Research

11 pages, 3283 KiB

Open AccessArticle

Using Natural and Artificial Microalgal-Bacterial Granular Sludge for Wastewater Effluent Polishing

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Water 2023, 15(14), 2605; https://doi.org/10.3390/w15142605 - 18 Jul 2023

Viewed by 757

Abstract

Marimo is a type of microalgal-bacterial granular sludge (MBGS) that exists in natural water bodies. For the first time, this paper explored the feasibility of marimo in real wastewater effluent polishing, focusing on nutrient removal as compared with MBGS. The results showed that [...] Read more.

Marimo is a type of microalgal-bacterial granular sludge (MBGS) that exists in natural water bodies. For the first time, this paper explored the feasibility of marimo in real wastewater effluent polishing, focusing on nutrient removal as compared with MBGS. The results showed that the color of marimo gradually darkened during a 21-day experiment, and the chlorophyll content increased significantly. Although marimo and MBGS showed fairly similar removal performance in terms of NO₃⁻-N and TN, marimo exhibited better phosphate removal as compared to MBGS. Marimo and MBGS contained different algae but the same bacterial phylum of Proteobacteria, including denitrifiers. In addition, marimo had a higher relative abundance of nitrite reductase than MBGS, suggesting that the denitrification process might also happen in addition to assimilation. This study is expected to initiate the application of marimo for wastewater effluent polishing and reclamation, shedding light on nature-based wastewater self-purification technology in the era of carbon neutrality. Full article

(This article belongs to the Special Issue Nitrification-Denitrification Processes in Bioreactors for Wastewater and Sludge Treatment)

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15 pages, 3983 KiB

Open AccessArticle

Roles of Granular Sludge Size Restricting and Organic Degradation in an Extended Filamentous AGS System Using Agnail Aeration Device

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Water 2023, 15(11), 2009; https://doi.org/10.3390/w15112009 - 25 May 2023

Viewed by 790

Abstract

This work investigated the role of an agnail device (manually made from a comb) on sludge size restriction and organic degradation in extended filamentous aerobic granular sludge-sequencing batch reactors (AGS-SBRs) with artificial wastewater. Two identical SBRs (R1 and R2) were employed in this [...] Read more.

This work investigated the role of an agnail device (manually made from a comb) on sludge size restriction and organic degradation in extended filamentous aerobic granular sludge-sequencing batch reactors (AGS-SBRs) with artificial wastewater. Two identical SBRs (R1 and R2) were employed in this experiment. Extended filamentous AGS with a large size was achieved in both SBRs by seeding the dewatering the sludge on day 40. R1 (the control) did not use the agnail aeration device, and the extended filamentous AGS system was finally disintegrated. However, R2 promptly employed the agnail device on days 56–59, the extended filamentous AGS size obviously decreased from 4.8 mm to 2.5 mm, and the dominant filamentous species, including Proteobacteria, Acidobacteria, and Choroflexi, gradually shrank at a low level, acting as a framework for AGS recovery. This was because enough nutrients diffused into the inside of small sludge for the filamentous living. Simultaneously, the sludge volume indexes (SVI₅ and SVI₃₀) sharply decreased from 155.8–103.9 to 51.7–46.6 mL/g, and the mixed liquid suspended solids (MLSSs) and extracellular polymeric substances (EPSs) in R2 both increased and were kept at 5816 mg/L and 69.1 mg/g·MLVSS, respectively. These contributed to enhancing the sludge’s structural stability to avoid AGS failure. COD and NH₄⁺-N in R2 were both degraded by simultaneous nitrification and denitrification (SND) processes throughout the experiment, which was not significantly influenced before or after the agnail aeration device was employed. These results indicate that the agnail device can effectively restrict AGS size and limit the extended filamentous overgrowth with nutrient diffusion into the sludge’s interior, which can prevent AGS disintegration. In addition, this device had no significant influence on organic degradation. Full article

