Recent Trends and Innovations in Sustainable Treatment Technologies for Heavy Metals, Dyes and Other Xenobiotics

By Bentham Science Publishers

This book integrates knowledge about innovative technologies developed in the past decade with information about commercial-scale processes. It is written with the objective to help readers to understand the potential of achieving sustainability and high efficiency in wastewater treatment. The book presents nine chapters. Chapter 1 details the types of wastewater, its characteristics, and the major commercial-scale strategies employed to treat wastewater. Chapter 2 details the different types of physicochemical methods utilized for the remediation of heavy metals, dyes, and xenobiotics. Chapters 3 and 4 highlight innovations in the advanced oxidation process and adsorption for remediation of such complex molecules, respectively. Chapters 5, 6, and 7 highlight the recent innovations in bioremediation of xenobiotics, heavy metals, and dyes, respectively. Finally, chapters 8 and 9 discuss the latest technologies, prevailing bottlenecks, and the path ahead towards commercial viability and environmental sustainability in both physico-chemical and biological treatment processes.

• Language: English
• Publisher: Bentham Science Publishers
• Release date: Oct 7, 2003
• ISBN: 9789815049725

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Wastewater Types, Characteristics and Treatment Strategies

Uttarini Pathak¹, Avishek Banerjee², Subham Kumar Das³, Teetas Roy³, Tamal Mandal¹, *

¹ Department of Chemical Engineering, National Institute of Technology Durgapur, Durgapur, India

² Department of Chemical Engineering, McGill University, 845 Sherbrooke St W, Montreal, Quebec H3A 0G4, Canada

³ Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Dr NW, Calgary, ABT2N 1N4, Canada

Abstract

One of the most important issues in recent times is the remediation of wastewater discharged from different industries. Several of the growing economies have been investing heavily to reduce the discharged waste content for economic and environmental sustainability. The wastewater when discharged into natural water bodies harms the flora and fauna of the surrounding environment, which in turn disrupts the ecosystem and affects the food chain. It also increases and possesses a variety of health risks to human beings. To eliminate the potential threats, a critical analysis of the past research and upcoming remediation technologies is necessary. Over the years, a lot of advancements have been made to curb the disruption of the natural ecology from effluent discharges by different industries like the leather industry wastewater, Rice mill wastewater, pharmaceutical industry wastewater and Coke Oven wastewater. The common characterization techniques that are employed in all of them are to measure the COD and BOD levels, pH, odor, TSS, organic and inorganic materials. Subsequently, the common technologies that are in use to treat these wastewaters are mainly physicochemical treatments like adsorption, electro-coagulation/flocculation, nanofiltration, Fenton’s oxidation or biological treatments like aerobic/anaerobic microbial degradation. An important requirement is to understand the situation currently prevalent in wastewater treatment to develop better and advanced methods for increased efficiency and waste removal. The aim of this chapter is to give a detailed account on the composition, characterization, and treatment strategies of the discharged effluent to enhance the knowledge of available resources and instigate ideas of future improvements.

Keywords: Industries, Treatment, Dyes, Pharmaceuticals, Heavy metals.

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* Corresponding author Tamal Mandal: Department of Chemical Engineering, National Institute of Technology Durgapur, Durgapur, India; Tel: [phone]; E-mail: [e-mail]

1. INTRODUCTION

The world’s population is continuously increasing along with rapid industrialization which highlights the environmental concerns that arise from industrial wastes [1]. Industrial waste and pollution have become major contributing factors to the degradation of the environment over the years. It was observed through various investigations that almost half of the medium and small-scale industries contribute greatly to water pollution by waste discharge in natural water bodies [2]. The environmental, economic, and societal implications of waste discharge give rise to unavoidable discord between industrialization and environmental sustainability [3, 4]. Due to the mobile nature, detrimental impacts are observed on biodiversity from effluents if discharged without proper and substantial remediation [5, 6]. Also, nowadays, the discharge is from different industries like chemical, pharmaceutical, leather, textile, etc., which influences the characteristics of the discharged wastewater making it difficult to predict the composition. Hence, the treatment of these wastewaters has attracted more investigation to preserve the environment [7].

