrogen, phosphorus, and total suspended solid (TSS), but little is known in terms of the inorganic suspended solids (ISS). This research investigated the effects of ISS [...] Read more.

Previous studies on the water quality of surface runoff often focused on the chemical oxygen demand (COD), nitrogen, phosphorus, and total suspended solid (TSS), but little is known in terms of the inorganic suspended solids (ISS). This research investigated the effects of ISS carried by surface runoff on the treatment efficiency of the pretreatment facilities and the ratio of mixed liquor volatile suspended solid to mixed liquor suspended solid (MLVSS/MLSS) of the activated sludge in a wastewater treatment plant (WWTP) with the anaerobic-anoxic-oxic (AAO) process in Chongqing city, China. The results showed that the surface runoff had a long-lasting impact on the grit removal capacity of the grit chamber, affecting the normal operation after the rainfall. In contrast, the primary sedimentation tank showed strong impact resistance with higher removal rates of COD, TSS, and ISS. Nonetheless, the primary settling tank aggravates the removal of organic carbon in sewage during rainfall, having a negative impact on subsequent biological treatment. The ISS in the surface runoff could increase the sludge concentration and decrease the MLVSS/MLSS ratio. After repeated surface runoff impact, the MLVSS/MLSS ratio in the activated sludge would drop below even 0.3, interrupting the normal operation of WWTP. Full article

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13 pages, 1543 KiB

Open AccessArticle

Photocatalytic Mechanisms for Peroxymonosulfate Activation through the Removal of Methylene Blue: A Case Study

by Jorge Rodríguez-Chueca, Esther Alonso and Devendra Narain Singh

Int. J. Environ. Res. Public Health 2019, 16(2), 198; https://doi.org/10.3390/ijerph16020198 - 11 Jan 2019

Cited by 16 | Viewed by 5648

Abstract

Industrial activity is one of the most important sources of water pollution. Yearly, tons of non-biodegradable organic pollutants are discharged, at the least, to wastewater treatment plants. However, biological conventional treatments are unable to degrade them. This research assesses the efficiency of photocatalytic [...] Read more.

Industrial activity is one of the most important sources of water pollution. Yearly, tons of non-biodegradable organic pollutants are discharged, at the least, to wastewater treatment plants. However, biological conventional treatments are unable to degrade them. This research assesses the efficiency of photocatalytic activation of peroxymonosulfate (PMS) by two different iron species (FeSO₄ and Fe³⁺-citrate) and TiO₂. These substances accelerate methylene blue removal by the generation of hydroxyl and sulfate radicals. The required pH and molar ratios PMS:Fe are crucial variables in treatment optimization. The kinetic removal is reduced by the appearance of scavenger reactions in acidic and basic conditions, as well as by the excess of PMS or iron. The best performance is achieved using an Fe³⁺-citrate as an iron catalyst, reaching the total removal of methylene blue after 15 min of reaction, with a molar ratio of 3.25:1 (1.62 mM of PMS and 0.5 mM Fe³⁺-citrate). Fe³⁺-citrate reached higher methylene blue removal than Fe²⁺ as a consequence of the photolysis of Fe³⁺-citrate. This photolysis generates H₂O₂ and a superoxide radical, which together with hydroxyl and sulfate radicals from PMS activation attack methylene blue, degrading it twice as fast as Fe²⁺ (0.092 min⁻¹ with Fe²⁺ and 0.188 min⁻¹ with Fe³⁺-citrate). On the other hand, a synergistic effect between PMS and titanium dioxide (TiO₂) was observed (S_{PMS/TiO2/UV-A} = 1.79). This synergistic effect is a consequence of PMS activation by reaction with the free electron on the surface of TiO₂. No differences were observed by changing the molar ratio (1.04:1; 0.26:1 and 0.064:1 PMS:TiO₂), reaching total removal of methylene blue after 80 min of reaction. Full article

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15 pages, 2074 KiB

Open AccessArticle

Evaluation of Wastewater Treatment by Microcosms of Vertical Subsurface Wetlands in Partially Saturated Conditions Planted with Ornamental Plants and Filled with Mineral and Plastic Substrates

by Luis Sandoval, José Luis Marín-Muñiz, Sergio Aurelio Zamora-Castro, Fabiola Sandoval-Salas and Alejandro Alvarado-Lassman

Int. J. Environ. Res. Public Health 2019, 16(2), 167; https://doi.org/10.3390/ijerph16020167 - 9 Jan 2019

Cited by 18 | Viewed by 5582

Abstract

The current knowledge about the role terrestrial ornamental plants play in constructed wetlands (CWs) has scarcely been evaluated. Likewise, little attention has been given towards the use of new support or fill media for subsurface flow CWs, which may result in the reduction [...] Read more.

The current knowledge about the role terrestrial ornamental plants play in constructed wetlands (CWs) has scarcely been evaluated. Likewise, little attention has been given towards the use of new support or fill media for subsurface flow CWs, which may result in the reduction of costs when implemented on a large scale. This study evaluated, during nine months, the effect of three terrestrial ornamental plants and two substrates on the elimination of pollutants in wastewaters by using fill-and-drain vertical subsurface flow CWs (FD-CWs). Sixteen microcosms were used, nine filled with polyethylene terephthalate (PET) and nine with porous river stone (PRS). For each type of substrate, duplicates of microcosms were used, utilizing Anthurium sp., Zantedeschia aethiopica, and Spathiphyllum wallisii as vegetation and two other CWs without vegetation as controls. The environmental conditions, number of flowers, and height of the plants were registered. The results revealed that both substrates in the FD-CWs were efficient in removing pollutants. The average removal of pollutants in systems with vegetation revealed a positive effect on the reduction of the biochemical oxygen demand (55–70%), nitrates (28–44%), phosphates (25–45%), and fecal coliforms (52–65%). Meanwhile, in units without vegetation, the reduction of pollutants was nearly 40–50% less than in those with vegetation. The use of PET as a filling substrate in CWs did not affect the growth and/or the flowering of the species; therefore, its use combined with the species studied in CWs may be replicated in villages with similar wastewater problems. This may represent a reduction in implementation costs when utilizing PET recycled wastes and PRS as substrates in these systems in comparison with the typical substrates used in CWs. More studies are needed to better understand the interactions among these novel support media and the commercial terrestrial ornamental plants. Full article

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