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Phycoremediation efficiency of three micro algae Chlorella vulgaris, Synechocystis salina and Geloeocapsa gelatiosa



An attempt was made to reduce the nutrient load of industrially polluted water using micro algae Chlorella vulgaris, Synechocystis salina and Gloeocapsa gelatinosa. The polluted water sample after sterilization was treated with these algae and the improvement of water quality was assessed in regular intervals. Uptake of nutrients like phosphate, nitrate and nitrite by the algae and the amount of dissolved oxygen in the water sample and the change in pH has been studied. All these parameters had been studied at a regular interval of 5 days for a period of 25 days. From the regular analysis it was found that all these algae were efficient in reducing the nutrient load of the water sample. The removal efficiency was very high. Gloeocapsa gelatinosa showed more efficiency than Chlorella vulgaris and Synechocystis salina in phycoremediation.
* Dominic VJ, Soumya Murali and Nisha MC.
An attempt was made to reduce the nutrient load of industrially polluted wa-
ter using micro algae Chlorella vulgaris, Synechocystis salina and Gloeocapsa
gelatinosa. The polluted water sample after sterilization was treated with these algae
and the improvement of water quality was assessed in regular intervals. Uptake of
nutrients like phosphate, nitrate and nitrite by the algae and the amount of dissolved
oxygen in the water sample and the change in pH has been studied. All these param-
eters had been studied at a regular interval of 5 days for a period of 25 days. From the
regular analysis it was found that all these algae were efficient in reducing the nutrient
load of the water sample. The removal efficiency was very high. Gloeocapsa
gelatinosa showed more efficiency than Chlorella vulgaris and Synechocystis salina
in phycoremediation.
Keywords:Phycoremediation, Chlorella, Synechocystis, Gloeocapsa, water pollution,
periyar river.
Phycoremediation is the process of employing algae for improving water quality.
Algae can fix carbon dioxide by photosynthesis and remove excess nutrients effec-
tively at minimal cost. In addition, photosynthetically produced oxygen can relieve
biological oxygen demand (BOD) in the waste water. Micro algae are superior in
remediation processes as a wide range of toxic and other wastes can be treated with
algae and they are non pathogenic. The risk of accidental release of pollutants into the
atmosphere causing health safety and environmental problems are avoided when al-
gae are employed for remediation. Algae utilize the wastes as nutritional sources and
enzymatically degrade the pollutants. The xenobiotics and heavy metals are known to
be detoxified/ transformed/or volatilized by algal metabolism. They have the ability to
take up various kinds of nutrients like nitrogen and phosphorus. (Muthukumaran et al.
2005). They can utilize various organic compounds containing nitrogen and phospho-
rus from their carbon sources. Many researchers have studied micro algae as pos-
Department of Botany, Centre for PG studies and Research, Sacred Heart College,
Thevara, Ernakulam (Dt.), Kerala.
* Corresponding author:
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sible solution for environmental problems (Craggs et al. 1997, Lau et al. 1994). Algal
growth can keep the water clean and make natural waters more suitable for human
The choice of micro algae to be used in wastewater treatment is determined
by their robustness against wastewater and by their efficiency to grow in and to take
up nutrients from wastewater (Olguin, 2003). In well oxygenated high rate ponds,
climax cultures that are not readily grazed consist mainly of coccoid green algae
forms (Oswald, 1998). Some algae which are generally used for the waste water
treatment are Chlorella, Scenedesmus, Synechoccystis, Gloeocapsa, Chroococcus,
Anabaena, Lyngbya, Oscillatoria, Spirulina and the like
Pollution is a common feature in almost all rivers and lakes in Kerala because
of organic and industrial wastes. 'Periyar' river is one among the most polluted rivers
in Kerala. At the industrial area of Eloor, situated at the banks of Periyar, about 247
chemical industries are located. This is one of the world's "top toxic hot spots" and
ranked No.35 in the world's worst polluted places in a study conducted by Greenpeace
International. The large scale industrialization and consequent effluent discharge have
made this part of the river almost lifeless or dead.
The present study aimed at a comparative study of phycoremediation effi-
ciency of Chlorella vulgaris (Chlorophyceae), Synechocystis salina (Cyanophyceae)
and Gloeocapsa gelatinosa (Cyanophyceae) using water samples collected from a
highly polluted region of 'Periyar' river at Eloor zone.
