Abstract

Water pollution is a one of the major environmental issue that the world is facing nowadays. The untreated effluent as well as the chemically treated effluent both results in pollutions. These toxic contaminants directly and indirectly affect the flora and fauna of the ecosystem. The solution for such a drastic environmental issue lies within the cells of one such cosmopolitan plant group namely “Algae”. These are certain algal species which have the inhibit capacity to utilize some of the most threatening environmental contaminants such as nitrogenous compounds, ammonia, phosphates and some of the metal ions so on. Hence, treating the effluent with algae would be an eco-friendly method to reduce pollution. Phycoremediation of effluent using algae is a novel green-technique when applied to aqueous pollution. The present investigation included the preliminary screening of microalgae potentials for their tolerance and growth in paint effluent from an electroplating industry which include the native microalgae isolated from the effluent treatment plant (ETP). The microalgae, such as Chlamydomonas pertusa, Dactylococcopsis raphioides and Chlorococcum humicolo were selected and employed in the treatment of electroplating paint effluent an individually and also as mixed algal group. The physico-chemical parameters were analyzed. The individual culture and the mixed algal culture both could effectively reduce TDS (Total Dissolved Solid), TSS (Total Suspended Solid), free ammonia, calcium, sodium, nitrate and phosphate. Chlorococcum humicolo had a significant remedial level of Turbidity (20.51%), Calcium (95.76%), Sodium (8.33%), Free ammonia (62.96%), Phosphate (71.29%) and Total Kjeldhal Nitrogen (48.23%) treated with paint effluent of electroplating industry among the microalgae. Thus, Chlorococcum humicolo could be selected for further field pilot scaling up study. Phycoremediation is a cost-effective, efficient and a sustainable technology for future clean earth.

1. Introduction

The environmental contamination is increasing day-by-day due to the various anthropogenic activities. The different kinds of toxic pollutants such as organic/inorganic chemicals, dyes, heavy metals, pesticides etc. enter in to the environment from different sources such as municipal, agricultural and industries ¹. Algae are a group of photosynthetic organisms which can thrive even in harsh environment. They have a high potential to eradicate pollutants from the effluents of industries and urban zones ². The prospective applications of phycoremediation have prompted laboratories to reinforce the improvement of algal based green technologies for healthier manipulation of their bioremediation potential and by-product generation capacity ³. Microalgae based biorefinery together with effluent treatment method also enhances the economical biomass production ⁴. The phycoremediation mechanism of heavy metals in wastewater by using probable microalgae and their improved products was analyzed ⁵. Algal cultivation during wastewater management uptakes nutrients and assimilates CO₂ their by increasing the production of algal biomass ⁶. The effectiveness of phycoremediation using microalgae for eliminating nutrients and heavy metals from the wastewater have been proved ⁷. The domestic sewage wastewater treatment and biogas produced with microalgae based technology is cost-effective and eco-friendly ⁸. Microalgae are very effective at eliminating various nutrients from municipal wastewater ⁹. It had proven effective in eliminating heavy metals from the tannery effluent with the highest level ¹⁰. The effective elimination of diazinon from the aqueous segment by a freshwater microalga, Chlorella vulgaris was done ¹¹. The usage of microalgae to eliminate nutrient from the municipal wastewater treatment has shown recent enhancements in the considerate of removal mechanisms and progress of both the suspended and non-suspended methods. This nutrient directly and indirectly utilized is proportional to the rate growth and biomass concentration ¹². Microalgae are representing an outstanding model organism and could be used for various heavy metals and metalloids removals ¹³. The use of potential cyanobacteria for the removal of various heavy metals and nutrients from wastewater is the gaining curiosity due to its cost-effective process and being ecologically benevolent ¹⁴.

