| 1. |
- Anbalagan, Anbarasan, 1988-
(author)
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A passage to wastewater nutrient recovery units : Microalgal-Bacterial bioreactors
- 2018
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Artistic work (other academic/artistic)abstract
- In recent years, the microalgal–bacterial process has been considered to be a very attractive engineering solution for wastewater treatment. However, it has not been widely studied in the context of conventional wastewater treatment design under Swedish conditions. The technology holds several advantages: as a CO2 sink, ability to withstand cold conditions, ability to grow under low light, fast settling without chemical precipitation, and reducing the loss of valuable nutrients (CO2, N2, N2O, PO4). The process also provides the option to be operated either as mainstream (treatment of municipal wastewater) or side stream (treatment of centrate from anaerobic digesters) to reduce the nutrient load of the wastewater. Furthermore, the application is not only limited to wastewater treatment; the biomass can be used to synthesise platform chemicals or biofuels and can be followed by recovery of ammonium and phosphate for use in agriculture.In the present study, the feasibility of applying the process in Swedish temperature and light conditions was investigated by implementing microalgae within the activated sludge process. In this context, the supporting operational and performance indicators (hydraulic retention time (HRT), sludge retention time (SRT) and nutrients removal) were evaluated to support naturally occurring consortia in photo-sequencing and continuous bioreactor configuration. Furthermore, CO2 uptake and light spectrum-mediated nutrient removal were investigated to reduce the impact on climate and the technical challenges associated with this type of system.The results identified effective retention times of 6 and 4 days (HRT = SRT) under limited lighting to reduce the electrical consumption. From the perspective of nitrogen removal, the process demands effective CO2 input either in the mainstream or side stream treatment. The incorporation of a vertical absorption column demonstrated effective CO2 mass transfer to support efficient nitrogen and phosphorus removal as a side stream treatment. However, the investigation of a continuous single-stage process as the mainstream showed a requirement for a lower SRT in comparison to semi-continuous operation due to faster settlability, regardless of inorganic carbon. Furthermore, the process showed an effective reduction of influent phosphorus and organic compounds (i.e. COD/TOC) load in the wastewater as a result of photosynthetic aeration. Most importantly, the operation was stable at the temperature equivalent of wastewater (12 and 13 ˚C), under different lighting (white, and red-blue wavelengths) and retention times (6 and 1.5 d HRT) with complete nitrification. Additionally, the biomass production was stable with faster settling properties without any physiochemical separation.The outcomes of this thesis on microalgal–bacterial nutrient removal demonstrates that (1) photosynthesis-based aeration at existing wastewater conditions under photo-sequential and continuous photobioreactor setup, (2) flocs with rapid settling characteristics at all studied retention times, (3) the possibility of increasing carbon supplementation to achieve higher carbon to nitrogen balance in the photobioreactor, and (4) most importantly, nitrification-based microalgal biomass uptake occurred at all spectral distributions, lower photosynthetic active radiation and existing wastewater conditions.
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| 2. |
- Anbalagan, Anbarasan, et al.
(author)
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Continuous microalgae-activated sludge flocs for remediation of municipal wastewater under low temperature
- 2017
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Conference paper (peer-reviewed)abstract
- The operational performance of indigenous microalgae-activated sludge was evaluated regarding the nutrient removal efficiency using raw wastewater collected from Västerås wastewater treatment plant, Sweden at limited artificial surface lighting (290 μmol m-1 sec-1) and Nordic wastewater conditions (13°C). Additionally, the oxygen production and consumption, biomass concentration and its settling was evaluated during the symbiotic algal-bacterial interaction. The results confirmed oxygenic organic compound removal (COD removal of 65-94%) at higher (31-45 d) and lower (13-18 d) sludge retention time (SRT). Also, a complete removal of ammonium throughout the process and partial nitrite-nitrate removal at all SRTs (total nitrogen removal of 41- 62%) were observed. Likewise, a partial phosphorus (P)removal was observed in the effluent which provides an opportunity to capture free P fromthe effluent for recovery as fertiliser. Further, the microalgal growth was slower due to lightor inorganic carbon limitation or ammonium repression caused by higher internal recirculationas observed from ammonium and nitrite-nitrate levels in the PBR. Most importantly, effectivePBR biomass concentration based nutrient removal and relative sludge recirculation have tobe considered in the PBR design to avoid light limitation and activate symbiosis.
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| 3. |
- Anbalagan, Anbarasan, et al.