(This article belongs to the Special Issue Nitrification-Denitrification Processes in Bioreactors for Wastewater and Sludge Treatment)

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15 pages, 1837 KiB

Open AccessArticle

Controlling Nitrogen Removal Processes in Improved Vertical Flow Constructed Wetland with Hydroponic Materials: Effect of Influent COD/N Ratios

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Elackiya Sithamparanathan

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Nora B. Sutton

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Huub H. M. Rijnaarts

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Katarzyna Kujawa-Roeleveld

Water 2023, 15(6), 1074; https://doi.org/10.3390/w15061074 - 10 Mar 2023

Cited by 1 | Viewed by 1282

Abstract

Discharge of nitrogen (N) with wastewater causes eutrophication in surface water. On the other hand, nutrient-rich wastewater can be valuable for agriculture. Tailoring N removal or conservation is important to meet the requirements of different water end uses. Improved vertical flow constructed wetlands [...] Read more.

Discharge of nitrogen (N) with wastewater causes eutrophication in surface water. On the other hand, nutrient-rich wastewater can be valuable for agriculture. Tailoring N removal or conservation is important to meet the requirements of different water end uses. Improved vertical flow constructed wetlands with hydroponic materials (CWH) as substrata were developed at lab scale in a greenhouse and studied to optimize N removal in CWH. This study investigated the effect of influent COD/N ratios of 5/1 and 15/1 on the removal or conservation of N in CWHs with Syngonium as vegetation and three substrata, pumice, cocopeat, and mineral wool. CWH with pumice showed the highest TN removal at both COD/N ratios. The Syngonium plant significantly contributed to the additional 50% TN removal in CWH. Nitrification of above 90% was observed at both studied COD/N ratios, indicating sufficient oxygenation due to the vertical pulse flow operated CWH. The denitrification process was enhanced at a higher COD/N ratio of 15/1 compared to 5/1 by around 10–40%. The occurring nitrification and denitrification indicate the coexistence of aerobic and anaerobic conditions in CWH, and balancing these conditions is necessary for future applications to remove N for its specific end use, i.e., irrigation water (high standards) or discharge to surface water (low standards). Full article

(This article belongs to the Special Issue Nitrification-Denitrification Processes in Bioreactors for Wastewater and Sludge Treatment)

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13 pages, 2946 KiB

Open AccessArticle

The Pretreatment of Micro-Polluted Source Water through Phototrophic Biofilms under Variant Light Conditions

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Water 2023, 15(4), 621; https://doi.org/10.3390/w15040621 - 05 Feb 2023

Viewed by 1163

Abstract

The imbalance of inorganic nutrients in micro-polluted source water poses a huge threat to aquatic environments and human health. To pretreat micro-polluted source water, some biological reactors have been conducted at lab-scale. However, using phototrophic biofilms to pretreat micro-polluted source water at pilot-scale [...] Read more.

The imbalance of inorganic nutrients in micro-polluted source water poses a huge threat to aquatic environments and human health. To pretreat micro-polluted source water, some biological reactors have been conducted at lab-scale. However, using phototrophic biofilms to pretreat micro-polluted source water at pilot-scale has yet to be explored, and the effects of light on the practical operation of phototrophic biofilms are poorly understood. In this study, the potential of pretreating micro-polluted source water by phototrophic biofilms was explored. The high light intensity (4500 lx, 60.75 μmol/m²/s) promoted the growth of phototrophic biofilms and the secretion of extracellular polymeric substance. The removal efficiency of inorganic nitrogen and total phosphorus in synthetic micro-polluted water was 56.82% and 40.90%, respectively. When interacting with actual micro-polluted source water, the nutrients in the actual micro-polluted source water were reduced by the stable pilot-scale phototrophic biofilms. The final concentration of effluent nutrients was lower than the Grade II surface water quality standard in China. Therefore, using phototrophic biofilms as a pretreatment facility in water treatment plants is a promising solution to this issue. Full article