The micro algae Chlorella vulgaris, Synechocystis salina and Gloeocapsa
gelatinosa were collected from Department of Marine Biology, Cochin University of
Science and Technology and employed for a detailed investigation on phycoremediation
and removal of nutrients from water sample.
Phycoremediation studies were carried out in industrially polluted waters col-
lected from Periyar near Eloor region which is highly polluted due to the effluents
discharged from the nearby industries.
The algal samples were cultured in proper culture media. Chlorella vulgaris
was cultured in Walne's medium and Synechocystis salina and Gloeocapsa
gelatinosa were cultured in Allen and Nelson medium. The algal culture was incu-
bated at 23±1°C temperature and 2000 lux light. A 16:8 hour light/ dark cycle was
provided in order to obtain synchronous culture.
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Water sample collected from industrially polluted region was analyzed for
different physio chemical parameters. (Gupta, 2004). The parameters under study
were pH, nitrate, nitrite, phosphate and dissolved oxygen.
Separate water samples were inoculated with 5% Chlorella vulgaris, 5%
Synechocystis salina and 5% Gloeocapsa gelatinosa. Water samples without al-
gae were kept as control.
The water samples which were incubated with algae were analyzed for these
parameters at an interval of five days for a period of 25 days. The bioremediation
efficiency of the algae was calculated [(C0-C25)/C1] x 100 after the 25 days of treat-
Preliminary analysis of the water sample revealed the pH of the water sample
as 6, presence of 2.8µmol/l phosphate, 1.4µmol/l nitrate and 0.2µmol/l nitrite. Dis-
solved Oxygen of the water sample was 2.3mg/l.
Change in the water quality after treatment with algae was checked in an
interval of 5days for a period of 25days. pH of the water sample treated with Chlo-
rella vulgaris showed a drift towards alkalinity. pH has been changed from 6.0 to 8.1
(Table 1). pH was drifted from 6 to 8 in the water sample treated with Synechocystis
salina (Table 2). pH has been changed from 6.0 to 7.9 in the water sample treated
with Gloeocapsa gelatinosa (Table 3; Fig. 1).
The amount of phosphate in the water sample treated with Chlorella vul-
garis reduced from 4.6µmol/l to 1.4µmol/l (Table 1). Phosphate uptake efficiency of
the algae is 69.23% (Table 4). There was 64.52% reduction in the phosphate content
in the water sample treated with Synechocystis salina (Table 4). The concentration
of phosphate has been decreased from 3.1µmol/l to 1.1µmol/l (Table 2). The concen-
tration of phosphate in the water sample treated with Gloeocapsa gelatinosa has
been decreased from 3.1µmol/l to 0.8µmol/l (Table 3; Fig. 1).
2.5µmol/l of nitrate had been reduced to0.4µmol/l in the water sample treated
with Chlorella vulgaris (Table 1). 84% reduction in the nitrate content has been noted.
(Table 4). 82.5% decrease in the nitrate content has been observed in the water
sample treated with Synechocystis salina (Table 4). The concentration of nitrate has
been reduced from 2µmol/l to 0.35µmol/l (Table 2). The concentration of nitrate in the
water sample treated with Gloeocapsa gelatinosa has been reduced from 2µmol/l to
0.4µmol/l (Table 3; Fig. 1).
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Nitrite in the water sample had been completely absorbed by the micro algae
Chlorella vulgaris and Gloeocapsa gelatinosa whereas in the control there was
only a slight reduction. (Table 1, Table 3). 96.23% reduction in the nitrate content has
been observed in water sample treated with Synechocystis salina (Table 2). The
concentration of nitrite has been reduced from 5.3µmol/l to 0.2µmol/l (Table 2; Fig. 1).
The Dissolved Oxygen of the water sample treated with Chlorella vulgaris
has been increased from 2.3mg/l to 8mg/l (Table 1). Synechocystis salina showed an
increase in the Dissolved Oxygen from 2.3mg/l to 6.4mg/l (Table 2). Gloeocapsa
gelatinosa showed an increase in the Dissolved Oxygen from 2.3mg/l to 5.9mg/l
(Table 3; Fig.5).
