Municipal Waste Dumpsite Research Articles

Molecular and biochemical characterization of solid waste biodegrading microbes isolated from municipal waste dump site

Solid waste dump site-based pollution is one of the colossal health concerns globally due to presence of cellulose, starch, protein, and lipids, which is a perfect nutrient waste for the development of biodegrading potential microbes. The current study aimed to determine the productive microorganisms for waste biodegradation. Ten samples were collected from different areas of Karachi waste dump sites. The identification and characterization of isolates were done by morphological and biochemical tests. The isolated microbes were qualitatively screened for the action of making industrially key bio-enzymes. The potential enzymes producing microbes were subjected to waste degradation test for 90 days. Changes of odor, color and weight loss of decomposing garbage were noted. The highest degradation ability in term of weight loss was shown by Aspergillus (SSI14) and Bacillus (SSI6). Four metals (zinc sulphate, cadmium chloride, copper sulphate and iron sulphate) were chosen for the purpose of metals tolerance test and minimum inhibitory concentration (MIC) of the isolated microbial strains. Current study reported that Zn was found to be more lethal in in comparison to Cu and Fe. Molecular identification of the isolated microbes was done by polymerase chain reaction. The microbial strains were characterized by the polymerase chain reaction (PCR) followed by confirmation of product by agarose gel electrophoresis. The findings can be served as baseline data to develop microbial apparatus for biodegradation and management of solid waste.

Leaching Test Protocols to Evaluate Contaminant Response of Nano-Calcium Silicate–Treated Tropical Soils

The current study deals with the interaction of toxic metals with soils by conducting a series of leaching tests on four kaolinitic soils procured from locations with varying pollution levels, such as a pristine location, vicinity of steel mill works, battery works unit, and an abandoned municipal waste dump site. The procured soils were spiked with 3,000 mg/kg of toxic metals, lead (Pb), and nickel (Ni) to understand the contaminant transport. An innovative amendment, such as synthesized nano-calcium silicate (NCS), was also mixed with the soils for toxic metal immobilization. Leaching tests. such as the toxicity characteristic leaching procedure (TCLP), extended TCLP, and caged TCLP, were conducted on soil samples. These tests were successful in predicting the interactive behavior of the composite mix containing soil, NCS, and toxic metals, comprehensively. The vulnerability of soils based on TCLP can be expressed in the order of Soil C > Soil D > Soil B > Soil A. These results were concurrent with extended TCLP, wherein the response of these composites at various pH levels was presented. Caged TCLP quantified the leaching rate for different mixtures, and it was found that the leaching rate for virgin soils reduced from 1.3 to 0.075 cm/yr after the NCS amendment. The addition of NCS resulted in the agglomeration and aggregation of soil particles. This increased the density and reduced the void spaces of the soil–nano mix, thereby encapsulating the toxic metals permanently within its interstices. The highest attenuation was observed for Pb2+ compared with Ni2+ for all the mixtures considered. Thus, leaching tests can be considered a prospective short-term technique for monitoring polluted soil media compared with tedious and time-dependent column studies.

A baseline study of meso and microplastic predominance in pristine beach sediment of the Indian tropical island ecosystem

The global presence and prevalence of microplastic have moved microplastic from an emerging pollutant to a persistent contaminant. Microplastic prevails in almost all spheres of the environment viz. terrestrial, marine and atmosphere the globe abundantly. The prevalence and toxic effects on marine organisms have been studied around the world but the studies are limited to the coastal regime of the Andaman and Nicobar Islands (ANI). This study aims to record microplastic prevalence on the tourist beaches of Port Blair, ANI. Three coastal stations namely Cove beach, Quarry beach and Wandoor beach were examined in detail in this regard. Microplastics in the form of lines, fragments, pellets, foams and fibres were found at the sampled sites. Wandoor beach recorded the highest microplastic particles ranging from 105–475 particles kg−1 of sediment with the mean value of 249.82 ± 105.78 particles kg−1. Quarry beach near the municipal waste dumpsite showed the lowest of 72.5–222.5 particles kg−1 with a mean value of 135.625 ± 62.83 particles kg−1. The polymeric forms found were High-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP) and polyethylene terephthalate (PET). This study revealed microplastic input from municipal dump waste near the beach. Fourier Transform Infrared spectroscopy (FTIR) revealed the presence of a new type of polymer namely plasta zinc in the beach sediment, which possibly could be a nanoplastic. Its presence reveals the biological enzymatic degradation of microplastic occurring in the marine environment. Further investigations are required to determine the factors influencing the prevalence of microplastic, its toxic effects on marine habitat and microplastic degradation mechanisms in the marine habitat.