(This article belongs to the Special Issue Nitrification-Denitrification Processes in Bioreactors for Wastewater and Sludge Treatment)

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13 pages, 2805 KiB

Open AccessArticle

Results of Adding Sludge Micropowder for Microbial Structure and Partial Nitrification and Denitrification in a Filamentous AGS-SBR Using High-Ammonia Wastewater

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Water 2023, 15(3), 508; https://doi.org/10.3390/w15030508 - 27 Jan 2023

Cited by 2 | Viewed by 1274

Abstract

This work investigated the roles of sludge micropowder addition in microbial structure and partial nitrification and denitrification (PND) in an extended filamentous aerobic granular sludge-sequencing batch reactor (AGS-SBR) using high-ammonia wastewater. Type 1683 Acinetobacter with a high percentage became the dominant extended filaments, [...] Read more.

This work investigated the roles of sludge micropowder addition in microbial structure and partial nitrification and denitrification (PND) in an extended filamentous aerobic granular sludge-sequencing batch reactor (AGS-SBR) using high-ammonia wastewater. Type 1683 Acinetobacter with a high percentage became the dominant extended filaments, remarkably shifted and remained at a low level, acting as a framework for AGS recovery after micropowder addition. The sludge volume index (SVI₅) decreased from 114 to 41.7 mL/g, mixed liquid suspended solids (MLSS) and extracellular polymers (EPS) both increased and balanced at 6836 mg/L and 113.4 mg/g•MLVSS, respectively. COD and NH₄⁺-N were degraded to certain degrees in the end. However, the effluent NO₂⁻-N accumulated to the peak value of 97.6 mg/L on day 100 (aeration stage), then decreased and remained at 45.3 mg/L with development of the stirring and micropowder supplemented in the SBR on day 160 (anoxic stage), while the influent NO₂⁻-N always remained at zero. Interestingly, the influent/effluent NO₃⁻-N both remained at zero throughout the whole experiment. These results demonstrated that PND was successfully obtained in this work. Sludge micropowder addition not only restrained the extended filaments’ overgrowth, but also contributed to PND realization with carbon released. Citrobacter and Thauera played an essential role in the PND process for high-ammonia wastewater treatment. Running condition, wastewater characteristic, and sludge structure played an important role in microbial composition. Full article

(This article belongs to the Special Issue Nitrification-Denitrification Processes in Bioreactors for Wastewater and Sludge Treatment)

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10 pages, 2249 KiB

Open AccessArticle

Nutrients’ Removal from Mariculture Wastewater by Algal–Bacterial Aggregates Developed from Spirulina platensis

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Water 2023, 15(3), 396; https://doi.org/10.3390/w15030396 - 18 Jan 2023

Cited by 1 | Viewed by 1690

Abstract

As an important alternative to alleviate the shortage of wild fishery resources, mariculture is facing increasing challenges on the wastewater treatment, mainly due to the salinity brought from seawater and low nutrient concentration. In this study, Spirulina platensis (S. platensis) was [...] Read more.

As an important alternative to alleviate the shortage of wild fishery resources, mariculture is facing increasing challenges on the wastewater treatment, mainly due to the salinity brought from seawater and low nutrient concentration. In this study, Spirulina platensis (S. platensis) was adopted as the target algae stain for synthetic mariculture wastewater treatment, which exhibited excellent adaptability to high-saline wastewater during a 40 days’ adaptive culture. Then, the microalgae stain was inoculated into photo-bioreactors with different uplift airflow velocity (UAV) to achieve microalgal aggregation. After 10 days of pre-cultivation and a 30-day granulation process, the maximum nutrient removal rates by S. platensis were 86.5% of TN (to 3.4 mg/L), 98.1% of TP (to 0.1 mg/L) and 95.8% of DOC (to 5.5 mg/L), with 3.5 g/L of biomass content in synthetic wastewater. Analysis of phosphorus and EPS content showed that higher protein content in tightly bound EPS and enhanced P accumulation was accompanied with the microalgal aggregation processes, and P was mainly distributed in the residual rather than the EPS part of microalgal aggregates, indicating that the development of aggregates from suspension S. platensis would benefit not only biomass separation, but also phosphorus recovery, being a potential treatment for simultaneously removing nutrients and recovering mariculture wastewater. Full article