The efficient removal of organic micronutrients from the urban wastewater treatment was studied in two pilot high-rate algal ponds using microalgae. This efficient removal reached from negligible to more than 90% depending on the compound of pollutant ¹⁵. The effectiveness for the bioremediation of municipal wastewater was assessed by determining the COD (Chemical Oxygen Demand), total phosphorous content and total nitrogen at the end of each batch cultivation ¹⁶. Mixotrophic microalgae biofilm established an applicability of assimilating this innovative cultivation method with wastewater for maximum efficacy ¹⁷. Microalgae cultivation as an alternate method for treatment of anaerobic digestion effluent was surveyed using two microalgae species, Chlorella protothecoids and Chlorella vulgaris. Both algal species have effectively removed ammonia and nitrate from the four digesters treated effluents under different operated conditions ¹⁸. The exclusive pilot-scale photobioreactor structure are highly scalable and provided an abundant opportunity for the Chlorella sp. biomass production coupled with wastewater treatment ¹⁹. The performance of two microalgae, Chlorella vulgaris and Pseudochlorella pringsheimii was assessed for the phycoremediation of combined sewage and tannery effluent under the different dilutions. The result showed significant reduction in contaminants such as ammonia, phosphate, chemical oxygen demand and total chromium in the effluent for both the algal species ²⁰. The proficiency of the native algal strains, Chlorella sp. and Scenedesmus sp. in the integrated management system to treat the effluent from palm oil mill industry and capture to CO₂ from the flue gas was analyzed ²¹. The microalga, Chlorella sp. was cultivated in the batch photobioreactor (PBR) with various nitrogen sources to determine the biomass retention time (BRT) on nutrient uptake and biomass productivity showed that the algal biomass yield increase as the BRT reduced, leading to an increase in pollutant elimination rates very effectively ²². The high rate algal pond (HRAP) methods have provided opportunities for low-cost wastewater treatment and energy retrieval from the wastewaters and waste solids, as well as biofuel production after harvesting algal biomass ²³. This method is beneficial perception to help future improvement of effluent and commercially feasible technology for microalgae based heavy metals and nutrients removal using bioremediation ²⁴.

Each type of industry produces its own kind of chemical contaminants in its effluent. There are specific algal species which individually react with this toxic pollutant. This research basically concentrates finding the algal species which is more efficient in treating paint effluent from an electroplating industry. In this view, the present investigation comprises the preliminary screening of microalgal potentiality for their tolerance and growth in the paint effluent from an electroplating industry which include the native microalgae isolated from the effluent treatment plant (ETP).

2. Materials and Methods

The experiment was studied in the PG and Research Department of Botany, Ramakrishna Mission Vivekananda College (Autonomous), Chennai – 600004, Tamil Nadu, India. The collected and isolated potentials microalgal species from effluent treatment plant (ETP) of electroplating industry were grown in the culture medium of Bold Basal Medium (1965), Central Food Technological Research Institute (1954) and raw effluent in the laboratory. The cultures were grown at 24 ± 1°C in a thermo-statically controlled environmental chamber illuminated with cool white fluorescent lamps (Philips 40w, cool daylight, 6500k) at an intensity of 2000 LUX in a 12/12 hours light/dark cycle. The feasibility study of microalgae potentials for their tolerance and growth in the paint effluent from an electroplating industry was investigated. The various parameters were analyzed after phycoremediation of paint effluent. Growth was measured by counting cells using a Heamocytometer (Neubauer, improved) and dry weight bases, pH was measured using digital pH meter (Elico LI 120), conductivity using digital conductivity meter (Equiptronics EQ - 660A) and estimation of physic-chemical parameters by American Public Health Association (2000) methods respectively.

