Comparative Study on Treatment of Municipal Wastewater with Carbondioxide Sequestration by Microalgae

Transcription

1 International Journal of ChemTech Research CODEN( USA): IJCRGG ISSN : Vol.6, No.1, pp , Jan-March 2014 Comparative Study on Treatment of Municipal Wastewater with Carbondioxide Sequestration by Microalgae Gokulan Ravindiran 1 *, Ragunath.S 2 1 Assistant professor, Department of Civil Engineering, KPR Institute of Engineering and Technology, Coimbatore,India. 2 Assistant professor (SL.G), Department of Civil Engineering, KPR Institute of Engineering and Technology, Coimbatore,India. *Corres.author: gokulravi4455@gmail.com Phone: Abstract: The world is faced with an intrinsic environmental responsibility, i.e. Minimization of greenhouse gas emission to an acceptable level. This study seeks to explain one of the methods for carbon dioxide capture and sequestration, to reduce the greenhouse effect in sustainable manner. Though power generation is one of the major contributors for co 2 emission, utilizing coal/lignite for power generation has become a compulsive need for fast growing economies like India and china to meet the demand/ supply gap in power availability. Out of several co 2 sequestration methods, biological method of co 2 sequestration is better because the process is less energy intensive. Algae are autotrophic microorganisms capable of converting co 2 into carbohydrates and lipids in the presence of light by photosynthesis. Algae are the fastest growing photosynthetic organism having a carbon fixation rate more than any other organisms. In these study microalgae is cultivated for the treatment of municipal wastewater and carbondioxide sequestration. The work is carried out at two different stages i.e., wastewater treatment without carbondioxide sequestration and wastewater treatment with carbondioxide sequestration from coal. From the results we concluded that the microalgae can be effectively used for the treatment of wastewater and carbondioxide sequestration. So, Algal photosynthetic reaction may hold the key to reducing emission in both economically and environmentally sustainable manner. Renewable form of energy can be produced from this algal biomass & many other useful products can also be produced. Key words: Carbon dioxide, microalgae, renewable energy, municipal wastewater.

2 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Introduction: Wastewater derived from municipal, agricultural & industrial activities is a source of nutrients for microalgae cultivation [6]. In addition, microalgae-based systems can significantly reduce both organic matter and nutrients in municipal and piggery wastewater at minimal energy cost [3], [7], [9]. The use of wastewater could reduce the need for additional Nitrogen & phosphorus sources by approximately 55% [8]. Microalgae cultures offer an effective solution to tertiary & quaternary wastewater treatment due to the ability of microalgae to use inorganic nitrogen &phosphorus for their growth[5]. One promising way to make algal biofuel production more cost effective is to integrate wastewater treatment with algal biomass production [2]. The most suitable concentration for the growth microalge in airlift reactor with cyclic axial mixing of media is 5% CO 2 (v/v) [5]. The bioreactor was capable of utilizing CO 2 in the flue gas of a power plant as the carbon source[1]. This study focuses on the potential for using microalgae isolated from waste stabilization ponds in order to reduce the organic& inorganic pollutants from municipal wastewater with carbon dioxide sequestration. Methods and Materials: Selection Of Municipal Wastewater: The municipal waste water used in this process is collected from Karuvadikuppam Sewage Treatment Plant, Lawspet, Puducherry. The sample is collected at the inlet of the sewage treatment plant. Selection Of Algal Inoculum: The algal inoculum used in this process is collected from karuvadikuppam sewage Treatment Plant, Laws pet, Pondicherry. The sample is collected from waste stabilization pond. Microalgae Identification: The sample is examined for microalgae identification. Experimental Scheme: The nutrient uptake and biomass growth of algae were studied under two stages. The stage I was concentrated on the removal of nutrient and biomass production without carbon dioxide sequestration under batch systems at different dilution ratios and the stage II was concentrated on the removal of nutrient and biomass production with carbon dioxide sequestration from coal under batch systems at different dilution ratios. Stage I: Biomass Activity without Carbon dioxide Sequestration: The tests were carried out in a 10 liters plastic can s with a working volume of 7 liters for various proportion of municipal sewage and algal inoculum as shown in table 2. the canes were kept at average ambient temperature varying from o C and the canes are opened at the top completely, so that it is exposed to open environment. The analytical procedures were carried out for the above mentioned dilution ratios daily for a period of 10 days. Daily 100 ml of the sample is taken from the batch reactor for testing and it is replaced by the same dilution ratio. The wastewater and algal inoculums are collected from the same place with a interval of 2 days.

