STRATEGY TO ENHANCE THE IMOs IN WASTEWATER TREATMENT PROCESS

Laboratory scale experiments using indigenous strains of Bacillus sp., Bre’undimonas sp. and Shewanella sp. in the removal of alarming concentrations of calcium, iron, and magnesium in surface waters from mined lands and petroleum contaminated sites is well documented (Gupta et al., 2000; Philip and Venkobachr, 2001; Srinath et al., 2003; Kim et al., 2007; Fosso-Kankeu et al., 2009; Karamalidis et al., 2010). Experimental batch reactor studies by Thakur (2004) under controlled conditions showed that IMO were able to decolorize kraft pulp bleached effluent. In addition, the study also highlighted on the reduction of adsorbable organic halogens and removal of color and lignin in pulp and paper mill effluent using fungi and bacteria. The study involved identification of eight potential fungal and three bacterial isolates from various sources such as decomposed wood, sediment core and pulp and paper mill effluent. Fungi such as Paecilomyces sp. (F3) was found to be more effective as decolorizing strain followed by F5 (Phoma sp.) and F7 {Paecilomyces varioti). Additionally, Paecilomyces sp. (F3) was able to reduce 80% color and lignin. Whereas bacteria such as Pseudomonas aeruginosa, Acinetobacter calco- aceticus, and Klebsiella pneumoniae removed color up to 45%, 39%, and 25%, respectively. Furthermore, the study indicated that percentage reduction of color and lignin enhanced when both fungal and bacterial strains were simultaneously applied.

Haq et al. (2016) isolated the novel bacterial strain Serratia liquefaciens (LD-5) from pulp and paper mill effluent, capable of decolorizing Azure В dye. Wherein they found that under optimal conditions of temperature (30°C), pH (7.6) and constant shaking (120 rpm) for 144 h, Serratia liquefaciens (LD-5) was able to decolorize up to 72%, and further degrade lignin and phenol up to 58% and 95%, respectively. In addition, residual toxicity of the treated effluent was evaluated by alkaline single cell gel electrophoresis assay wherein toxicity reduction to treated effluent was 49.4%. Thus, their study demonstrated the potentiality of Serratia liquefaciens as novel bacterium for bioremediation of pulp and paper mill effluent.

Abdelouas et al. (1998) reported the reduction and immobilization of Uranium (VI) species in uranium-contaminated groundwater by indigenous bacteria Pseudomonas aeruginosa, P. stutzeri and Shewanella putrefaciens. Indigenous iron-oxidizing bacteria, viz. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans are reported to be potential bioleaching agents for heavy metals across sewage sludge (Tyagi et al., 2013). A study by Xiang et al. (2000) suggested that indigenous iron- oxidizing bacteria significantly removed heavy metals such as Cr, Cu, Zn, and Ni from the anaerobically digested sewage sludge. In another study, Pathak et al. (2009) reported the potential of indigenous iron-oxidizing microorganisms enriched with ammonium ferrous sulfate, and ferrous sulfate as an energy source could yield reduced concentrations of heavy metals across sludge. A recent study by Garcha et al. (2016) reported the isolation and characterization of ten potential indigenous bacterial strains belonging to genera Bacillus sp., Escherichia sp., Lysinibacillus sp. and Brevibacillus sp. from daily wastewater and sludge. Their study indicated that bioaugmentation of these potential isolates reduced the BOD, TSS, and oil and grease content up to 89.8, 88.6, and 96.9%, respectively.

