**17. Conclusions**

One advantage of biosorption is the removal of residual or minute concentrations of contaminants. Conventional water treatments may not completely remove contaminants. Hence, biosorption may be integrated downstream of other conventional water treatments. This is especially relevant in the case of pollutants like heavy metals whose effects are felt even at ppb levels.

The efficiency for the removal of specific metals is hindered by the presence of other contaminants. This may be important during the recovery of specific metals of economic value. In this regard, biosorption may be applied to wastes and effluents before it enters the sewage or natural discharge streams like rivers, seas and so on.

Later, different combinations of treatments (LOM/BIOS/ALD, BIOS/ALD and LOM/ALD) were executed to treat AMD. The volume of the initial reactor was 30 L except in the case of LOM/ALD (20 L). The downstream reactors were of 4 L. With LOM/BIOS/ALD, As, Cd and Cu were removed beyond detection. Fe and Zn were also reduced by 93 and 50%, respectively. The pH was increased to 6.3. With the BIOS/ALD system, pH increased to 6.3 and As, Cd, and Cu were removed beyond detection. Metal Al was reduced to 0.7 ppm while Fe and Zn were removed at 99 and 38% efficiency. BOD and COD were negligible. There was no influence of low temperature. The LOM/ALD was referred as the best treatment, achieving the removal of all metals including Zn (99%) and Mn (68%), not attained with other combinations, along

AquaSorb is a granular, powdered, and extruded activated carbon used primarily for the treatment of water, waste liquid streams and the recovery and recirculation of process liquors. The source of carbon which is activated for water treatment is from coconut shell, coal, and wood raw material by chemical or steam activation. Specially designed AquaSorb for the use in liquid phase adsorption systems in the range of granular, ground, and extruded (pelletized) form can be supplied by Jacobi Carbons. It can be applied as home water filters for the dechlorination of water, in order to reduce chloramines and produce water with good taste, more pure and palatable than the normal municipal water (https://www.wateronline.com/

The highest grade of Sphagnum Peat Moss is used for the development of P.O.L. Sorb which acts as a superb adsorbent for solutions due to the inherent capillary action of the activated peat which provides powerful wicking action that encapsulates oils, solvents, heavy metals, pesticides, herbicides, and so on which are in contact. It is manufactured by The ARK Enterprises, Inc. The raw material of POL Sorb is leafy, stem free, and least an abundant part of the peat in its natural or partial biodegraded state (http://www.arkent.com/POL%20

MSR is a biosorbent produced by immobilizing the inactivated cells of *Rhizopus arrhizus* with the desirable particle size of 0.5–1.2 mm. The characteristic features of the biosorbent are that it is resistant to chemicals, compression and abrasion, high porosity, and is with good wetting ability. These proprietary immobilized particles (MSRs) were used for the recovery of

One advantage of biosorption is the removal of residual or minute concentrations of contaminants. Conventional water treatments may not completely remove contaminants. Hence, biosorption may be integrated downstream of other conventional water treatments. This is especially relevant in the case of pollutants like heavy metals whose effects are felt even at

The efficiency for the removal of specific metals is hindered by the presence of other contaminants. This may be important during the recovery of specific metals of economic value. In

with negligible BOD and COD [225].

98 Biosorption

doc/aquasorb-activated-carbon-0001).

uranium from lore leaching operations [226].

Sorb%20Flyer.pdf).

**17. Conclusions**

ppb levels.

However, with the aim of treating effluent/remediating water resources of all/most contaminants, it may be an advantage to have all pollutants (metal or contaminants) removed simultaneously using a non-specific/non-selective biosorbent and reducing the number of operations/steps. Multiple biosorbents of different specificities/selectivities can also be used.

The strains or biomass used as the biosorbent should be of safe origin especially for water treated for human or animal consumption. Hence, pathogens and toxin-producing organisms need to be avoided. In this regard biomass from food-grade microorganisms like lactic acid bacteria and (wine/beer yeast) and agro-waste is of significance.

Regeneration and immobilization of biomass in order to reduce the cost of biomass involve the use of hazardous solvents which can lead to pollution. Hence, the use of harmless chemicals may be explored.

The existing waste can be classified as solid (degradable and non-degradable) and liquid in nature. A lot of solid non-biodegradable wastes (plastic) can be recycled to form chemically and mechanically robust and inert matrices to hold the biosorbent. Degradable wastes or biomass (agricultural/domestic/industrial) can be employed as biosorbents. A compatible biosorbent-matrix combination can then be employed to treat liquid discharge/effluents. This can make the waste treatment economical and sustainable while addressing the problems of solid and liquid effluents simultaneously.

Nature provides a diversity of biomass varying in binding specificity, efficiency, and ruggedness. This diversity can be tailored to site-specific waste treatment needs by applying the advanced techniques of recombinant DNA technology, synthetic biology and so on. Strains can be modified to express single/multiple metal-binding proteins on the cell surface. Chimeric proteins with multiple metal-binding domains having suitable binding and regeneration conditions can be engineered and expressed. Binding and regeneration conditions for the biosorbents can also be manipulated. Strains tolerant to harsh waste environments, and/or able to accumulate the toxic metals can be developed. However, laws regulating the dispersal or release/containment of genetically modified organisms will need to be considered. Techniques like genome shuffling are considered natural and can be employed for the modification of microorganisms. Confusion exists on the Crispr–Cas9 technology if it can be considered a genetic modification. Also, biosorption processes involving dead biomass may be a convincing argument against such regulations.