3 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Table 1: Average Physicochemical characteristics of Raw Municipal Wastewater and Algae inoculums: SI.NO PARAMETERS UNITS 01 Color MUNICIPAL WASTEWATER ALGAE INOCULUM 2 ND DAY 5 TH DAY 7 TH DAY 10 TH DAY 2 ND DAY 5 TH DAY 7 TH DAY 10 TH DAY Greyish Black Greyish Black Greyish Black Greyish Black Light Green Light Green Light Green Light Green 02 ph E.C ms Temperature C Dissolved Oxygen mg/l BOD mg/l COD mg/l Hardness mg/l Alkalinity mg/l Chloride mg/l Sulphate mg/l Manganese mg/l Phosphorus mg/l TKN mg/l TS mg/l TDS mg/l TSS mg/l TVS mg/l TVDS mg/l TVSS mg/l

4 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Table 2: Dilution ratios for biomass activity without carbon dioxide sequestration Batch Reactor Raw Sewage (%) Algal Inoculum (%) Raw Sewage In (Litres) Algal Inoculum In (Litres) CONTROL Stage II: Biomass activity with carbon dioxide sequestration (COAL): The tests were carried out in 10 liters plastic can s with a working volume of 7 liters for various proportion of municipal sewage and algal inoculum as shown in table 3. The canes were kept at average ambient temperature varying from O C and the canes are provided inside with a setup, such that coal can be burned inside the batch reactors there by providing carbon dioxide for sequestration 5 grams of coal is burned daily at morning 9.00 am and evening 4.00 pm respectively. The analytical procedures were carried out for the above mentioned dilution ratios daily for a period of 10 days. Daily 100 ml of the sample is taken from the batch reactor for testing and it is replaced by the same dilution ratio. The wastewater and algal inoculums are collected from the same place with a interval of 2 days. Table 3: Dilution ratios for biomass activity with carbon dioxide sequestration Batch Reactor Raw Sewage (%) Algal Inoculum Raw Sewage Algal Inoculum (%) (Liters) (Liters) Results and Discussion: Stage I: Biomass Activity without Carbon dioxide Sequestration: Microalgae identification: The prominent genera s identified are Anabaena, Diatoms, Hyalophacus, Monoraphidium, Navicula, Oscillatoria and Spirogyra. Phosphorus: The phosphorus content is also considered as monitoring parameter. The 0 th day Phosphorus concentration were varied between 63 mg/l to 44 mg/l. After 10 days of algal cultivation, the total phosphorus content were reduced from 55 mg/l to 12 mg/l, 63 mg/l to 10 mg/l, 60 mg/l to 10 mg/l, 61 mg/l to 11 mg/l, 46 mg/l to 11 mg/l, 44 mg/l to 10 mg/l and their removal efficiency were around 78%, 84%, 83%, 72%, 76%, 73%, for the respective batch ractors ( 01,02,03,04,05, CONTROL).The variation of the phosphorus in the batch reactors is shown in figure 1.

5 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Figure 1: Variation of Phosphorus with respect to different dilution ratios (Without carbon dioxide sequestration): Total Kjeldahl Nitrogen: The Total Kjeldahl Nitrogen content is also considered as monitoring parameter. The 0 th day Total kjeldhal Nitrogen concentration were varied between 68 mg/l to 36 mg/l. After 10 days of algal cultivation, the Total kjeldhal Nitrogen content were reduced from 68 mg/l to 6 mg/l, 62 mg/l to 9 mg/l, 65 mg/l to 13 mg/l, 60 mg/l to 20mg/L, 64 mg/l to 29 mg/l, 36 mg/l to 5 mg/l and their removal efficiency were around 91%, 85%, 80%, 66%, 55%, 86%, for the respective batch reactors ( 01,02,03,04,05, CONTROL). There is a decrease in the Total kjeldhal nitrogen content during algae cultivation. The variation of the Total Kjeldahl Nitrogen in the batch reactors is shown figure 2. Figure 2: Variation of Total kjeldhal Nitrogen with respect to different dilution ratios (without carbon dioxide sequestration):