Studies have shown that the application of mixed cultures to the waste treatment is generally more pronounced and effective than that of using a single microbial culture. Bala et al. (2015) reported the reduction of organic load palm oil mill effluent using indigenous bacteria such as Micrococcus luteus, Stenotrophomonas maltophilia, Bacillus cereus, Providencia vermicola, Klebsiella pneumoniae, and Bacillus subtilis. These bacteria showed an increased reduction of BOD and COD in the wastewater. Further, their study indicated that mixed cultures of selected bacteria Bacillus cereus and Bacillus subtilis were more effective treatment for palm oil mill effluent. Several field application studies have been conducted previously for assessment of EM and IM technologies as fertilizer from food processing effluent (Wood et al., 2002). Mbouobda et al. (2013) carried an experiment that application of EMO and IMO manure on Colocasia esculenta crop. Their study showed that upon EMO and IMO manure treatment in a randomized complete block design (RCBD) design for five months, EMO manure significantly influenced the growth of Taro (Colocassia esculenta) followed by IMO manure. Further, the phenolic content, peroxidase, and polyphenol oxidase enzyme activities were higher with respect to EM treated plants. However, their study indicated that EM and IMO manure was ineffective controlling the leaf blight disease. In another study by Mbouobda et al. (2014) repotted that Irish potato (Solamtm tuberosum) treated with EM and IMO Bokashi resulted in increased growth and productivity. Additionally, phenol content, PME, PPO, and POX activities were enhanced among the treated plants when compared to control plants.

EFFECT OF EMO ON THE QUALITY OF TREATED WASTEWATER

The use of EMOs in the biochemical decomposition of wastewaters mostly depends on bacteria, produce stable end products, and waste is converted into carbon dioxide, water with other nontoxic end products. More and more microorganisms are used in these days for the successful treatment of wastewater that originates from industries such as petroleum, dyes, leather, or sewage water from the municipal sources (Zhao et al., 2006). The effect of EMOs in the treatment of wastewater showed a considerable increase in BOD and decreased pH levels, and also the settlement of sludge in the treatment tank was seen to have improved. However, when compared with the treated tanks, significant solids remain as it is. The level of suspended solids in the effluent was not reduced considerably in some of the experiments conducted for the treatment of the wastewater. After EMOs application, some other parameters also showed similar results, except total suspended solids. Highly variable conditions are observed in the septic tanks during the monitoring period. Following the use of EMOs for a considerable period, the result shows the decreased alkalinity and electric conductance (EC) of the treated wastewater. Results have also revealed that the sludge volumes may considerably get reduced due to the EMO application. In the case of solids, the breakdown of the organic matter leads to an initial increase in entrained solids of the septic tank. When EMO added, there is an increase in the reliability of the microbial ecosystems, which are ‘notoriously fragile' and pathogenic microorganisms get excluded due to competition, which in turn favors microbes that are beneficial and already present in the process. Due to the chemically stining of the sludge, the septic tanks show variance in the results, which leads to the changes in the EC, total alkalinity, and pH of the water undergoing treatment. Certain parameters such as pH can be influenced, if the microbial populations are disturbed at any trophic level, and the impact can also be seen on the other intermediates such as the complete microbial community and overall efficiency of the treatment tank (Linich, 2001).

A study was conducted by Melamane et al. (2007) and Manyuchi and Ketiwa (2013) on petroleum wastewater to remove the organic pollutants by treating with various biological methods such as activated sludge reactors or biofilm-based reactor. The wastewater from petroleum industries and refineries mainly contains organic matter, oil, and other compounds. The wastewater arising from the petroleum refinery contains compounds that are hazardous with adverse effects on the ecosystem. The treatment occurs in two stages, firstly, pre-treatment stage where oil, suspended materials, and grease are reduced. Secondly, degrade, and decrease the pollutants by an advanced method to acceptable values. Based on the availability of dissolved oxygen (DO), biological treatment methods are generally divided into aerobic and anaerobic methods (Zhao et al., 2006). The products of chemical and biochemical reactions in the anaerobic system produce displeasing odors and colors in water. Thus, to reduce this, oxygen availability is vital (Attiogbe et al., 2007). The organic compounds and recalcitrant components in an aerobic biological process are converted into CO,, water, and solid biological products. Anaerobic biological technology is highly efficient and is been widely applied in wastewater treatment (Lettinga et al., 2001).

