Subhabrata Dev

Improvement of the degradation of sulfate rich wastewater using sweetmeat waste (SMW) as nutrient supplement.

External dosing of sweetmeat waste (SMW) dosing into exhausted upflow packed bed bioreactor (PBR) resulted in prompt reactivation of SO4(2-) removal. Different SMW concentrations in terms of chemical oxygen demand (COD)/SO4(2-) ratios (1, 2, 4 and 8) were introduced into four identical PBR where process stability was found within 3 weeks of operation. SO4(2-) removal was proportional to COD/SO4(2-) ratios up to 4 at which maximum sulfate removal (99%) was achieved at a rate of 607 mg/d. The value of COD consumption:SO4(2-)removal was much higher at ratio 4 than 8 whereas, ratio 2 was preferred over all. Net effluent acetate concentration profile and total microbial population attached to the reactor matrices were corresponding to COD/SO4(2-) ratio as 4>8>2>>1. Sulfate reducing bacteria (SRB) population was found to be inversely proportional to COD/SO4(2-) ratio in which acetate oxidizing SRB and fermentative bacteria were the dominant.

Suitability of different growth substrates as source of nitrogen for sulfate reducing bacteria

Sulfate reducing bacteria (SRB) mediated treatment of acid mine drainage is considered as a globally accepted technology. However, inadequate information on the role of nitrogen source in the augmentation of SRB significantly affects the overall treatment process. Sustenance of SRB depends on suitable nitrogen source which is considered as an important nutrient. This review focuses on the different nitrogen rich growth substrates for their effectiveness to support SRB growth and sulfate reduction in passive bioreactors. Compounds like NH4Cl, NH4HCO3, NO3−, aniline, tri-nitrotoluene, cornsteep liquor, peptone, urea, and chitin are reported to have served as nitrogen source for SRB. In association with fermentative bacteria, SRB can metabolize these complex compounds to NH4+, amines, and amino acids. After incorporation into cells, these compounds take part in the biosynthesis of nucleic acids, amino acids and enzyme co-factor. This work describes the status of current and the probable directions of the future research.

Dosing System Performance Studies

The sulfate and metal-rich wastewater collected from a coal and a metal mine was treated for 211 days using two identical anaerobic bioreactors packed with spent mushroom compost. The decrease in treatment efficiency after 85 and 101 days of operation in the bioreactor treating the coal and metal mines, respectively, was mainly due to organic carbon exhaustion. Subsequent supplementation of the bioreactor with sweetmeat waste, NH 4 HCO 3 , and NaHCO 3 at optimized dosing conditions resulted in rapid reactivation and improvement of the wastewater treatment. Until the end of the operation, the sulfate was removed up to 97–99% from both the mines wastewater. Similarly, the Fe, Mg, and Zn were removed at 99%, and Cu at 80% from the coal mine wastewater. The Cu, Zn, and Mg were removed at more than 95% from the metal mine wastewater. The concentration of targeted pollutants in the treated effluent was far below the effluent discharge limit of Indian standards.

Reactivating Bacterial Community and Biochemical Events

Static and continuous experiments were carried out in a down-flow chemo-bioreactor and modeled on successive alkalinity producing systems, for treatment of acid mine drainage. Spent mushroom compost (SMC) was used as the immobilizing substrate and nutrient source for sulfate reducing bacteria. Operational success was assessed using effluent to influent ratios during continuous flow; the average was: 0.0175, 0.12, and 0.071 for Fe, Cu, and Mn, respectively, and 0.11 for sulfate. In contrast, Mg was released by the SMC, increasing its concentration in the effluent. The pH of the effluent was >7 for most of the experiment. After a certain period of time, the SMC was exhausted of dissolved organic carbon when reactivation of the bioreactor would require supplementary dosing substrates. This chapter begins the discussion to deal with the challenges of reactor and process reactivation that would form a major part of engineered bioremediation plants.

Design of Wastewater Bioremediation Plant and Systems

So far we have established that bioremediation of industrial wastewater, the likes of which we get from the mining, metallurgical, civil, and construction industries, faces the challenges of flow, unsteady effluent quality, stalling of biochemical reactions, slippages, and pH control, etc. Much of the problem is generated from the exhaustion of essential nutrients like C, N, and others. So we have proposed a dosing mechanism, suitable nutrient design and delivery; the result is highly encouraging. The design of a biological wastewater treatment plant—the focal point of this chapter—requires the consideration of certain parameters such as area availability, site characterization, characteristic flow rate, retention time, pH, organic loading rate, and treated water discharge quality. Selection from different combinations of processes and unit design is based on criteria like reliability, cost-effectiveness, performance, adaptability to the influent quality variation, ease of construction, labor skills, sludge, energy requirement, etc. In addition, economic feasibility should also be considered in the complete design.

