Phyco-Remediation of Sugar Mill Effluent using Chlorella Vulgaris

Phyco-Remediation of Sugar Mill Effluent using Chlorella Vulgaris

Amol B. Deshmane1*, Sandip Jagadale1 and Virdhaval M. Nalavade2, 1Department of Environmental Sciences, Vasantdada Sugar Institute, Manjari (Bk), Pune, Maharashtra, 412307 India

2Department of Biotechnology, Yashvantrao Chavan Institute of Science, Satara, Maharashtra, 415001 India

Abstract:- Sugar is second largest agro industry in India. Thus, its importance is immense from economics point of view. However, the industry needs environment friendly and sustainable effluent treatment technologies considering the water and energy situations at global level. In the present experiment, alga Chlorella was experimented to treat sugar mill effluent (SME). Chemical oxygen demand (COD) of approx 6000 mg/L of SME was successfully reduced by >80% in the experiment with 144 h (6 days) of retention period. Produced algal biomass showed calorific value of approx 3,000 cal/g i.e. the treatment technology can produce energy and thus, important in near future for achieving sustainability.

Key words: Phyco-remediation, sugar mill effluent, Chlorella

1. INTRODUCTION

   Being agro-based industry, the sugar mills play an important role in the economic development of rural India. Its significance enhanced due to ethanol blended petrol programme initiated by the Government of India. However, sugar industry produces sizable amount of wastewater. According to the prevailing norms/guidelines, the industry produces 100 L of effluent and 100 L of spray pond overflow wastewater per ton of sugar cane crushed. The effluents contain a high amount of organic pollutants that contributes to chemical oxygen demand (COD. Thus, if effluent discharged untreated or partially treated outside the mill premises, it likely to cause pollution in recipient ecosystem i.e. aquatic and/or terrestrial. The physico-chemical characteristics of the receiving aquatic bodies likely to get altered due to the effluent. Similarly, aquatic flora and fauna gets affected in such situation.

2. SUGAR INDUSTRY AND WASTEWATER

   Wastewater with varying levels of pollution load is generated at different stages of sugar production. Pollution load is mainly observed due to oil, grease, sugar/juiceentrainment, bagasse or dust, floor washing and acids/bases or chemicals used for the processes. SME shows a chemical oxygen demand in the range of 1,500 to 5,000 mg/L. This load may increase due to operational issues of individual factory. This is mainly due to organic pollutants. Therefore, SME, if discharge untreated could deteriorate the water quality of receiving bodies and/or affect the soil and associate terrestrial ecosystem. It may cause an impact of various a magnitude on animals who consumes it. Wastewater from sugar industry is having BOD in the range of 1,000- 1,500mg/l, could rapidly deplete available oxygen, endangering aquatic life. Considering this and due to legal enforcement sugar factories have installed effluent treatment plants (ETPs). These plants are mainly based on activated sludge process. Several issues have been observed in treating SME through these conventional ETP. Some of them are

   • Inadequate & unskilled manpower: Usually ETP is operated by unskilled labor. Often, labor is seasonal or works on daily wage basis; Sometimes, supervising person is having low knowledge of ETP operation. Ultimately, the end result is ETP not serving its purpose.

   • Consumption of higher energy: Considerable amount of energy is spent on pumping activities as well as artificial aeration activity. Floating or sub-merged aerator are used for the said purpose.

   • Consumption of chemicals, improper operation of ETP, frequently changing hydrolique loads, etc. are other prime reasons for the search of an alternative treatment for SME.

   The research team has already worked on the SME treatment using algae. Algae is immerging as a biofuel source, its cultivation cost can be controlled by cultivating it using wastewater and nutrients. EPA has specifically identified conventional wastewater treatment plants as major contributors to greenhouse gases. Algae based wastewater treatment also releases carbon dioxide (CO2) but the algae consume more CO2 while growing than that is being released by the plant, this makes the entire system carbon negative, so this research could give a new idea of a more modern concept or approach to sugar industries for better management of their wastewater.

   In algal wastewater treatment facilities, the main objective of sludge management is to maximize algal biomass production. The resulting sludge with algal biomass is energy rich which can be further processed to make biofuel or other valuable products such as fertilizers.

   In short, the present work was planned with an objective to study the effectiveness of the treatment for reducing COD/BOD of SME as well as estimate the Chlorella biomass production using SME.