Table 1: Phycoremediation with Chlorella vulgaris in industrially polluted water
Table 2: Phycoremediation with Synechocystis salina in industrially polluted
Table 3: Phycoremediation with Gloeocapsa gelatinosa in industrially polluted
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Table 4. Bioremediation efficiency of Chlorella vulgaris, Synechocystis salina
and Gloeocapsa gelatinosa
Phycoremediation is a novel technique that uses algae to clean up polluted
water and soil. It takes advantage of the alga's natural ability to take up, accumulate
and degrade the constituents that are present in their growth environment. Algae
based waste water treatment systems offer more simple and economical technology
as compared to the other environmental protection systems. Photosynthesis can be
effectively exploited to generate oxygen from waste water remediation by algae. The
ability of micro algae Chlorella vulgaris, Synechocystis salina and Gloeocapsa
gelatinosa to reduce the nutrient load of polluted water sample collected from indus-
trially polluted region has been studied and compared.
Analysis of various physio-chemical parameters before and after treatment
revealed that the micro algae Chlorella vulgaris, Synechocystis salina and
Gloeocapsa gelatinosa could effectively improve water quality by removal of pollut-
ants. The studies on the nutrient uptake by these micro algae clearly reveal the effi-
ciency of algae to remove nutrients from polluted water bodies. All the three algae
showed high efficiency in the removal of nutrients.
pH of the water sample treated with Chlorella vulgaris showed a drastic change
of 35.79%. 32.61% pH change has been observed in the water sample treated with
Synechocystis salina. 31.19% change in the water sample treated with Gloeocapsa
gelatinosa was observed. The carbon dioxide produced by respiration of plants and
animals in water have the effect of lowering the pH. Carbon dioxide and bicarbonate
removed from the water by the photosynthetic process of aquatic plants raises the
pH. The same processes alter the dissolved oxygen content; oxygen drops during
respiration and decomposition; it rises with photosynthetic activity (Aarti et al. 2008).
Kotteswari et al. (2007) also reported a pH change from 5.62 to 9.82. Manoharan and
Subrahmanian (1992) have also reported a rise in the pH value up to 10th day of
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growth. 46.43% increase in the pH has been reported in diary waste water treated
with cyanobacteria. Vijayakumar et al (2005) reported increase in pH in the dye efflu-
ent treated with Oscillatoria sp. Aarti et al. (2008) reported the buffering effect of
Chroococcus turgidus in the sense the lower pH values were raised and the higher
pH values were reduced.
The specific use of cyanobacteria in the efficient removal of different forms
of combined nitrogen and phosphorus has also reported (Chan et al. 1979, Shi Jing et
al. 2007). In the present study when the polluted water sample was treated with
Chlorella vulgaris the phosphate content was reduced by 69.23%. 60% of the phos-
phate had been removed by Chlorella vulgaris within 10 days. Water sample treated
with Synechocystis salina showed a decrease by 64.52%. Gloeocapsa gelatinosa
showed a decrease by 75%. 52% reduction was seen in the 10th day. Kotteswari et al
(2007) reported 88.82% reduction in the phosphate content on 15th day. The capacity
of cyanobacteria to remove large amounts of phosphorus from waste waters was
demonstrated by several workers (Chan et al. 1979, Anandaraj et al. 2001). Tam and
Wong (1990) reported the removal of over 90% total phosphorus within 10days of
algal cultivation. 98% reduction in the phosphate level in the lake water treated with
Chroococcus turgidus have been reported by Aarti et al. in 2008. 95% reduction in the
phosphate level in the effluents of tannery and pharmaceutical industries treated with
Chroococcus turgidus has been reported (Vignesh et al. 2006).
The nitrate content of the water sample treated with Chlorella vulgaris showed
84% reduction while the water sample treated with Synechocystis salina showed
82.5 % reduction. 80.9% reduction in the nitrate content has been observed in the
water sample treated with Gloeocapsa gelatinosa. 52.8% of nitrate had been ab-
sorbed by Chlorella vulgaris within 5 days. 50% reduction in the nitrate content had
been seen in the water sample treated with Synechocystis salina within 5 days. 60%
nitrate has been absorbed by Gloeocapsa gelatinosa in 10 days. In the present study
when the polluted water sample was treated with Chlorella vulgaris and Gloeocapsa
gelatinosa the nitrite content was fully absorbed by the algae. They showed 100%
removal efficiency. Water sample treated with Synechocystis salina showed a decrease
by 96.23 %.