Nutrients for the Selective Growth of Specific Bacteria

Nutrients play an important role in the growth and activity of any bacteria, no less in the case of sulfate reducing bacteria (SRB). Nutrients provide for growth and resilience. Different simple and complex organic substrates have been reported to serve as electron donors, carbon, and nitrogen sources for SRB. The growth of SRB not only depends on the availability of these nutrients, but also on the C/N ratio. The optimum C/N ratio for SRB depends on the source and characteristics of the substrates and other substances present that control release. In association with fermenting bacteria, the SRB metabolize the substrates using a complex and nonuniform pathway. The metabolism of the carbon sources is via complete and incomplete oxidation processes, whereas some SRB strains utilize the tricarboxylic acid cycle. This chapter describes state-of-the-art research in the area, and relevant findings for the ongoing discussion.

Effectiveness of Marine Waste Extract as a Suitable External Nutrient Source

Marine waste extract (MWE) was able to support comparably higher sulfate removal and SRB growth than Lactobacillus fermented marine waste extract and other commercially available nitrogen sources. The modified growth medium supplemented with MWE, to be known as MSRB, was found to be sufficiently nitrogen-rich, and was comparable to standard SRB growth media such as Postgate B, modified Postgate B, and Widdel and Pfennig in terms of nutritional characteristics. The MSRB was able to support better growth of SRB, and higher sulfate removal as compared to the standard growth media. Improvement in SRB growth and sulfate removal was achieved by optimizing the SRB growth related parameters like pH, sulfate, and MWE concentration when used with single and multiple parameter optimization methods. The findings of the study point to the current development of material and methods that are both cheap and more effective than available and entrenched commercial alternatives.

Microbial Treatment of Industrial Wastewater

Industrial activities result in the production of a large quantity of polluted wastewater. The present chapter mainly focuses on the sulfate and metal-rich wastewater generated from industries such as mining, metal processing, electroplating, chemical processing, and pulp and paper processing. The contamination of water bodies with such wastewater results in aquatic ecological disability and causes various diseases, such as kidney failure, bone deformation, skin disease, and cardiovascular abnormalities, etc. The treatment of sulfate and metal-rich wastewater includes abiotic treatment and biological treatment. In biological treatment strategy the sulfate reducing bacteria (SRB) meditated removal of sulfate and dissolved metals is extensively used. The field application of SRB based treatment processes includes constructed wetlands, permeable reactive barriers, vertical flow systems, anaerobic bioreactors, etc. This chapter reviews the treatment processes that are influenced by factors such as pH, hydraulic retention time, temperature, pH, nutrient availability, and concentrations of sulfide, sulfate, and metals.

Preparation of a Waste as Nutrient Dose and Its Characterization

In continuation of the previous chapters, in this chapter we are discussing the preparation of nitrogen-rich growth substrates from organic marine waste discarded in the coastal areas after regular fishing activities. The substrates prepared from organic wastes by two methods—alkaline hydrolysis and Lactobacillus mediated fermentation—were termed as marine waste extract (MWE) and Lactobacillus fermented marine waste extract (MWEL), respectively. Both MWE and MWEL were rich in nitrogen and contained essential nutrients such as C, K, P, and Na in sufficient concentration, and trace elements (Fe, Mg, Mn, Zn, Co, Cu, and Ni) needed for bacterial growth. The cost estimation has shown that both MWE and MWEL were much more cost-effective than commercial nitrogen sources. Considering the large quantity required for sustained treatment on an industrial scale, the substances made from abundantly disposed materials by simple methods promises to be viable for economic use in industrial scale microbial wastewater treatment.

Improvement by Dosing in Schemes of Continuous Treatment: Findings of a Column Study

Dosing of marine waste extract (MWE) into an anaerobic packed bed bioreactor (PBR) was performed to improve the treatment of sulfate and metal-rich wastewater collected from some mining sites. The variation of sulfate and MWE concentration showed uncompetitive substrate inhibition on SRB growth. The kinetic data showed that MWE dosing improved microbial growth by 27%. The community analysis using DGGE showed the dominance of SRB (87–89%) over other microbes. The multiple process parameters such as pH, HRT, concentration of MWE, TOC, and sulfate were optimized using the Taguchi design, and the influence of them towards biological sulfate reduction was in the order of pH>MWE>sulfate>HRT>TOC. Under optimized conditions, almost all the sulfate and dissolved metals were removed from the wastewater. The study indicates the optimum dosing of organic nitrogen to promote SRB growth creates a future scope to develop a large-scale efficient treatment process.Dosing of marine waste extract (MWE) into an anaerobic packed bed bioreactor (PBR) was performed to improve the treatment of sulfate and metal-rich wastewater collected from some mining sites. The variation of sulfate and MWE concentration showed uncompetitive substrate inhibition on SRB growth. The kinetic data showed that MWE dosing improved microbial growth by 27%. The community analysis using DGGE showed the dominance of SRB (87–89%) over other microbes. The multiple process parameters such as pH, HRT, concentration of MWE, TOC, and sulfate were optimized using the Taguchi design, and the influence of them towards biological sulfate reduction was in the order of pH>MWE>sulfate>HRT>TOC. Under optimized conditions, almost all the sulfate and dissolved metals were removed from the wastewater. The study indicates the optimum dosing of organic nitrogen to promote SRB growth creates a future scope to develop a large-scale efficient treatment process.