REGRESSION ANALYSIS OF THE LEAD CONCENTRATION IN THE SOIL AT THE DISTANCE FROM THE LANDFILLS OF SOLID MUNICIPAL WASTE

In recent years the total area of the solid municipal waste landfills and dumpsites, including the overloaded ones, which violate the norms of ecological safety and are the objects of intensive ecological loading, that may cause the pollution of the environment with chemical substances, contaminating soil, in particular with the lead has greatly increased. Determination of the regression dependence of lead concentration in the soil on the distance to solid municipal waste landfills is an important scientific-technical problem. Objective of the research is to determine the regressive dependence of lead concentration in the soil on the distance to solid municipal waste landfills. During the research the method of regressive analysis of the results of single-factor experiments and other pair dependences with the selection of the rational type of function from sixteen most widely spread variants by the criterion of maximum value of the correlation factor has been used. Regression was performed on the base of the linearizing transformations, which enable to reduce the nonlinear dependencein to linear one. Determination of the coefficients of the regression equations was carried out by means of the least squares method, applying the developed computer program "RegAnaliz", protected by the Certificate of the State registration of the rights to the copyright object. Adequate regressive power dependence of the lead concentration in the soil on the distance to solid municipal waste landfills was obtained, the dependence can be used for the determination of the level of chemical pollution of the soil with lead. Graphic interpretation of the lead concentration dependence in the soil on the distance to solid municipal waste landfill was constructed, it enables to illustrate this dependence and show the coincidence of the theoretical results with actual results on the level of 0.93493. It is established that the distance from the landfill of solid municipal waste, where the lead pollution of the soil does not exceed the background level(boundary of mild contamination area), is 526 m.

Soil Quality of Farmlands Close to Municipal Waste Dumpsites

Soil samples collected from some farmlands very close to municipal dumpsites located in Jos, Plateau State were studied to assess the soil quality of the farms with respect to the soil physico-chemical properties and heavy metal concentration. The results show that the soil samples from the farm and control sites are loam while the dumpsites are sandy (contained sand fraction >85.0%). Soil mean pH varied between 5.902±0.02 in Zaria road control soil to 7.16±0.22 in Zaria road farm. While the CEC (cmol kg-1) in the farm soils (14.35±0.66, 12.44±0.20) are higher than that of the control sites (8.35±0.75, 7.41±0.10) and consistent with the dumpsites (23.60±0.02, 21.18±0.01), the percentage organic matter in all the study sites are far above the average level by FAO for agricultural soil. The concentrations of all the metals (Zn, Co, Cr, Pb, As, Cd and Cu) in the dumpsites and farm soil are higher than those of the control, permissible limits of WHO, EU and the DPR target for metals except for Cd. Zn, Co, Pb and Cu were predominant in the sites while As and Cd had low concentrations. With the exception of Zn and Cr in the farm soils, all the heavy metals had anthropogenic inputs of >50%. The index of geoaccumulation results for the metals showed moderate pollution of the farm soils with Cr, Pb, As, Co and Zn; and a strong pollution with respect to Cd. The continuous dumping of waste in these areas may therefore constitute a serious threat to the soil qualities of the nearby farms

Environmental Implications of Municipal Dump Site on Soil Nitrogen in Calabar Metropolis, Nigeria

Organic matter exhibit strong variations in nitrogen retention and transformation cycle in soil. However, nitrogen could be altered by seasonal variations, leading us to hypothesize that the open municipal waste dump site in Calabar exposed to dry and wet season could alter nitrogen dynamics in that soil. A total of sixty (60) composite soil samples were collected at different landscape positions (summit crest, shoulder slope, toe slope, interfluve slope, valley floor) of a municipal dump site and a control (no refuse area) during the dry and wet seasons in Calabar and analyzed to ascertain the effects on forms and status of soil nitrogen. The soils were loamy sand across the study location with pH values of 4.50, 7.00, 6.70, 7.30, 5.00, 7.30 (dry season) and 5.00. 7.30, 7.00, 7.40, 5.90, 7.40 (wet season) for the control, summit crest, shoulder slope, toe slope, interfluve slope and valley floor accordingly. Values obtained for total nitrogen (N) from the study site were generally low (<0.21 %), with values for dry season slightly higher than the wet season. NH4+ recorded higher content in wet than in dry season with values ranging between 12.11-14.11 mg/kg (control), 14.60 - 15.90 mg/kg (Summit crest); 18.25 - 20.05 mg/kg (Shoulder slope), 18.30 - 20.20 mg/kg (Toe slope), 12.30 - 14.00 mg/kg (Interfluve slope) and 9.24 -11.07 mg/kg (Valley floor). The Shoulder and toe slopes recorded the highest NH4+ concentration in the wet season. N02- contents documented for the control site were within the ranges of 2.78- 3.20 and 3.22-3.62 mg/kg while the dumpsite had values between 2.49-3.45 and 2.98 -3.22 mg/kg was observed for the shoulder position, the toe slope contained between 2.30-2.75 and 2.70 -2.82 mg/kg, the inter fluve slope had similar ranges of 2.32-2.90 and 2.70-3.08 mg/kg, and the valley floor 2.45-2.60 and 2.78-2.98 mg/kg. N02- values were higher for the wet than dry season. NO3- nitrogen was observed to be excessive across the dumpsite with the highest values > 80 mg/kg obtained at the valley floor. The NO3- values were higher in dry season across the all the landscape positions than in the wet season. The values were equally higher for the dumpsite than the control. It was observed that the dumpsite soils contend excessive NO3- which could be converted to nitrous oxide (N2O) thus contributing to green house (GHG) emissions. It was also noted that seasonal variation did not significantly affect the N content at the different landscape positions of the municipal dumpsite in Calabar. It is highly recommended that municipal waste be sorted and the organic materials composted to harness the rich NO3- content as observed in this research.
 