6 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Chemical Oxygen Demand: The Chemical Oxygen Demand is also considered as monitoring parameter. The 0 th day Chemical oxygen Demand concentration were varied between 430 mg/l to 240 mg/l. After 10 days of algal cultivation, the Chemical oxygen Demand content were reduced from 410 mg/l to 250 mg/l, 240 mg/l to 220 mg/l, 280 mg/l to 230 mg/l, 430 mg/l to 210mg/L, 330 mg/l to 260 mg/l, 300 mg/l to 240 mg/l and their removal efficiency were around 40%, 10%, 08%, 52%, 22%, 20%, for the respective Batch Cultures ( 01,02,03,04,05, CONTROL). There is a decrease in the Chemical Oxygen Demand during algae cultivation. The variation of the Chemical Oxygen Demand in the batch reactors is shown in figure 3. Figure 3: Variation of Chemical Oxygen Demand with respect to different dilution ratios (without carbon dioxide sequestration): Total Dissolved Solids: The Total Dissolved Solids is also considered as monitoring parameter. The 0 th day Total Dissolved Solids concentration were varied between 1470 mg/l to 1080 mg/l. After 10 days of algal cultivation, the Total Dissolved Solids content were increased from 1410 mg/l to 1420 mg/l, 1430 mg/l to 1500 mg/l, 1460 mg/l to 1520 mg/l, 1470 mg/l to 1540 mg/l, 1470 mg/l to 1550 mg/l, 1080 mg/l to 1260 mg/l and their growth efficiency were around 0.04%, 0.05%, 0.04%, 0.04%, 0.05%, 0.16%, for the respective Batch Cultures (01,02,03,04,05, CONTROL). Of all the batch cultures CONTROL showed the greater increased efficiency. There is an increase in the total dissolved solids during algae cultivation. The variation of the TDS in the batch reactors is shown in figure 4.

7 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Figure 4: Variation of Total Dissolved Solids with respect to different dilution ratios (without carbon dioxide sequestration). Stage II: Biomass activity with carbon dioxide sequestration (COAL): Microalgae identification: Phosphorus: The prominent genera s identified are Arthrospira, Scenedesmus. The phosphorus content is also considered as monitoring parameter. Phosphorus concentration were varied between 30 mg/l to 05 mg/l. After 10 days of algal cultivation, the total phosphorus content were reduced from 26 mg/l to 10 mg/l, 27 mg/l to 08 mg/l, 30 mg/l to 08 mg/l, and their removal efficiency were around 61%, 70%, 73% for the respective Batch Cultures (01,02,03). Of all the batch reactors 03 showed the greater removal efficiency. The variation of the phosphorus in the batch reactors is shown in figure 5. Figure 5: Variation of Phosphorus with respect to carbon dioxide sequestration from coal.

8 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Total Kjeldhal Nitrogen: The Total Kjeldahl Nitrogen content is also considered as monitoring parameter. Total kjeldhal Nitrogen values were varied between 48 mg/l to 18 mg/l. After 10 days of algal cultivation, the Total kjeldhal Nitrogen content were reduced from 46 mg/l to 18 mg/l, 42 mg/l to 18 mg/l, 48 mg/l to 20 mg/l, and their removal efficiency were around 60%, 57%, 58%, for the respective batch cultures (01,02,03). There is a decrease in the Total kjeldhal nitrogen content during algae cultivation. Of all the batch reactors 01 showed the greater removal efficiency. The variation of the Total Kjeldahl Nitrogen in the batch reactors is shown in figure 6. Figure 6: Variation of Total kjeldhal Nitrogen with respect to carbon dioxide sequestration from coal. Chemical Oxygen Demand: The Chemical Oxygen Demand is also considered as monitoring parameter. Chemical oxygen Demand values were varied between 360 mg/l to 70 mg/l. After 10 days of algal cultivation, the Chemical oxygen Demand content were reduced from 230 mg/l to 70 mg/l, 340 mg/l to 80 mg/l, 360 mg/l to 90 mg/l, and their removal efficiency were around 55%, 62%, 61%, for the respective Batch Cultures ( 01,02,03). There is a decrease in the Chemical Oxygen Demand during algae cultivation. Of all the batch reactors 02 showed the greater removal efficiency.the variation of the Chemical Oxygen Demand in the batch reactors is shown in figure 7. Figure 7: Variation of Chemical Oxygen Demand with respect to carbon dioxide sequestration from coal.

