Research: Removal of Heavy Metals from Aqueous Solution by Biofilm-forming Bacteria Isolated from Mined-out Soil in Mogpog, Marinduque, Philippines

Philippine Science Letters Research carried out by Lucille C. Villegas (1),*, Arlene L. Llamado (1), Kristine V. Catsao (FEED-UPLB Scholar 2017) (2), and Asuncion K. Raymundo (1).

  1. Microbiology Division, Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños, Laguna 4031, Philippines
  2. Euromed Laboratories Philippines, Inc., Dasmarinas, Cavite, Philippines

*   Corresponding author Email Address: lcvillegas1@up.edu.ph

  • Date received: February 26, 2018
  • Date revised: May 20, 2018
  • Date accepted: May 28, 2018

5 August 2018.  The thesis of former FEED scholar Kristin Catsao, now the Assistant QC Manager for Microbiology of Euro-Med Laboratories Inc., produced some data which the authors were able to build on to complete the study and have it published.

INTRODUCTION

Heavy metal pollution is one of the most pressing environmental concerns associated with industrialization. Heavy metals (HM), such as mercury, lead, cadmium, arsenic, chromium, zinc, copper, and manganese are incorporated into soils and waters through industrial, agricultural and domestic effluents (Jjemba 2004). When concentrations exceed normal levels, they become potentially hazardous. As they are not metabolically-degradable, concentrations increase as they progress through the food chain. Excessive amounts in humans can cause toxicity, cellular function disorders, long-term debilitating disabilities, and eventually death (Naja et al. 2010).

In the Philippines, HM-contaminated areas include abandoned mined-out sites and river systems adjacent to industrial sites such as an abandoned copper mined-out site in Mogpog Marinduque, reported to be contaminated with high levels of copper (Raymundo 2006; Llamado et al. 2013). The Meycauayan, Bulacan river system, likewise, has been reported as heavily-polluted with HM with the jewelry making , gold smelting, battery recycling, pyrotechnic, and tanneries effluents (Mendoza 2012). In tilapia fishponds, mercury and cadmium were reportedly present in the surface water and that traces of these two HM have been detected in the fish as well. The shells used for feeding prawns and ducks were found to have chromium (pureearth.org/project/marilao-industrial-waste- contamination). These findings evoke scary health scenarios which should prompt moves for proper treatment to prevent further HM contamination and spread.

The removal of heavy metals from industrial wastewater is generally done through physico-chemical methods, consisting of chemical precipitation, chemical oxidation or reduction, electrochemical treatment, evaporative recovery, filtration, ion exchange and membrane technologies (Hussein et al. 2004). However, for solutions containing 1 – 100 mg·L-1 dissolved heavy metal ions, these processes maybe ineffective or expensive (V olesky 2001). Biological methods, such as microbial remediation, may provide cheaper and yet effective alternatives.

Microorganisms have high affinity for metals. The microbial cells’ surfaces are negatively- charged due to the presence of various anionic structures and consequently are capable of binding metal cations. This specific microbial property is capitalized in biosorption which is the most prominent emerging alternative technology for removing HM as it allows the accumulation of the pollutants in both living or dead microbial cells via metabolically-independent pathways (Atlas and Philip 2005). The advantages of biosorption over physico-chemical methods include low capital outlay, metal selectivity, high efficiency, minimal chemical and biological sludge, no additional nutrient requirement, regeneration of biosorbent, and the possibility of metal recovery (Volesky 2001). Biosorption, as a means of removing toxic heavy metals, is especially suited as a ‘polishing’ wastewater treatment step as the quality of the outcome is close to the level of potability. From initial metal concentrations of 1 – 100 mg·L-1 it can be reduced to < 0.01 – 0.1 mg·L-1, especially in packed bed flow-through applications (Naja et al. 2010). Biofilm formation is one important characteristic if bacteria are to be utilized in heavy metal removal through biosorption. Biofilm’s most essential constituent with ion sequestration capability is extracellular polysaccharides or exopolysaccharide, which can exist either as capsule or slime (Gupta and Diwan 2017).

This study was conducted with the aim of isolating bacteria from mined-out soil from Mogpog, Marinduque, screening them for heavy metal tolerance and biofilm formation and using them in removing heavy metals in solution through biosorption.

Link to the Original & Complete Publication:

ACKNOWLEDGMENT

This research was supported by funds from the Philippine Council for Industry, Energy and Emerging Technology Research and Development Department of Science and Technology, Department of Science and Technology (PCIEERD-DOST) and partly by Fostering Educational and Environmental Development (FEED), Inc.

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