3. Results and Discussion

The proliferation of industries to meet the basic needs of mankind increases the problem of pollution. The biological treatment is an important and vital part of any wastewater management plant that treats effluents from whichever municipality or industry having an organic, inorganic impurities and heavy metals ²⁵. The biotechnology of microalgae has expanded attractiveness due to the growing essential for novel environment green-technologies and the improvement of advanced mass production ²⁶. Microalgae based heavy metals bioremediation is reflected as a potential solution for determining present environmental glitches ²⁷. The algal based sewage treatment plant recycle 67.65 million liters per day of domestic wastewater and have recognize the role of algae in the treatment of sewage ²⁸. Phycoremediation using the native microalgae from the natural sources provided a capable process for bifenthrin elimination with the predominant algal species Parachlorella kessleri facilitating the biodegradation and biosorption process ²⁹. The best reduction was achieved by the microalga Chlorella sp. with municipal wastewater and triggered sludge treatment ¹⁶. The influence of calcium peroxide pretreatment on sulfonamide antibiotic remediation by microalga, Chlorella sp. was done ³⁰. Chlorella vulgaris has an extraordinary potential to endure as well as uptake nutrients and heavy metals from tannery wastewater treatment ³¹. The cyanobacteria, Chrococcus turgidus can be used in the mixed wastewater including domestic, textile and milk industrial bioremediation process which was very significant for resource management and sustainable environment ³². The outdoor cultivation of two microalgal species, Chlorella sp. and Scenedesmus sp. in the raw anaerobically digested abattoir effluent (ADAE) which were exposed to both continuous (24 hours) and daytime only (12 hours) paddle wheel mixing method was done. The microalga, Scenedesmus sp. established higher biomass productivity and nutrient elimination efficiency in the ADAE when compared to the Chlorella sp., with the continuously mixed cultures being most resourceful ³³.

The potential application of microalga, Chlorella vulgaris for phycoremediation of textile wastewater (TW) treatment was examined using four batches of cultures in high-rate algal ponds (HRAP) containing dye effluent. The biomass achieved ranged from 0.17 to 2.26mg chlorophyll a/L while colour removal range from 41.8% to 50%. There was also reduction of ammonia (44.4-45.1%), phosphate (33.1-33.3%) and chemical oxygen demand (38.3-62.3%) in the treated textile wastewater ³⁴. The acid-producing effluent was recycled three times utilization by heterotrophic potential microalga, Chlorella sorokiniana, the significant removal rates of chemical oxygen demand of 74.44%, total nitrogen of 88.05%, ammonia nitrogen of 79.08% and total phosphorus 82.69% was estimated ³⁵. The efficiency of Scenedesmus sp. to remediate heavy metals from the wet market wastewater highest level 93.06% of cadmium, 92.40% of iron, 92.40% of zinc and 91.50% of chromium respectively was analyzed ⁷. The Zinc captivation by biomass of Spirulina platensis has been used to remove many pollutants by absorption in electroplating industrial effluent ³⁶. Potentially adverse effects of microalga, Chlorella vulgaris in the removal of sulfonamides and heavy metal of copper are frequently detected together in livestock wastewater treatment ³⁷. Chlorella vulgaris potentially remediated 98.63% of petroleum hydrocarbons and COD of 75% from crude oil exploration wastewater treatment for safe disposal ³⁸. An innovative system that associate centrate wastewater management and microalgae cultivation was established and tested under low light situations with different harvesting rates and CO₂ inoculation levels by using a nearby screened algal strain of Chlorella sp. The system can yield 34.6 g^.m^-2day^-1 TSS (total suspended solids) and 17.7±4.2 g^.m^-2day^-1 VSS (volatile suspended solids) and removed 70% COD (chemical oxygen demand), 61% TKN (total Kjeldahl nitrogen), and 61% STP (soluble total phosphorus) compared to other methods ¹⁹. The flagellate unicellular organism, Euglena proxima isolated from the tannery industrial effluent showed the tolerance against chromium (Cr⁶⁺) and lead (Pb²⁺). Chromium and lead treating abilities of Euglena proxima were operated for its potential usage as bioremediator of wastewater. Euglena proxima could also remove heavy metals such as Cr⁶⁺ of 88% and Pb²⁺ of 84% very effectively. The uptake ability of heavy metals by Euglena proxima can be demoralized for metal decontamination and environmental clean-up processes ³⁹. The feasibility of cultivated microalgae, Chlorella sp. and Scenedesmus sp. to succeed in the tannery effluent was analyzed. Both the algae could effectively remove heavy metals such as chromium, copper, lead and zinc with the highest rates ¹⁰. The dairy effluent treatment by immobilized algae, Euglena gracilis and Chlorella pyrenoidosa significantly removed ammonia and phosphate in both open and closed methods ⁴⁰.