Tannery industry earns a large amount of foreign exchange through its leather export and is also one of the most important industries in India. After tanning, the effluents released contains high amount of trivalent chromium, BOD and COD levels, NaCl, sulfides, Mg, Ca, organics, and other toxic ingredients. These effluents affect the natural ecosystem and subsequently possess a variety of health risks to human beings [8, 9]. For example, in Dhapa, Kolkata (India), wastewater from nearby tanneries is disposed of that affects the food chain of human beings [8]. The standard methods of treating tannery wastewater are by adsorption [10, 11], coagulation/flocculation [12], oxidation by Fenton’s reagent [13], nanofiltration [14, 15]. Recently, bioremediation technologies are being used by the industries to degrade the generated waste either aerobically or anaerobically [16]. One of the major elements for the toxic hazardousness of the wastewater is chromium [17]. The tanning process using chrome releases about 40% of unutilized Cr salts that are often released through the wastewater, giving rise to serious environment implications [18-20]. Exposure to common tannery waste like pentachlorophenol, chromium, and other toxic pollutants increases the risk of ulcer nasal septum perforation, dermatitis, and lung cancer [21, 22].

Rice is the main staple food in India and around the world and its production has a significant role in the world economy. Huge quantities of water are required for the soaking of parboiled rice and thus a significant amount of wastewater is generated from rice production which is approximately 1–1.2 L/kg of paddy [23]. One of the most common concerns is its disposal on land that causes soil contamination and consequently results in surface and groundwater quality degradation [24]. Algal blooms that cause odor problems due to eutrophication and many other adverse effects are the outcomes of discharging untreated effluents into natural water bodies [25, 26]. Rice mill effluent has a pungent odor that is mainly yellowish in color and consists of toxic organic materials along with other impurities. Rice mill wastewater consists of COD elements like cellulose, lignin, phenol, and other humic substances that disrupt the environmental sustainability [27]. The most common technologies that are studied for remediation are physicochemical treatments like adsorption [28] and electrocoagulation [29], microbial treatment [30] and phytoremediation [3].

Human health is becoming a subject of prime importance that is leading to the rapid growth of the pharmaceutical sectors, but at the same time, these industries produce a lot of wastewater effluents that are responsible for the degradation of the environment [31]. Various microbial and toxic elements along with virulent pharmaceutical ingredients (API) are released untreated into natural water bodies. The pollutant load in municipal waste is often increased by the improper disposal of unutilized medicine along with metabolic excretion due to drugs by humans and animals, which in turn could affect the ecology and increase health hazards. Various research works have established that the presence of pharmaceutical compounds in aquatic systems often arise from pharmaceutical manufacturing plants [31-35]. Thus it affects the food chain as well as plant and animals [36, 37]. Current techniques employed to treat this wastewater in different industries are biochemical treatment [38-40], membrane filtration treatment [41], adsorption treatment [42-45] and advanced oxidation process treatment [46-51] for the removal of waste from industrial wastewater.

Coke ovens are used extensively in the steel and coal industries. Compounds like phenol and cyanide are released with the coke oven wastewater which affects the entire ecosystem, harming the flora and fauna along with the human respiratory system [52, 53]. Thus, a permissible limit of 0.5 mg/L for phenol and 0.2 mg/L for cyanide has been set by different industries for the industrial effluent according to various environmental organizations (WHO, USEPA, and CPCB, India) [54]. Different waste treatment technologies have been used in recent times that focus more on biofilm or fluidized bed reactors [55-58], membrane-based bioreactors [59], granular activated carbon [60], and immobilized spent tea activated carbon [61, 62]. Since there exists several factors like public hazards, economic feasibility of upscaling and complexity of the wastewater, the approach towards treating this water have been changed from incineration or chemical decomposition. Bioremediation has been a popular technique for remediation of phenol and cyanide with some of the major degrading organisms being Escherichia coli [63], Pseudomonas sp [64, 65], Acinetobacter sp., Bacillus sp [66, 67], Serratia odoriferra MTCC 5700, etc. Also, immobilization technique has recently been in use to overcome the drawbacks of suspension cultures [67, 68]. The different sources of wastewater generated are depicted in Figs. (1 and 2).

Fig. (1))

Different sources of wastewater generated from (a) coke oven (b) rice mill.

2. CHARACTERIZATION

2.1. Coke Oven Wastewater

Coke Oven wastewater contains a significant amount of COD and BOD levels along with high amounts of phenol, TKN and cyanide. It also contains some trace amounts of inorganic and organic materials. A detailed characterization of coke oven wastewater has been given in Table 1.