In a study conducted by Zhao et al. (2006) on petroleum refinery wastewater using a reactor immobilized with EMOs showed the degradation efficiencies of 78% total organic carbon (TOC) removal and 94% oil removal. Similarly, Satyawali and Balakrishnan (2008) showed an unproved chemical oxygen demand (COD) removal by the aerobic biological process. Recent advances have lead to the building of a reactor called as up-flow anaerobic sludge bed reactor for the treatment of petroleum wastewater- design which is simple with easy maintenance and construction (Rastegar et al., 2011). For efficient removal of COD up to 81.07%, an anaerobic packed-bed biofilm reactor was used in combination with an up-flow anaerobic sludge blanket reactor (UASB) in the treatment of petroleum refinery effluents (Nasirpour et al., 2015). Several types of bioreactors with EMOs are used for the successful treatment of petroleum refinery wastewater such as the anaerobic treatment process (a UASB reactor) by Gasirn et al. (2013) with the efficiency of removing COD levels as high as of 82% and conversion of half of the organic compounds into biogas. Another experiment conducted by Zou (2015) showed that the oil in the heavy oil wastewater, COD, and ammonia nitrogen (NH₃-N) were removed by 86.5,

90.8, and 90.2%, respectively when biological aerated filter (BAF) system was used in combination with UASB. Temperature plays a vital role in the biotransformation of total naphthenic acids (NAs) through the activated sludge system (Wang et al., 2014, 2015, 2016). The study revealed that the percentage of removal efficiency in summer for total NAs was 73% higher than winter 53% because in the activated sludge system, the microbial biotransfonnation activities are high in summer.

A. terreus and R. sexuaJis are two fungi whose enzymatic productivity was checked by growing in non-composted sawdust and municipal sludge enzymatic contents and were tested afterl4 days of incubation. It was seen that the concentration of a-amylase and cellulase were low in the municipal sludge, and also the non-composted sawdust. Similarly, protease and a-amylase enzymes were found to be in lower concentrations in non- composted sawdust. The enzymes, such as cellulase and a-amylase, are derived from the composted sawdust due to the luxuriant fungal growth serving as a store of enzymes. The sawdust attaches to the surface working together with the microbial film, and it acts as a good supporting matrix. Apart from this, it has several other benefits, such as a good nutrient source and slow biodegradable material that can be effectively used in the treatment of wastewater. A drastic effect on the quality of wastewater was seen with the application of non-composted sawdust with respect to COD and BOD. The use of pure fungal growth is seen as highly efficient in the process of wastewater treatment. Significant results were obtained during the biological treatment processes for the total dissolved solids (TDS) ratio by pure fungal pellets or fungal-sawdust compost (bio-mixture) after 8 h of incubation (retention time) could be reduced by 67.5-74.6%. Starch decomposition up to 90% was achieved in the treatment process of starch- wastewater by fungal pellets of Aspergillus niger when applied for 16 days (Fujita et al., 1993).

In another treatment method to biodegrade, the dairy effluent waste- water, yeast isolate, and two bacterial isolates were isolated from the daily sludge with a model consisting of layers of sawdust and activated charcoal was used as a filtering media. A mixed culture of yeast and a microbial isolate was prepared by taking 1:1 ratio. Each isolate and the mixed culture were used as an inoculum to treat the diaiy wastewater. Among all the isolates, a mixed culture of dairy sludge proved to be most efficient in the treatment of wastewater after 48h aeration period. The reduction efficiency of the mixed culture was highest by 47.52% in BOD when compared with other isolates. Studies suggested that the use of mixed culture after the

48h aeration period is more effective in the treatment of wastewaters. It can reduce some of the physicochemical parameters of wastewater. The reduction in the total solid content, BOD, TDS, COD, EC, chlorides, and sulfates were caused by the bacterial isolate being the second most effective in the treatment. However, for the reduction in the turbidity and oil and gas content, yeast isolate was found to be a more helpfiil and effective single culture whereas, the final conclusion is that the mixed culture would prove to be more beneficial and effective than a single culture.