(author)
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Continuous photosynthetic abatement of CO2 and volatile organic compounds from exhaust gas coupled to wastewater treatment : Evaluation of tubular algal-bacterial photobioreactor
- 2017
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In: Journal of CO2 Utilization. - : Elsevier Ltd. - 2212-9820 .- 2212-9839. ; 21, s. 353-359
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Journal article (peer-reviewed)abstract
- The continuous abatement of CO2 and toluene from the exhaust gas by an indigenous microalgal-bacterial consortium was investigated in a pilot tubular photobioreactor interconnected to an absorption column using diluted centrate in seawater as a free nutrient source. The removal efficiency of CO2 and toluene was maximised in the vertical absorption column by identifying an optimum liquid to gas (L/G) ratio of 15. The photobioreactor supported steady-state nitrogen and phosphorus removals of 91 ± 2% and 95 ± 4% using 15% diluted centrate at 14 and 7 d of hydraulic retention time (HRT), respectively. A decrease in the removal efficiencies of nitrogen (36 ± 5%) and phosphorus (58 ± 10%) was recorded when using 30% diluted centrate at 7 d of HRT. The volumetric biomass productivities obtained at an HRT of 7 d accounted for 42 ± 11 and 80 ± 3 mg TSS L-1 d-1 using 15 and 30% centrate, respectively. Stable CO2 (76 ± 7%) and toluene removals (89 ± 5%) were achieved at an L/G ratio of 15 regardless of the HRT or centrate dilution. Hence, this study demonstrated the potential of algal-bacterial systems for the continuous removal of CO2 and volatile organic compounds from exhaust gas coupled with the simultaneous treatment of centrate.
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| 4. |
- Anbalagan, Anbarasan, 1988-
(author)
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Indigenous microalgae-activated sludge cultivation system for wastewater treatment
- 2016
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Licentiate thesis (other academic/artistic)abstract
- The municipal wastewater is mainly composed of water containing anthropogenic wastes that are rich in nutrients such as carbon, nitrogen and phosphorous. The cost for biological treatment of wastewater is increasing globally due to the population growth in urban cities. In general, the activated sludge (AS) process is a biological nutrient removal process used in wastewater treatment plants (WWTPs). The AS is composed of different microorganisms in which bacteria play a crucial role in wastewater treatment (WWT). During the process, air is bubbled to supply oxygen and methanol is added to improve nitrogen removal, which is released as a gas. Phosphorous is removed in the expense of precipitation chemicals. Altogether, the current process requires electrical energy, precipitation chemicals, handling of excess sludge and it emits carbon dioxide (CO2) as a by-product. This process is still in practise in the WWTPs since 1914 although numerous modifications are implemented to meet the stringent regulations in the European Union and globally.Microalgae are microorganisms that perform photosynthesis like plants. They are green and reproduce fast using available nutrients (nitrogen and phosphorous) and CO2 from their environment in the presence of light. As a result of photosynthesis, oxygen is released as waste gas. The synthesised oxygen during this process can be implemented to support the AS bacteria that leads to the microalgae activated sludge (MAAS) process. The main advantage is combined removal of nutrients.The vision of the research is to implement the indigenous microalgae cultivation in activated sludge process to consume CO2 and recover the nutrients from wastewater. This study is performed to improve the understanding of the process such as: light utilisation, nutrient removal and recovery of the biomass from wastewater in closed photo-bioreactors. Photo-bioreactors are vessels where the cultivation is carried out in the presence of light. At first, the influence of the light spectrum on micro-algal cultivation is investigated for photosynthetic growth. This is followed by operational challenges of the microalgae cultivation during the AS process. The process is experimentally performed in the photo-bioreactors with different treatment time of the raw wastewater. The results showed that 2 - 6 days of treatment time can be used for reducing nutrients in wastewater if the process is optimised further. Also, nutrient ratio is analysed for the availability of the micro-algal growth. Furthermore, the biogas potential of MAAS showed a biogas yield of about 60-80% within 5 to 9 days.At last, the experimental verification of chemically precipitated wastewater showed limitation of phosphorous for micro-algal growth. Additionally, the optimal oxygen supply through light response is verified for photo-bioreactors. The outcome of this study shows that knowing the right conditions can lower the treatment time. By doing so, a stable nutrient removal and reduction of precipitation chemicals can be established as well as a better recovery of valuable nutrients as phosphorous and nitrogen.
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| 5. |
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| 6. |
- Anbalagan, Anbarasan, et al.