9 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Total Dissolved Solids: The Total Dissolved Solids is also considered as monitoring parameter. Total Dissolved Solids values were varied between 1390 mg/l to 1700 mg/l. After 10 days of algal cultivation, the Total Dissolved Solids content were increased from 1460 mg/l to 1700 mg/l, 1420 mg/l to 1680 mg/l, 1420 mg/l to 1670 mg/l, and their growth efficiency were around 16%, 18%, 17%, for the respective Batch Cultures ( 01,02,03). Of all the batch reactors 02 showed the greater growth efficiency. The variation of the TDS in the batch reactors is shown in figure 8. Figure 8: Variation of Total Dissolved Solids with respect to carbon dioxide sequestration from coal. Conclusion: From the study it is concluded that, the maximum biomass was obtained in the stage II and it was increased for about 18%, whereas in stage I the maximum biomass was increased only for 0.16%.so, carbondioxide sequestration with wastewater treatment can effectively produce the maximum biomass and this can be converted in to biofuel. This will further reduces the green house gases and thereby global warming will be avoided. For effective production of biomass and carbondioxide sequestration, microalgae can be grown in closed photobioreactors. This will increase the removal efficiency of carbondioxide. References: 1. Chien-Ya Kao, Sheng-Yi Chiu, Tzu-Ting Huang, Le Dai, Ling-Kang Hsu, Chih-Sheng Lin (2012), Ability of a mutant strain of the microalga Chlorella sp. to capture carbon dioxide for biogas upgrading, Appl.Energy, 93, Clarens.A.F., Resurrection. E.P., White. M.A., Closi.L.M., Environmental life cycle comparison of algae to other bioenergy feedstock. Environmental Science and Technology 44, Gonzalez, C., Marciniak, J., Villaverde, S., Garcia-Encina, P.A., Munoz, R., Microalgae-based processes for the biodegradation of pretreated piggery wastewaters. Applied Microbiology and Biotechnology 80,

10 Gokulan Ravindiran et al /Int.J. ChemTech Res.2014,6(1),pp Kanhaiya Kumar, Debabrata Das, (2012), Growth characteristics of Chlorella sorokiniana in airlift and bubble column photobioreactors, Bioresour. Technol, 116, Kumar. M.S., Zhihong. H.M., Sandy.K.W., Influence of nutrient loads, feeding frequency and inoculum source on growth of Chlorella vulgaris in digested piggery effluent culture medium. Bioresource Technology 101, Lardon, L., Helias, A., Sialve, B., Steyer, J.P., Bernard, O., Life cycle assessment and biodiesel production from microalgae. Environmental Science and Technology, 43, Mulbry, W., Kondrad, S., Buyer, J., Treatment of dairy and swine manure effluents using freshwater algae: fatty acid content and composition of algal biomass at different manure loading rates. Journal of Applied Phycology 20, Yang, J., Xu, M., Hu, Q., Sommerfeld, M., Chen, Y., Life-cycle analysis on bio-diesel production from microalgae: water footprint and nutrients balance. Bioresource Technology 102, Zhou, W., Min, Min, Li, Yecong, Hu, Bing, Ma, Xiaochen, Cheng, Yanling, Liu, Yuhuan, Chen, Paul, Ruan, Roger, A hetero-photoautotrophic two-stage cultivation process to improve wastewater nutrient removal and enhance algal lipid accumulation. Bioresource Technology 110, *****