Leachate toxicity assessment and bioremediation of leachate contaminated soil / Emenike Chijioke Uche

Chemical evaluations and characterization had often served as the commonly adopted options for assessing the potential impact of pollutants, which at the same time provide insight into the possible remediation technologies. However, heterogeneous substances may not be best studied in aforementioned forms because of the varied characteristics and concentrations of the discrete components. Leachate which is the liquid by-product of waste decomposition in landfills or dump sites is one such heterogeneous fluid that can easily pollute the environment (terrestrial and aquatic). With increase in waste generation in Malaysia, leachate production becomes inevitable especially as landfilling is the ultimate predominant waste disposal option. An average of 300,000 L of leachate is produced daily from each landfill and there are over 200 landfills in operation. Considering the high distribution of waste disposal sites in Malaysia, the study was designed to characterize leachate from the different landfill types in relation to their operational status. It aimed to assess the mortality effects of the leachate on aquatic life such that leachate toxicity index can be proposed. Similarly, the study was undertaken to investigate a possible accumulation of heavy metals in fish species due to leachate pollution and at the same time adopting a bioremediation option that will help remove the heavy metal that percolate in the soil due to leachate leaks, as a way of preventing heavy metals from getting to nearby surface water. Various methods adopted in the study ranged from the physico-chemical characterization of leachate, acute toxicity exposure, histopathology, to microbial characterization and bioaugmentation of leachate contaminated soil. Microsoft Excel, SPSS, EPA Finney’s Probit and Datafit were statistical tools used in the study. Some similarities were found among the characterized leachate samples. At 482 – 51,200 mg/L COD and 127 – 27,000 mg/L BOD5, the organic concentrations of the landfills were above the landfills’ discharge limits in Malaysia regardless of the landfill type. Ammonical-nitrogen was present in all the landfills and the highest value (880 mg/L) was obtained in the non-active sanitary landfill, whereas concentrations of heavy metals were highest (540 mg/L) in the active sanitary landfill leachate. The acute toxicity test revealed that LC50 as low as 1% v/v of the raw leachate was possible and showed that mortality and the corresponding Fish Leachate Toxicity index (FLLTI) decreased in the order of non-active sanitary (5.46), active sanitary (3.87), non-active non-sanitary (1.76) and the active non-sanitary (1.28) landfills, respectively. Bioaccumulation study revealed that about 3.2 μg/g and 2.1 μg/g of Zn and Fe, respectively were found in the fish after exposure to leachate pollution for 96 hours, as against 0.21 μg/g and 0.8 μg/g of the same heavy metals obtained in the control experiment (non-exposed fish), respectively. Similarly, tissue analysis of fish showed pale stains on the cellular compartments of the gills and liver. Microbial characterization of the leachate polluted soil indicated that regardless of the toxic effect on the environment, some bacteria species can survive namely Bacillus sp., Pseudomonas sp., Lysinibacillus sp., Rodococcus sp., Acinetobacter sp., Microbacterium sp., Brevundomonas sp., Stenotrophomonas sp., and Flavomonas sp. Bioaugmenting the polluted soil with different treatments (A,B,C) formed from the combination of the microbes showed that the highest heavy metal removal was achieved when Bacillus sp., Lysinibacillus sp. and Rodococcus sp. were combined as compared to other treatments (P < 0.05). Cu (86%), Zn (73%), Pb (70%), Fe (67%) and Mn (64%) were removed after 100 days of biomonitoring. The least heavy metal removal rate constant was observed for Cd (K = 0.0053 day-1). Therefore, the study concludes that raw landfill leachate in Malaysia is toxic to these fish species, yet the varied impact of leachate is a reflection of the variation in the heterogeneous nature of leachate across different landfills rather than differences in exposed fish species/types. Also, the use of isolated microbes from leachate contaminated soil to bioaugment the polluted soil is a potential approach for optimal removal of heavy metals from leachate polluted soil

BIOTRANSFORMATION AND REMOVAL OF HEAVY METALS: A REVIEW OF PHYTO AND MICROBIAL REMEDIATION ASSESSMENT ON CONTAMINATED SOIL

Environmental deterioration is caused by a variety of pollutants; however, heavy metals are often a major issue. Development and globalization has now also resulted in such pollution occurring in developing societies, including Africa and Asia. This review explores the geographical outlook of soil pollution with heavy metals. Various approaches used to remedy metal-polluted soils include physical, chemical, and biological systems, but many of these methods are not economically viable, and they do not ensure restoration without residual effects. This review evaluates the diverse use of plants and microbes in biotransformation and removal of heavy metals from contaminated soil. Mechanisms on how natural processes utilizing plants (phytoremediation) and microorganisms (bioremediation) remove or reduce heavy metals from soil at various levels are presented. This review concludes that remediation technologies are necessary for the recovery of metal-contaminated environments and the prevention of continuous environmentally toxic impacts on living organisms.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Growth kinetics and biodeterioration of polypropylene microplastics by Bacillus sp. and Rhodococcus sp. isolated from mangrove sediment

Interest in the biodegradation of microplastics is due to their ubiquitous distribution, availability, high persistence in the environment and deleterious impact on marine biota. The present study evaluates the growth response and mechanism of polypropylene (PP) degradation by Bacillus sp. strain 27 and Rhodococcus sp. strain 36 isolated from mangrove sediments upon exposure to PP microplastics. Both bacteria strains were able to utilise PP microplastic for growth as confirmed by the reduction of the polymer mass. The weight loss was 6.4% by Rhodococcus sp. strain 36 and 4.0% by Bacillus sp. strain 27 after 40 days of incubation. PP biodegradation was further confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy analyses, which revealed structural and morphological changes in the PP microplastics with microbial treatment. These analyses showed that the isolates can colonise, modify and utilise PP microplastics as carbon source

Post-War waste composition: Household waste management in Misrata City, Libya

Waste generation and its composition reflect activities of a society, due to the fact that it is driven by socio-economic interactions, political structure, and social security. However, changes to waste composition may go unnoticed, except where a database on household solid waste (HSW) is available. Libyan cities were devastated by the scourge of war due to the "Arab spring". This necessitates planning and development to tackle waste management. This study aims to determine the composition of household solid waste in Misrata, Libya, to generate waste stream data that eludes most post-war cities in North Africa and Middle East, which can be used to plan and subsequently manage waste collection services, treatment options, and disposal methods. Discrete classification and direct measurement of HSW from selected families (30) in Misrata were utilized to assess waste composition and changes across households. 400 questionnaires were distributed to residents to determine public perception and its correlation to waste composition. The results confirmed that the highest amount of HSW generated was organic waste, which accounts for 52 %, followed by 20.7%, 16% and 5.9% generated from miscellaneous waste, plastics, and paper wastes, respectively. Metals and glass reported the lowest HSW components, at 3.9% and 1.5%, respectively. The survey component of the study indicated that more than 70% of the respondents claimed that recyclable items are increasing, especially plastics, due to changes in life style and income