The potential of cyanobacteria, Lyngbya majuscula biomass to remove Cu(II) of 99.15% from simulated wastewater treatment was done ⁴¹. The bioaccumulation and biosorption in the microalga, Arthrospira platensis were effective approaches for the removal of various heavy metals from Yamuna river water treatment ⁴². Three microalgal species were investigated for their capability to accumulated metal ions. The microalgae, Chlorella sp., Scenedesmus sp., and Selenastrum sp. were found proficient in accruing metals such as copper, chromium and lead with 67% to 98% efficiency ⁴³. Anabaena variablis cultivation in waste utilized medium have revealed its excellent phycoremediation ability ⁴⁴. The microalga Scenedesmus obliqus used in brewery wastewater treatment and biomass production showed, a higher reduction chemical oxygen demand of 57.5% and total nitrogen of 20.8% respectively ⁴⁵. Synechocystis sp., which grew fast and flourished in wastewater with phosphate and ammonium showed removal efficiencies of 97.5% and 99.4% ⁴⁶. The potentials of microalgae Scenedesmus quadricauda and Chlorella vulgaris were effectively involved for wastewater treatment and removal of heavy metals. The microalgae contaminants removal efficiency reached to BOD (92.7%), COD (87.5%) and 100% for TN and TP. The removal of heavy metals by microalgae reached to Cu (98.8%), Zn (90.4%), Cd (83.9%), Ni (75.7%), Co (99.8%), Fe (99.7%) and Pb (99.5%) in the similar way ⁴⁷. The significant removal of heavy metals, such as Zinc and Copper by green microalgae Monoraphidium pusillum and Desmodesmus communis, when applied to the wastewater treatment was proved ⁴⁸. The most effective treatment of municipal wastewater by alga, Muriellopsis sp., was pilot-scale phycoremediation investigation (800-L raceway pond), which removed 93% of phosphorus and 84% of nitrogen and other chemical compounds after 4 days of treatment of wastewater ⁴⁹.

The paint effluent was collected from electroplating industry situated at Chennai. The effluent is generated from coating of wheels, this effluent which is alkaline, contains various chemicals, especially high Total Dissolved Solids (TDS), calcium chloride and heavy metals.

The feasibility study was deals with the preliminary screening of potentials microalgae for their tolerance and growth in the paint effluent from an electroplating industry which include the native microalgae isolated from the effluent treatment plant (ETP) as well as the culture collection of microalgal species from the Department of Botany, Ramakrishna Mission Vivekananda College, Chennai, Tamil Nadu, India. The algae employed for the study were as follows; The microalgae, Chlamydomonas pertusa, Dactylococcopsis raphioides, Desmococcus olivaceus, Chlorococcum humicolo, Chroococcus turgidus, Chlorella vulgaris, Scenedesmus dimorphus and Scenedesmus incrassatulus were inoculated in to raw effluent and effluent amended with CFTRI and BBM nutrients and incubated for 7 days. Growth rate was studied and the results were tabulated based on the difference between the initial and final cells during log phase of individual algae.