2.2. Rice Mill Wastewater

Rice mill industries discharge a significant amount of wastewater that has varying pH. It contains high amount of COD, BOD, TDS and TSS levels along with adequate lignin, phenol, and nitrogen [69], as represented in Table 1.

Fig. (2))

Different sources of wastewater generated from pharmaceutical industries.

2.3. Pharmaceutical Wastewater

This study will focus typically on the popularly consumed drugs like analgesics (Pantrapazole/Ondansetron), antidepressants (Levosulphiride), antibiotics (Ernofloxacin), antihistamines (Cetrizine) for treatment from areas having large concentrations. Identification of 118 pharmaceutical compounds with 17 therapeutic classes of drugs has been reported in different literatures from bulk drug production especially in the global drug hub area.

2.4. Leather Industry Wastewater

The wastewater produced from leather industries in Tangra, Tiljala and Topsia of Kolkata, India was collected at regular intervals, for sampling and characterization [17]. The average values of the composition of wastewater are presented in Table 1. The tanneries in Tangra, Tiljala and Topsia of Kolkata, W.B. India discharge their wastewater to nearby channels. Usually, the wastewater is drained out to the channel from the leather industry on a regular basis, reaches fishery and agricultural farms, and severely affects the food chain. In a regular interval, sampling was carried out from this channel and characterized. The average values of parameters of wastewater were as follows; obnoxious, pH 6.4–7.6, 30 oC, COD 2,533 mg/L, BOD5 977 mg/L, TDS 21,620 mg/L, ammonia-N 118 mg/L, phosphorus 62 mg/L, sulphide 860 mg/L, chloride 6,528 mg/L, conductivity 20.04 mS/cm at 25 oC, total chromium 58 mg/L, and total iron 2.56 mg/L [40].

Table 1 Characterization of different industrial effluent.

3. TREATMENT STRATEGIES

3.1. Coke Oven Wastewater

The principal compounds in coke oven wastewater are phenol, ammonia, cyanide, thiocyanate, sulfide, etc. These compounds are present in high amounts. Conventional treatments like activated sludge process can be used for its treatment. Although the problem remains that the waste generated from the process does not follow the standards of effluent generation. Biological treatments are not very effective in treating coke oven wastewater due to its high toxicity. As a result, advanced oxidation process is the best option for pre-treatment of coke oven wastewater. These advanced oxidation processes include Fenton’s treatment, UV treatment with peroxide (H2O2), UV treatment with Ozone, photo-Fenton treatment process and Contaminant degradation using ultrasonic methods. The principle of this method is based on the generation of highly reactive free radical species. It has been observed in the literature that the Fenton’s process for pre-treatment of coke oven wastewater is one of the best techniques because it is fast and highly efficient with respect to reaction kinetics. Fenton’s treatment has increased the biodegradability of the wastewater and improved the sludge dewaterability. The hydroxyl radicals in this process react non-selectively and have the ability to remove complicated contaminant species present in coke oven effluents. Although the cost of this process is high, and it can lead to substantial amounts of sludge generation often. So, it can be more effective to use the process as a pre-treatment process applied before bioremediation is performed [70].

The treatment of phenol and cyanide was investigated by Pathak et al. [68], using a mixed bacterial consortium immobilized on activated carbon infused spherical calcium alginate pellets. Response surface modelling was employed, and a central composite design was used for optimizing the packed bed bio-column and batch studies. From the study, the most favorable percentage removal in batch conditions was found to be 89.77% for phenol and 82.33% for cyanide, with 0.3 cm particles and 10 kg/m³ adsorbent, ran for 2 hours. For the bio-column system, an optimal removal of 87.22% and 90.97% of the respective contaminants was recorded with a 3 cm diameter column, with the height of 22 cm. The flow rate of the wastewater to be treated was 10 ml/min, and the operation was carried for 1 h, rendering an effective exposure time for the pollutants in the bio column of 22.15 minutes. Effective insight into the process was provided by integrating biological treatment with A. faecalis JF339228 and K. oxytoca KF303807, with alginate beads infused with activated carbon for degradation of cyanide and phenolic contaminants in batch and column optimization studies. The study also established that isolated bacterial strains were capable of tolerating the toxicity of coke oven effluent. The results predicted that the column process was far more effective than the batch one, exhibiting extreme efficacy in the coke oven wastewater treatment process, with very high removal efficiency. The mass transfer effect influenced the biological degradation process in an immobilized bio-column substantially, hence should be taken in careful consideration in future design and developments. Removal of phenol and cyanide from industrial coke oven effluent was studied by Pathak et al. [61] using activated carbon made from spent tea, modified with acetic acid (STAC-C) bacterial strain Alcaligenes faecalis JF339228. A. faecalis JF339228 immobilized onto biochar prepared from spent tea leaves by amalgamated sorption technique. GCMS anatomization was utilized for analysis of the degraded chemicals after the process. TOXTREE software was used to analyze the chemistry and structures of the same, and the effects of the disposal of these into nature. Batch experiments were carried out by varying the pH, reaction time, dosage of the adsorbent, initial concentrations, and temperature. Static and mobile cells performed better removal with effectiveness of 94.71% and 92.25%, respectively for cyanide, and the method involving STAC-C removed phenol up to 86.29%. Analysis of the feasibility of different mechanisms engaged in the modification of the organism’s genetic makeup after release into nature was conducted , and it was concluded that the intermediaries were more suitable for disposal into the environment.