(This article belongs to the Special Issue Nitrification-Denitrification Processes in Bioreactors for Wastewater and Sludge Treatment)

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15 pages, 2958 KiB

Open AccessArticle

Sequential Nitrification—Autotrophic Denitrification Using Sulfur as an Electron Donor and Chilean Zeolite as Microbial Support

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Water 2023, 15(1), 95; https://doi.org/10.3390/w15010095 - 28 Dec 2022

Viewed by 1485

Abstract

Sequential nitrification–autotrophic denitrification (SNaD) was carried out for ammonium removal in synthetic wastewater (SWW) using sulfur as an electron donor in denitrification. Four reactors were operated in batch mode, two with zeolite (1 mm size) used as microbial support and two without support, [...] Read more.

Sequential nitrification–autotrophic denitrification (SNaD) was carried out for ammonium removal in synthetic wastewater (SWW) using sulfur as an electron donor in denitrification. Four reactors were operated in batch mode, two with zeolite (1 mm size) used as microbial support and two without support, to assess the effect of the zeolite addition in the SNaD. Aeration, anoxic, and anaerobic cycles were established, where 96% removal of NH₄⁺-N (oxidized to nitrite or nitrate) was achieved in nitrification, along with 93% removal of NO₃⁻-N in denitrification for the SNaD with zeolite. It was observed that the use of zeolite assists in buffering reactor load changes. Inhibition caused by nitrite accumulation in the denitrification stage was minimized by increasing the nitrogen concentration in the SWW. The results obtained in this study are the basis for the development of ammonium removal by simultaneous nitrification–autotrophic denitrification using a single reactor. Full article

(This article belongs to the Special Issue Nitrification-Denitrification Processes in Bioreactors for Wastewater and Sludge Treatment)

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13 pages, 2093 KiB

Open AccessArticle

Removal of N and P in a Rotating Biological Contactor Plant: Case Study Agnita, Romania

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Eniko Gaspar

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Ioan Munteanu

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Silviu Sintea

Water 2022, 14(22), 3670; https://doi.org/10.3390/w14223670 - 14 Nov 2022

Viewed by 1402

Abstract

The wastewater treatment plant of Agnita, Romania was designed with a rotational biological contactor system for a population of approximately 9500, but for environmental protection reasons it must comply with regulations concerning nitrogen and phosphorus designed for larger communities. In order to achieve [...] Read more.

The wastewater treatment plant of Agnita, Romania was designed with a rotational biological contactor system for a population of approximately 9500, but for environmental protection reasons it must comply with regulations concerning nitrogen and phosphorus designed for larger communities. In order to achieve the prescribed limits for these pollutants, we have used a 40% FeCl₃ solution, continuously added to the distributor, without changes in flow or equipment. Its use boosts the removal of ammonia nitrogen, and phosphorus, bringing them within the limits and with reasonable cost. To determine the ferric chloride to be used we considered, aside from the pollutant load, the water temperature, and introduced a new parameter: specific removal power that enabled us to optimize the volume of FeCl₃. A major contribution to nitrogen removal was achieved by the denitrification bacteria favored by the presence of ferric ions, which also precipitate phosphorus. The results of this study, performed since September 2021, enable us to continue to use this method and enlarge its application to other plants owned by the local operator. Full article

(This article belongs to the Special Issue Nitrification-Denitrification Processes in Bioreactors for Wastewater and Sludge Treatment)

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