Dissolved Oxygen in the water sample treated with Chlorella vulgaris had
been found increasing by 247.83% and in water sample treated with Synechocystis
salina 178.26 % increase was noted. 152.9% increase in the water sample treated
with Gloeocapsa gelatinosa was observed. Respiration of animals and plants in the
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water body decreases the amount of dissolved oxygen in the water. It rises with the
photosynthetic activity of algae (Aarti et al. 2008).
Cyanobacteria are known to inhabit various aquatic polluted and heavily pol-
luted environments where they are widely distributed and dominate the micro floral
populations (Fogg 1987). They acquire natural resistance and selectivity against envi-
ronmental pollutants due to their presence in polluted systems while their viability and
metabolic activity are not affected by the decrease in the levels of the biodegradable
pollutants that may break down. Cyanobacteria have been used effectively as a low
cost method for remediating diary wastewater (Lincoln et al. 1996) dissolved inor-
ganic nutrients from fish farms (Duma et al. 1998) and nitrogen and phosphorus nutri-
ents (De Bashan et al. 2004, Phang et al. 2000). They were also reported as efficient
agents for the assimilation of organic matter from contaminated media as well as
transformation and removal of heavy metals (Ash and Jenkins 2006).
Stimulating the natural process of phycoremediation offers an opportunity for
reducing the environmental impact of various pollutants. This forms an effective and
economic biological treatment of polluted waters. Many micro and macro algae are
being used in various bioremediation techniques especially in polluted waters. The
intimate association which the algae have with the aquatic habitat makes them an
interesting tool for such studies. The three micro algae employed were found efficient
in phycoremediation. Chlorella vulgaris, Synechocystis salina and Gloeocapsa
gelatinosa grow well in polluted habitats and can be used for phycoremediation pur-
poses. The removal efficiency all these algae were very high. It shows that Gloeocapsa
gelatinosa is more efficient than Chlorella vulgaris and Synechocystis salina for
phycoremediation purposes.
Though further studies are needed for scaling up this study to field level the
present investigation strongly suggest that these micro algae can be utilized for
phycoremediation. Other algae may also be scanned for bioremediation potentials to
be used along with Chlorella vulgaris, Synechocystis salina and Gloeocapsa
gelatinosa. This phycoremediation technique can be used to clean up waste waters
and industrial effluents.
The authors acknowledge the University Grants Commission for the financial
assistance provided for the completion of this investigation.
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... For this study we reduced the model to its steady state conditions at 25 ºC. Under these assumptions, the change rate of the cell number density (X(t)) is expressed by (1). ...
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... Many studies used microalgae for biological treatment and a group of algae showed efficiency in reducing nutrients represented by the forms of nitrogen and total and effective phosphorus of wastewater treatment plant (Al-Rubaie, 2003 and Dominic et al. 2009) used green algae such as Chlorella vulgaris and two blue-green algae Gloeocapsa gelatinosa and Synechocystic salina in the treatment of industrially polluted water and he explained that all of them were efficient in reducing organic load (Vijayakumar and Manoharan, 2012). ...
Chromium is considered to be an environmental pollutant and a threatening agent to human health. Due to the industrial applications of this particular metal, usage presently is unavoidable and hence requires remediation technologies. There are several technologies employed for remediation of chromium, among them bioremediation finds a first and foremost place as it is cheap and environmentally friendly. Availability and toxicity of chromium depend on its speciation where Cr (VI) is highly toxic and Cr (III) is less toxic. Plants lack specific transport mechanisms for chromium and it invades the plants with other essential ions such as sulfates and iron. Microorganisms are employed for remediation of chromium affected soils which not only removes the pollutants from the soil but also helps to grow crops in those contaminated sites. Among the microbes, AM fungi have proven to be a good candidate to remove the contaminant through a process called rhizofiltration, where the chromium remains in the roots without being translocated to the vegetative and reproductive parts of the plants. Microorganisms have adapted several mechanisms to overcome chromium toxicity, including biosorption, solubilization, complexation, precipitation, binding, and dilution. In recent years, the popularity of using bioremediation techniques for decontaminating polluted sites is increasing and researchers are concentrating efforts on using microbial remediation to overcome chromium contamination. This chapter gives an overview of the above-discussed points and gives additional insight into microbial remediation of chromium.KeywordsMicrobial metabolismChromiumBioremediationRhizofiltration
Phycoremediation, which uses the purifying capacity of microalgae and macroalgae to eliminate or biotransform contaminants, has emerged as a technology for wastewater treatment. The objective of the present work is to evaluate the potential of Chlorella vulgaris to remove nutrients present in effluents generated in a dairy farm and to know the concentration of chlorophyll a and the percentage of crude protein in the algal biomass obtained. Chlorella vulgaris was grown in culture medium with 25% effluent from dairy production for seven days. At the beginning and end of the assay, the following variables were determined: ammonium, nitrites, nitrates, total phosphorus, biological oxygen demand (BOD), chemical oxygen demand (COD), and pH. In addition, the amount (%) of crude proteins and chlorophyll-a were quantified in the obtained algal biomass. At the end of the assay, the following parameters decreased: ammonium, BOD, and COD=97.1%, 81.7%, and 80.8% respectively. In the pellet, chlorophyll-a and the percentage of proteins reached values of 1.68 μg L-1and 3.75 % respectively. The results demonstrate the potential of C. vulgaris for the reduction of pollutants. In addition, it was shown that effluents from dairy production may be a less expensive alternative for the growth of microalga, with environmental and economic benefits.
