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15 Photobiological Reactors for the Degradation of Harmful Compounds in Wastewaters

as the most prominent compound among the identified fatty acids. The results of

aerobic wet digestion (batch mode) had shown the capacity of the strain KM15 for

simultaneous lipid accumulation and waste treatment. Among different types of

wastes, removal of volatile solids (VS) up to 38.5% and oxidizable organic matter

removal (COD-based) up to 48.9% and accumulation of lipids up to 41.5% in 96 hours

had been achieved by strain KM15.The degradation efficiency of organic matter was

30.9% and 31% for apple and orange waste after 96 hours with a lipid accumulation

of 21% and 25% respectively. Mostly, Bacillus cereus strain KM15 was the most effec-

tive strain in the degradation of mango waste and correspondingly, the production of

biolipids from waste. Recent study illustrates the concept of biorefinery for sustain-

able waste management and simultaneous production of lipid-based biofuels, and

another study illustrates the potential of the B. cereus strain KM15 to produce lipids

using waste as a substrate. The waste can be used as the sole source of nutrition and

could be a key factor in reducing the total production cost of lipid-based bacteriolog-

ical biorefineries. The use of B. cereus KM15 can provide a dual advantage of waste

minimization and lipid accumulation in cells. The identification of FFAs also shows

the biodiesel potential of lipids extracted from bacterial cells for the biorefinery con-

cept. Simultaneous reduction of waste in terms of VS and COD removal as well as

lipid production using fruit peel waste (FPW) could be exploited to produce biofuels

by using bacterial strains [10].

15.2.1.9

Anaerobic Degradation of Textile Dye Bath Effluent Using Halomonas

Species

The main objective of this study is to reduce the COD and color of the effluent con-

taining reactive textile dye by microbial method. Anaerobic digestion has the ability

to break down complex refractory organic compounds, so that they may be fur-

ther degraded aerobically or completely mineralized, and this technique was applied

to synthetic reactive red dye cotton textile effluent aiming at the dye degradation.

Halophilic and halotolerant bacterial cultures, Halomonas variabilis and Halomonas

glaciei, were used for the degradation in batch-mode under static condition. The

temperature was kept constant at 30 ^∘C in a CO2 incubator. Maximum degrada-

tion was achieved within 144 hours of experimental run, and degradation studies

were conducted by determining COD and BOD. Statistical analysis showed that the

BOD and COD reduction rate was optimal in the dye concentration of 1297 mg/l

within 100 hours. Recent studies have shown that the reactive dye bath effluents

can be degraded using the bacterial cultures used in this degradation process, even

in the presence of alkali enabling the treated water for recycling. The optimal val-

ues suggest that the effluent diluted to the optimized concentration can be degraded

successfully using H. glaciei in the anaerobic batch reactor with a maximum COD

reduction rate in 100 hours. Further studies on the anaerobically digested textile

effluent should include oxidation in order to reduce COD considerably. Oxidizing

the reduction products and subsequent recycling of treated wastewater will attain

zero discharge [11]. Other potential microorganisms that are extensively used in dye

removal are listed in Table 15.1.