3. MATERIALS AND METHOD

   Set A: Experiment

   Set B: Control for treatment

   Set C: Control for algal growth

   Set A: Experiment

   Set B: Control for treatment

   Set C: Control for algal growth

   SME 2000 ml

   SME 2000 ml

   Fresh water 2000 ml

   SME 2000 ml

   SME 2000 ml

   Fresh water 2000 ml

   Chlorella culture 200 ml

   Distilled water 200 ml

   Chlorella culture 200 ml

   Chlorella culture 200 ml

   Distilled water 200 ml

   Chlorella culture 200 ml

   Content stirred continuously

   @ 100 RPM

   Content stirred continuously

   @ 100 RPM

   Samples drawn at 24 h interval for monitoring the change; Total treatment time 144 h

   Figure 1: Schematic of experimental setup

   SME was collected from Shreenath Mhaskoba Sugar Limited, Pune. Raw effluent (Untreated effluent) was collected from the surface of holding pond in 20 L bucket & transferred to clean plastic can of 35 L. Then collected effluent was stored in cold storage till the day of analysis. It was brought to ambient temperature before commencing any testing & experiments with it. It is used as per requirement of the experiment.

   A culture of Chlorella collected and isolated from natural fresh waterbody near to the laboratory. The same was maintained at Department of Environment science of Vasantdada Sugar Institute, Pune.

   Set A

   Set B

   Set C

   Figure 2: a) Experimental setup at zero hour i.e. initial b) Set A, B and C after 144 h treatment

   The experimental set up is illustrated in the figure 1. Explained here in short, 2,000 ml SME was taken in a container and in which 200 ml of Chlorella cells were added. The cell density of the Chlorella maintained by measuring its optical density at 660 nm and maintained at 0.613 ±0.050. This mixture was poured in 1.5 L flat bottom jars (as shown in figure 2). Set B and Set C prepared as per the figure 1 and content transferred to the jars. The content of the jar stirred continuously at 100 RPM ±10. During the experiment Laboratory temperature was observed 330C± 3 during day time and 270C ± 2 during night. Artificial light of 1000 lux provided for 12 h every day during experimental period.

   8

   7.5

   7

   6.5

   6

   5.5

   5

   4.5

   4

   Change in pH

   Initial Set A Set B

   7000

   6000

   COD (mg/L)

   COD (mg/L)

   5000

   4000

   3000

   2000

   1000

   0

   Change in COD

   Initial Set A Set B

   7000

   dry weight (mg/L)

   dry weight (mg/L)

   6000

   5000

   4000

   3000

   2000

   1000

   0

   Dry Biomass

   <>Initial Set A Set C

   Figure 3: Change in the a) pH of SME b) COD and c) dry biomass of Chlorella after 144 h treatment

   Figure 4: Dry biomass generated during the experiment

   	Gross Calorific value (cal/g)
   Chlorella dry biomass	3,356± 153
   Dry sludge of SME including Chlorella	3,896 ± 93

4. DISCUSSION

The major achievement of the experiment is efficient COD reduction without any expensive chemicals. Overall, COD reduction of > 80% achieved in 144 h (i.e. 6 days) treatment. This is very similar to the observation reported by Goncalves et al. (2017), who reported pollutant removal ability of algae as 214 dHRT. He et al., (2013) and Wang et al. (2015) reported that algae can grow well only in wastewater having lower COD (below 5,000 mg L_1). But, the present study showed that, Chlorella can survive and treat industrial effluent having COD of > 5,000 mg/L. This treatment time may get reduced if the experiment carried out in the actual sun light (Deshmane et al. 2022).

The second objective of the experiment focused on bio-energy from the treatment process. If, the dry sludge (95%+ dry) from the treatment process used as a fuel it has excellent calorific value. On an average 5 to 6 g of sludge generated per litre of SME. A sugar mill of 5,000 ton per day crushing capacity produces 500 m3 of SME. Thus, 2.5 to 3 tons of sludge anticipated which is sizable. In short, the results indicate that, SME is having good potential to serve as a growth medium for algae. Dry algal biomass can be used for the feedstock to produce bio-energy.

REFERENCES

1. Deshmane A.B., Jadhav V.P., Ghole V.S. 2022. Sugar mill effluent treatment using fixed film algal photo-bioreactor and reuse of treated water. International Journal of Scientific and Research Publications 12(01) 518-527.

2. Gonçalves Ana L, José C.M. Pires, Manuel Simões, 2017. A review on the use of microalgal consortia for wastewater treatment. Algal Research, Volume 24, Part B, 403-415.

3. He, P.J., Mao, B., Shen, C.M., Shao, L.M., Lee, D.J., Chang, J.S., 2013. Cultivation of Chlorella vulgaris on wastewater containing high levels of ammonia for biodiesel production. Bioresour. Technol. 129, 177181.

4. Wang, Y., Guo, W., Yen, H.W., Ho, S.H., Lo, Y.C., Cheng, C.L., Ren, N., Chang, J.S., 2015. Cultivation of Chlorella vulgaris JSC-6 with swine wastewater for simultaneous nutrient/COD removal and carbohydrate production. Bioresour. Technol. 198, 619625.