(author)
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Influence of hydraulic retention time on indigenous microalgae and activated sludge process
- 2016
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In: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 91, s. 277-284
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Journal article (peer-reviewed)abstract
- Integration of the microalgae and activated sludge (MAAS) process in municipal wastewater treatment and biogas production from recovered MAAS was investigated by studying the hydraulic retention time (HRT) of semi-continuous photo-bioreactors. An average total nitrogen (TN) removal efficiency (RE) of maximum 81.5 ± 5.1 and 64.6 ± 16.2% was achieved at 6 and 4 days HRT. RE of total phosphorous (TP) increased slightly at 6 days (80 ± 12%) HRT and stabilized at 4 days (56 ± 5%) and 2 days (55.5 ± 5.5%) HRT due to the fluctuations in COD and N/P mass ratio of the periodic wastewater. COD and organic carbon were removed efficiently and a rapidly settleable MAAS with a sludge volume index (SVI_10) of less than 117 mL g-1 was observed at all HRTs. The anaerobic digestion of the untreated MAAS showed a higher biogas yield of 349 ± 10 mL g VS-1 with 2 days HRT due to a low solids retention time (SRT). Thermal pretreatment of the MAAS (120 °C, 120 min) did not show any improvement with biogas production at 6 days (269 ± 3 (untreated) and 266 ± 16 (treated) mL gVS-1), 4 days (258 ± 11(untreated) and 263 ± 10 (treated) mL gVS-1) and 2 days (308 ± 19 mL (treated) gVS-1) HRT. Hence, the biogas potential tests showed that the untreated MAAS was a feasible substrate for biogas production. Results from this proof of concept support the application of MAAS in wastewater treatment for Swedish conditions to reduce aeration, precipitation chemicals and CO2 emissions.
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| 7. |
- Anbalagan, Anbarasan, et al.
(author)
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Influence of iron precipitated condition and light intensity on microalgae activated sludge based wastewater remediation
- 2017
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In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; , s. 1523-1530
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Journal article (peer-reviewed)abstract
- The indigenous microalgae-activated sludge (MAAS) process during remediation of municipal wastewater was investigated by studying the influence of iron flocculation step and light intensity. In addition, availability of total phosphorous (P) and photosynthetic activity was examined in fed-batch and batch mode under northern climatic conditions and limited lighting. This was followed by a semi-continuous operation with 4 d of hydraulic retention time and mean cell residence time of 6.75 d in a photo-bioreactor (PBR) with varying P availability. The fed-batch condition showed that P concentrations of 3–4 mg L−1 were effective for photosynthetic chl. a development in iron flocculated conditions. In the PBR, the oxygen evolution rate increased with increase in the concentration of MAAS (from 258 to 573 mg TSS L−1) at higher surface photosynthetic active radiation (250 and 500 μmol m−2 s−1). Additionally, the rate approached a saturation phase at low MAAS (110 mg L−1) with higher light intensities. Semi-continuous operation with luxury P uptake and effective P condition showed stable average total nitrogen removal of 88 and 92% respectively, with residual concentrations of 3.77 and 2.21 mg L−1. The corresponding average P removal was 68 and 59% with residual concentrations of 2.32 and 1.75 mg L−1. The semi-continuous operation produced a rapidly settleable MAAS under iron flocculated condition with a settling velocity of 92–106 m h−1 and sludge volume index of 31–43 ml g−1 in the studied cases.
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| 8. |
- Anbalagan, Anbarasan, et al.
(author)
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Influence of light emitting diodes on indigenous microalgae cultivation in municipal wastewater
- 2015
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In: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 75, s. 786-792
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Journal article (peer-reviewed)abstract
- In this study, the effect of light emitting diodes (LEDs) on microalgae cultivation in municipal wastewater was examined in comparison to the fluorescent light. Two kinds of wastewater were evaluated: first one with low concentration of total phosphorous (TP) and second one with high TP concentration. The nutrient removal and biomass production using LEDs is efficient at photo-synthetically active radiation (PAR) intensity of 107-112 mu mol m(-2) s(-1) which is slightly higher than fluorescent light. Furthermore, this study demonstrates the applicability and distribution of light in wastewater where the environment is not defined. More importantly, winter and rainy periods contribute to dark condition and dilution of wastewater, intense LED light offers a feasible option for the functioning of closed micro algae based activated sludge (MAAS) process for recovery and reuse of nutrients.
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| 9. |
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| 10. |
- Punzi, Marisa, et al.
(author)
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Combined anaerobic-ozonation process for treatment of textile wastewater : Removal of acute toxicity and mutagenicity
- 2015
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In: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 292, s. 52-60
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Journal article (peer-reviewed)abstract
- A novel set up composed of an anaerobic biofilm reactor followed by ozonation was used for treatment of artificial and real textile effluents containing azo dyes. The biological treatment efficiently removed chemical oxygen demand and color. Ozonation further reduced the organic content of the effluents and was very important for the degradation of aromatic compounds, as shown by the reduction of UV absorbance. The acute toxicity toward Vibrio fischeri and the shrimp Artemia salina increased after the biological treatment. No toxicity was detected after ozonation with the exception of the synthetic effluent containing the highest concentration, 1. g/l, of the azo dye Remazol Red. Both untreated and biologically treated textile effluents were found to have mutagenic effects. The mutagenicity increased even further after 1. min of ozonation. No mutagenicity was however detected in the effluents subjected to longer exposure to ozone. The results of this study suggest that the use of ozonation as short post-treatment after a biological process can be beneficial for the degradation of recalcitrant compounds and the removal of toxicity of textile wastewater. However, monitoring of toxicity and especially mutagenicity is crucial and should always be used to assess the success of a treatment strategy. © 2015 Elsevier B.V.
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