Apart from phenol and cyanide, ammonia and its compounds are major contaminants in coke oven effluents but there are relatively less resources available on the removal of such compounds from wastewater, compared to phenol and cyanide. In a study [71], ammonia removal was investigated from a synthetic wastewater sample with phenol, cyanide and ammonia, using commercially available charcoal activated carbon and an acid modified variant of the same. The removal of ammonia was acceptable, and changes in the percentage removal with different initial concentrations and doses of the adsorbent used were not very drastic, but pH of the solution had a slight effect on the ammonia removal. It was also observed that by using modified charcoal, phenol removal was enhanced but the removal of ammonia remained unchanged.

3.2. Rice Mill Wastewater

Rice mills release large amounts of effluents which contain toxic inorganic and organic components which can be detrimental to the environment if they are released into the natural water bodies without any treatment. The treatments employed need to be cost effective [69]. The results of various treatment processes for wastewater effluents from rice mills are summarized below in Table 2.

Table 2 Performance of different treatment systems for rice mill wastewater treatment.

3.3. Pharmaceutical Wastewater

Huge quantities of medical and pharmaceutical wastes are generated by medicine industries which need effective disposal since they can be a major source of concern for nature. Among the major pharma wastes, levosulpiride is one which has relatively less effective treatment processes commonly known. Hence, a more effective method of degradation of levosulpiride using Ozone, activated carbon and series of biological treatments by A. faecalis JF339228 and E. aurantiacum KX008295 was investigated by Mandal et al. [72]. A synthetic aqueous solution of 600 mg levosulpiride was treated in the process using 2 g/L activated carbon and 5.2 g/h ozone and a treatment with A. faecalis JF339228 and E. aurantiacum KX008295.1 for 72 hrs yielded removal percentages of 51.60%, 53.50%, 39.97% and 37.51%, respectively. The treatment with ozone was followed by biological treatment in this study and it was observed that this combined treatment yielded better results with activated carbon, ozone, and the bacteria in small doses in comparison to the pre-existing technologies available. For a synthetic 800 mg/L levosulpiride solution, the same process recorded a removal of approximately 61%. The treatment process was affordable, green and energy efficient.

A chemical of the medical industry, Ondansetron, was removed from pharmaceutical effluents using adsorption by Mandal et al. [73]. The adsorbent used was coffee husk activated carbon (CBH) [1], Ozone (O3) and a biological treatment by A. faecalis JF339228 and E. aurantiacum was employed. A simulated aqueous solution of 800 ppm ondansetron was treated using an integrated system of 2 g/l activated carbon, 5.2 g/h O3 and a treatment using A. faecalis JF339228 and E. aurantiacum bacteria for 72 h with 81.25%, 58.80%, 70.15%, and 65.12%, respectively. This kind of simultaneous treatment was effective in degradation of Ondansetron and the percentage removal was 90% and 71% at minimum consumption of chemical and time respectively. The higher toxicity of the solution towards the beginning of the study causes a lengthy log phase of growth of the microbes, and this causes the removal of ondansetron to be slow. With the acclimatization of the bacteria, the growth rate increases and more ondansetron is consumed as a carbon-source, hence the percentage removal of Ondansetron starts increasing. The treatment with O3 showed moderate impact on the removal of this drug. Acceptability of the wastewater and the degraded intermediates for release into the environment after this treatment is confirmed by a DNA interaction study.