Nanotechnology is a cutting-edge technology involving the development of novel materials through the manipulation at nanoscale. The use of biomass has been explored to produce nanometal particles of silver, Cu, gold and so on. This novel use of biosorption linking the wastewater treatment to synthesis/the recovery of metals/nanometals from wastewater makes economic sense for capital investment.

The development of novel efficient biosorbents (nanocellulose, nanocomposites like pectin/ TiO2 , nano Fe<sup>3</sup> O4 /*Sphaerotilus natans*, ostrich bone waste-zero valent iron, polyaniline-modified nanocellulose) has also been obtained by varied treatments including solvents, heat, and so on. This may be the answer to optimizing and economizing biosortion-based waste treatment by improving stable efficient biosorbents.

The challenges encountering biosorption are similar to those faced by membrane filtration technology before achieving relevance and popularity as today. This includes the cost and stability of the biosorbent (membrane), the decrease in binding sites (fouling), and poor understanding and general reluctance to adopt new technologies etc. Hence, given its eco-friendly

Application of Biosorption for Removal of Heavy Metals from Wastewater

http://dx.doi.org/10.5772/intechopen.77315

101

nature and other merits, it will find its place as a routine water treatment process.

Sri Lakshmi Ramya Krishna Kanamarlapudi, Vinay Kumar Chintalpudi and

Department of Biotechnology, Koneru Laxmiah Education Foundation (A Deemed to be

[1] Baroni L, Cenci L, Tettamanti M, Berati M. Evaluating the environmental impact of various dietary patterns combined with different food production systems. European

[2] UIET SH. Environmentally sound technologies for wastewater and stormwater management: An international source book. International Water Association: Osaka. 2002;

[3] Vieira RH, Volesky B. Biosorption: A solution to pollution? International Microbiology.

[4] Das N, Vimala R, Karthika P. Biosorption of heavy metals—An overview. Indian Journal

[5] Monachese M, Burton JP, Reid G. Bioremediation and tolerance of humans to heavy metals through microbial processes: A potential role for probiotics? Applied and

[6] Verma R, Dwivedi P. Heavy metal water pollution—A case study. Recent Research in

[7] Tchounwou PB, Yedjou CG, Patlolla AK, Sutton DJ. Heavy metal toxicity and the environment. In: Molecular, Clinical and Environmental Toxicology. Vol. 101. Basel:

[8] Alluri HK, Ronda SR, Settalluri VS, Bondili JS, Suryanarayana V, Venkateshwar P. Biosorption: An eco-friendly alternative for heavy metal removal. African Journal of

\*Address all correspondence to: sudhamani1@rediffmail.com

University), Vaddeswaram, Guntur, Andhra Pradesh, India

Journal of Clinical Nutrition. 2007;**61**:279

of Biotechnology. 2008;**7**:159-169

Science and Technology. 2013;**5**:98-99

Springer; 2012. p. 133-164

Biotechnology. 2007;**6**:2924-2931

Environmental Microbiology. 2012;**78**:6397-6404

**Author details**

**References**

**15**:1-617

2000;**3**:17-24

Sudhamani Muddada\*

Biosorbents carrying metals can be included into feeds or fertilizers as metals bound to organic ligands have greater bioavailability. Also, they can enhance the shelf life of the feed involved.

However, biomass may also bind hazardous chemicals (like dyes) when used with industrial effluents. The use of such biomass into feeds is not recommended.

Biosorption is beneficial over conventional techniques. The potential has been demonstrated at laboratory and pilot scales even with actual effluent/discharges. But there is a dearth of examples in the real scenario at organized levels like municipalities/cities/pollution treatment centers/industries. Few commercial ventures have been made. This might be because of the diversity of pollutants and their chemical and biological waste background. A set of promising biosorbents/processes may need to be optimized or standardized for specific effluent types. The cost and feasibility in terms of large-scale applications may be evaluated.

Routine adoption at municipal and industrial levels requires success stories at field studies. Better metal removal efficiencies at lower costs and labor when compared to other conventional treatments can convince the industry/state to adopt biosorption. However, there is a lack of field experiments. Executing field studies needs great coordination, capital, manpower, and infrastructure.

State intervention is needed to assist the scientific community to not only fund and coordinate such large studies in terms of manpower/infrastructure but to also access the industry(s) concerned. The general indifference of the industry toward waste treatment may be an issue.

The state can act as bridge for informing and facilitating the availability of biomass from different sources to different polluting units. Such efforts will create a mutually sustainable waste treatment scenario. For example, the disposal of agro-waste from the rural setup to polluting units in order to treat effluents is a win-win for both parties.

An environment encouraging start-ups based on biosorption technology needs to be created.

Stringent norms and scrutiny against effluent discharge can convince the industry to view waste treatment as a necessary investment rather than an avoidable overhead cost. Under this scenario start-ups like Biosorbex, investing in eco-friendly waste treatment technologies, can flourish.

Efforts may be devoted to also apply biosorption at domestic (household) or community levels rather than awaiting the installation of large centralized water treatment setups.

Techniques like response surface methodology, artificial neural networking, boosted regression tree, and genetic algorithm may be used for process optimization. Modeling should be done in solutions with multiple metals and organic matter simulating the real wastewater conditions. Pilot and field studies should be conducted comparing biosorption with the conventional techniques. The use of computer-based simulations or modeling can reduce the number of field trials.

The challenges encountering biosorption are similar to those faced by membrane filtration technology before achieving relevance and popularity as today. This includes the cost and stability of the biosorbent (membrane), the decrease in binding sites (fouling), and poor understanding and general reluctance to adopt new technologies etc. Hence, given its eco-friendly nature and other merits, it will find its place as a routine water treatment process.