Chlamydomonas pertusa, Dactylococcopsis raphioides, Chlorococcum humicolo, Chlorella vulgaris, Desmococcus olivaceus and Scenedesmus dimorphus showed growth rate of 0.3060, 0.5378, 0.4525,0.3018, 0.2170 and 0.2300 divisions/day respectively. Scenedesmus incrassatulus and Chroococcus turgidus did not grow in the effluent. When the effluent was supplemented with BBM, Chlorococcum humicolo showed maximum growth rate (0.4265) followed by Chlamydomonas pertusa (0.4087 divisions/day). Dactylococcopsis raphioides showed 0.3281 divisions/day. Scenedesmus dimorphus exhibited a poor growth rate (0.0093 divisions/day). Scenedesmus incrassulatus did not grow in the BBM supplemented effluent. In the effluent supplemented with CFTRI nutrients, Chlorococcum humicolo showed maximum growth rate (0.1520 divisions/day). Dactylococcopsis raphioides showed growth rate of 0.0120, Chlamydomonas pertusa showed 0.0406 divisions/day. The results are given in Figure 1. Paint effluent supported the growth of micro algae very well. So further experiments were conducted with paint effluent.

Actively grown cells of Chlamydomonas pertusa, Dactylococcopsis raphioides, Cholorococcum humicolo and a mixture of all these algae were centrifuged and the washed pellet was resuspended in 2 litres of the effluent in a conical flask bioreactor and incubated in the culture rack for 10 days. The algae survived well when inoculated individually, whereas in the case of algal mixture, Chlorococcum humicolo was found to be dominating with the growth rate of 0.2943 divisions/day. The effluent sample was analyzed for physico-chemical parameters before and after treatment and the results are shown in Table 1 – Table 3 and Figure 2 – Figure 9.

Phycoremediation could effectively reduce TDS, TSS, free ammonia, nitrate and phosphate very effectively all the individual microalga including mixed algal culture. The microalgae, such as Chlorococcum humicolo was maximum reduce the Turbidity (20.51%), Calcium (95.76%), Sodium (8.33%), Free ammonia (62.96%), Phosphate (71.29%) and Total Kjeldhal Nitrogen (48.23%); followed by the Chlamydomonas pertusa was reduce the Total Solids (10.68%), Total Suspended Solids (60%) and Nitrate (21.42%) and Dactylococcopsis raphioides was reduce the Potassium (25%) respectively to treated with paint effluent of electroplating industry. The significant reduction of Total Dissolved Solids (5.47%), Total Hardness (5.66%), Calcium (5.76%), Magnesium (5.26%), Potassium (25%), Nitrate (95.48%), Flouride (20.16%), Chloride (7.13%) and Silica (24.93%) respectively when applied to treated with electroplating industrial paint effluent. Chlorococcum humicolo was remediated significant level among the other microalgae. The potential microalga, Chlorococcum humicolo could be selected for further field pilot scaling up this technology to manage paint effluent of electroplating industry.

4. Conclusion

Phycoremediation of effluent using algae is a novel technique when applied to aqueous contamination. The present investigation dealt with the preliminary screening of microalgal species to analyses their potential to tolerate and grew in the paint effluent from an electroplating industry. The microalgae, Chlamydomonas pertusa, Dactylococcopsis raphioides and Chlorococcum humicolo were selected and employed in the treatment of electroplating paint effluent. The physico-chemical parameters were analyzed. Phycoremediation could effectively reduce TDS, TSS, free ammonia, calcium, sodium, nitrate and phosphate in the algal treated paint effluent. Among the three microalgae, Chlorococcum humicolo showed that significant level of remediation. The potential alga, Chlorococcum humicolo could thus be selected for further field pilot scaling up technology to manage paint effluent of electroplating industry. Phycoremediation has them proved itself as a cost-effective and eco-friendly technology.

Acknowledgments

The author are very much thankful to the authorities of Electroplating Industry, Chennai to provide the effluent samples for academic research work, the HOD, PG and Research Department of Botany, the Principal and Secretary, Ramakrishna Mission Vivekananda College (Autonomous), Chennai, Tamil Nadu, India for providing laboratory facilities to complete the research work.

References