3.4. Leather Industry Wastewater

For the treatment of wastewater coming out of industries dealing with leather production or processing, a number of methods have been used by researchers, including biochemical degradation treatments and AOPs. The AOPs like Fenton’s treatment make the contaminants more biodegradable [48] and the use of biodegradation using Thiobacillus ferrooxidans together with advanced oxidation process using FeSO4 and H2O2 (Fenton's reagent) was investigated by Mandal et al. [17]. The authors used biodegradation using T. ferrooxidans, Fenton’s oxidation and the two processes together, in three separate experiments and showed that among the three cases, maximum BOD, COD, sulfide, total chromium and color were removed in the shortest time when a combination of both processes was used. The wastewater treatment of an effluent sample from a leather industry in Kolkata, using only Fenton's oxidation process, in which 6 grams Iron Sulphate (FeSO4) and 266 grams of Hydrogen Peroxide (H2O2) in a liter of wastewater at 3.5 pH, temperature of 30 °C for 30 minutes at batch conditions reduced COD, BOD, sulfide, color and total chromium content up to 69%, 72%, 88%, 100% and 5% respectively. Biodegradation using only T. ferrooxidans showed a maximum decrease of 77%, 80%, 85%, 89%, and 52% respectively in the above quantities, in a treatment for 21 days at a pH of 2.5, FeSO4 16 g/L, at 30 °C. The procedure combining both methods (batch conditions) consisted of a half an hour chemical treatment by Fenton's process and then a 72-h biochemical treatment by the bacteria. This method showed up to 93, 98, 72, 62 and 100 percent decrease in the COD, BOD, sulfide, chromium and color content at 2.5 pH and 30 °C. Fig. (3) depicts the variations in removal efficiency among different wastewater resources using techniques such as adsorption, biodegradation, and advanced oxidation process.

Fig. (3))

Percentage removal obtained from adsorption, biodegradation and advanced oxidation process for wastewater generated from leather, rice mill, pharmaceutical and coke oven industries.

CONCLUSION

Treatment of wastewater has been of prime importance in recent times both for the economy and the environment. The industries that are mainly discussed in this chapter are iron and steel, rice mill, pharmaceutical, and leather industries. Several treatment strategies have been used over the years for the treatment of the wastewater. For coke oven wastewater, generally a pre-treatment method involving advanced oxidation processes is used before microbial degradation which is the major treatment strategy. Microbial studies on coke oven wastewater show that microorganisms can sustain themselves in the toxic environment and provide good results of removal. For rice mill wastewater, adsorption using chitosan, electrocoagulation and microbial fuel cells provides the highest removal rates. For pharmaceutical wastewater, adsorption processes with coffee husk have shown good removal rates however ozone treatment for removal of ondansetron has given moderate results. Also, biodegradation has proven to give good removal, but the growth of microorganisms is a time-consuming process. For leather industry, it has been found out that advanced oxidation processes like Fenton’s oxidation along with biodegradation provide higher removals in the shortest time. Although AOP techniques for treating leather effluent provide good results, however a combination of both has been found out to be a better treatment strategy. Considering these recent advancements, several techniques are being applied in the industries for remediation of the wastewater. However, there lies several gaps in the current wastewater treatment scenario. Firstly, different industries discharge different kinds of wastewater that has different kinds of compositions. Even similar industries from different areas discharge effluents of different toxic levels. So, it becomes very difficult to employ a specific remediation technology for a specific industry and then set it as a standard. Moreover, laboratory experiments are prioritized over in-situ characterization due to site accessibility issues which does not give us a clear picture whereas the authors believe that in situ site remediation of at least point source of contaminants must be employed for better understanding. To overcome these challenges, we must look forward for alternatives that are vastly unexplored and would provide a better solution for treating different kinds of wastewater technologies. One such alternative would be the use of carbon nanomaterials or graphene oxides over traditional approaches. In recent times, it has been found out that functionalized CNMs, and their composites show high adsorption and catalytic degradation of toxic pollutants. These modified materials also have reasonable regeneration ability and can be effectively reused without any significant decline in performance. Thus, to implement such technologies that would help us in solving our current problems, we must invest more in our research and development sector to further study such technologies in different industrial units before it can be used in real time.

CONSENT FOR PUBLICATION

Not applicable.

CONFLICT OF INTEREST

The authors declare no conflict of interest, financial or otherwise.

ACKNOWLEDGEMENT

The authors are indebted to the National Institute of Technology Durgapur, West Bengal, India for extending their financial and instrumental support for this work.

REFERENCES