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Removal of nitrogen and phosphorus from wastewater by two green microalgae (Chlorella vulgaris and Scenedesmus rubescens) was investigated using a novel method of algal cell immobilization, the twin-layer system. In the twin-layer system, microalgae are immobilized by self-adhesion on a wet, microporous, ultrathin substrate (the substrate layer). Subtending the substrate layer, a second layer, consisting of a macroporous fibrous tissue (the source layer), provides the growth medium. Twin-layers effectively separate microalgae from the bulk of their growth medium, yet allow diffusion of nutrients. In the twin-layer system, algae remain 100% immobilized, which compares favourably with gel entrapment methods for cell immobilization. Both microalgae removed nitrate efficiently from municipal wastewater. Using secondary, synthetic wastewater, the two algae also removed phosphate, ammonium and nitrate to less than 10% of their initial concentration within 9days. It is concluded that immobilization of C. vulgaris and S. rubescens on twin-layers is an effective means to reduce nitrogen and phosphorus levels in wastewater.
Phycoremediation applied to the removal of nutrients from animal wastewater and other high organic content wastewater is a field with a great potential and demand considering that surface and underground water bodies in several regions of the world are suffering of eutrophication. However, the development of more efficient nutrient removal algal systems requires further research in key areas. Algae growth rate controls directly and indirectly the nitrogen and phosphorus removal efficiency. Thus, maximum algae productivity is required for effective nutrient removal and must be considered as a key area of research. Likewise, low harvesting costs are also required for a cost-effective nutrient removal system. The use of filamentous microalgae with a high autoflocculation capacity and the use of immobilized cells have been investigated in this respect. Another key area of research is the use of algae strains with special attributes such as tolerance to extreme temperature, chemical composition with predominance of high added value products, a quick sedimentation behavior, or a capacity for growing mixotrophically. Finally, to combine most of the achievements from key areas and to design integrated recycling systems (IRS) should be an ultimate and rewarding goal.
Treatment of dye industry effluent using the cyanobacterium, Oscillatoria brevis, not only removed the organic and inorganic chemicals from the effluent but also reducing the intensity of colour from the effluent. The results revealed that within 30 days, more than 60 per cent of colour has been removed from the effluent. Nutrients such as nitrates and phosphates have been completely removed. An increase in DO content and reduction in BOD and COD upto 90 per cent have been reported. Though the effluent supported the growth of Oscillatoria, the growth was not well pronounced as compared to control. It is concluded that Oscillatoria can successfully be used not only to reduce pollution load but also for colour removal purpose.
In locations where total solar energy inputs average 400 langeleys or more, microscopic algae, grown in properly designed ponds, can contribute significantly and economically to wastewater treatment. While growing, microalgae produce an abundance of oxygen for microbial and biochemical oxidation of organics and other reduced compounds and for odor control. Microalgae also accelerate the inactivation of disease bacteria and parasitic ova by increasing water temperature and pH. Microalgae remove significant amounts of nitrogen and phosphorus and adsorb most polyvalent metals, including those that are toxic. After growth in properly designed paddle wheel mixed high rate ponds, microalgae settle readily, leaving a supernatant free of most pollutants. Such effluents are suitable for irrigation of ornamental plants, crops not eaten raw, aquaculture, and grounwater recharge. The settled and concentrated microalgae may be used for fertilizer, for fermentation to methane, or, assuming no toxicity, for fish, bivalve, or animal feed.
Wastewater arising from the production of sago starch has a high carbon to nitrogen ratio, which is improved with anaerobic fermentation in an upflow packed bed digester. The digested effluent with an average C: N: P ratio of 24: 0.14: 1 supported growth of Spirulina platensis (Arthrospira) with an average specific growth rate (µ) of 0.51 day −1 compared with the average µ of 0.54 day −1 in the inorganic Kosaric Medium in a high rate algal pond. Supplementation with 6 mM urea and 2.1 mM K 2 HPO 4 produced gross biomass productivity of 14.4 g m −2 day −1. A flow-rate of 24 cm s −1 increased the µ and gross biomass productivity (18 g m −2 day −1). The highest crude protein, carbohydrate and lipid contents of the biomass were 68%, 23% and 11%, respectively. Percentage reductions in chemical oxygen demand, ammoniacal-nitrogen and phosphate levels of the digested effluent reached 98.0%, 99.9% and 99.4% respectively. The HRAP offers a good treatment system for sago starch factory wastewater.
The potential environmental impact of effluent from fish farms is of increasing environmental concern. Although concentrations in total nitrogen and phosphorus are usually low, their impact on the environment cannot be ignored because of the high nutrient mass flows utilized during fish farming. In this paper we investigated the use of a non-toxic cyanobacterium, Phormidium bohneri, to remove dissolved inorganic nutrients from fish farm effluents. Wastewater was directed toward three completely mixed 70 1 photobioreactors with retention time of 8, 12 and 24 h, respectively. Average efficiencies of ammonia nitrogen removal from rainbow trout (Oncorhynchus mykiss) effluent was 82% and 85% for soluble orthophosphate, over a 1 month period. From these results, the potential use of P. bohneri as an alternative for the tertiary treatment of fish farm effluents is analyzed.
Synthetic wastewater enriched with either peptone or urea as organic-N source was used to grow Chlorella pyrenoidosa under axenic and open conditions. Commercial Bristol medium was used for comparison. The growth rate constant in the peptone-rich wastewater was comparable to that in Bristol medium (k=0.30 d−1 vs. 0.31 d−1) and much higher than its open counterpart (k=0.16 d−1). Both axenic and open peptone cultures exhibited a N-limiting condition for growth as revealed from the inorganic N/P ratios of 0.40 and 1.63 on day 5, which correlated with the rapid removal of 99% and 80% of NH4-N, respectively. Better growth in axenic culture was supported by the simple amino acids of the nutritive peptone which was depleted due to bacterial consumption in the open culture. The growth rate constant in the urea set under open condition was slightly higher than that of the axenic culture (k=0.20 d−1 vs. 0.15 d−1), while both were significantly lower than that in Bristol cultures. Growth in the urea set was P-limited as reflected from the high inorganic N/P ratios in open and axenic cultures, with values of 30.6 and 44.9 on day 5, respectively. This appeared to correlate to the rapid removal of 99% and 88% of PO4-P under axenic and open conditions, respectively. Bacterial interaction through hydrolysing urea to NH4-N sustained a more neutral pH in open culture and accounted for a better growth, while the acidic pH (<4) in the axenic set definitely retarded growth. The results suggest that the degree of N and P uptake and their reduction from wastewater by Chlorella pyrenoidosa depend on the types of organic-N sources in wastewater. The presence of bacteria in the culture would also affect the microalgal growth and nutrient removal, and the bacterial effect seems to relate to the types of organic N available in the wastewater.
Dairy operations in Florida face the dual problem of water pollution and air pollution (odors) as a result of the large amounts of manure produced on the farms. Ground and surface waters are contaminated by nitrogen present in seepage and runoff. A low-cost method of treatment of dairy wastewater is to convert the dissolved nutrients to microalgae biomass in engineered ponds designed to maximize photosynthetic production through solar energy. Laboratory experiments conducted on effluent from an anaerobic lagoon of a modern dairy showed that cyanobacteria (= blue-green algae) grow well on dairy wastewater and that nitrogen removal is rapid and complete. Ammonia nitrogen concentrations were reduced from 100 mg l−1 to less than 1 mg l−1 in seven days. Maximum removal rate was 24 mg l−1 per day. Prospects for nitrogen recycling are considered.