 Received: 22 September 2021 / Accepted: 25 October 2021 / Published: 5 November 2021

Spatial trends of chlorinated paraffins and dechloranes in air and soil in a tropical urban, suburban, and rural environment

There are large knowledge gaps concerning environmental levels and fate of many organic pollutants, particularly for chemicals of emerging concern in tropical regions of the Global South. In this study, we investigated the levels of chlorinated paraffins (CPs) and dechloranes in air and soil in rural, suburban, and urban regions in and around Dar es Salaam, Tanzania. Samples were also collected near the city's main municipal waste dumpsite and an electronic waste (e-waste) handling facility. In passive air samples, short chain CPs (SCCPs) dominated, with an average estimated concentration of 22 ng/m3, while medium chain CPs (MCCPs) had an average estimated concentration of 9 ng/m3. The average estimated air concentration of ∑dechloranes (Dechlorane Plus (DP) + Dechlorane 602 + Dechlorane 603) was three to four orders of magnitudes lower, 2 pg/m3. In soil samples, MCCPs dominated with an average concentration of 640 ng/g dw, followed by SCCPs with an average concentration of 330 ng/g dw, and ∑dechloranes with an average concentration of 0.9 ng/g dw. In both air and soil, DP was the dominating dechlorane compound. Urban pulses were observed for CPs and dechloranes in air and soil. CPs were in addition found in elevated levels at the municipal waste dumpsite and the e-waste handling facility, while DPs were found in elevated levels at the e-waste handling facility. This suggests that waste handling sites represent important emission sources for these pollutants. Investigations into seasonal trends and environmental fate of CPs and dechloranes showed that monsoonal rain patterns play a major role in governing air concentrations and mobility, particularly for the less volatile MCCPs and dechloranes. This study is the first to report levels of CPs in air from sub-Saharan Africa, and DP, Dechlorane 602, and Dechlorane 603 in soil from sub-Saharan Africa.

Impact of Okhla, Bhalswa and Ghazipur Municipal Waste Dumpsites (Landfill) on Groundwater Quality in Delhi

Rapid urbanization, increasing prosperity, economic development coupled with changing lifestyle has produced a tremendous generation of waste in huge quantity. The dumping of this huge quantity of partially segregated waste has become a public health and environmental concern. According to an estimate, more than 9500 tons per day (TPD) of MSW (Municipal solid waste) is generated in Delhi and about 60% of waste is transported to these three-active landfills in order of maximum in Bhalswa followed by Ghazipur and Okhla landfill sites which are non-scientific landfill and less than 40% were transported to composting plant and waste to energy plant. These waste dump sites have finished their commissioned date and crossed the permissible height and come under matured landfill (old). Dumping of unsegregated waste in these landfills contribute long-term threat to groundwater as various parameter such as inorganic, organic and heavy metal liberate from leachate of unsegregated solid waste and concentration varies with season. Soil contamination, air pollution and various other environmental, health and social impacts in the vicinity of these landfills are found to be connected with uncontrolled dumping of waste. The study reported that, till date in Delhi, there is no single landfill which is controlled and provides with baseliner or proper cover. All three active landfill still received solid waste beyond their capacity without any attention to waste segregation. Impact of landfill leachate on groundwater revealed by presences of high concentration of various parameters like Chloride, Nitrate, Sulphate, Ammonium, Phenol, Iron, Zinc and Chemical oxygen demand in assessed which showed that quality of groundwater is significantly affected by the percolation of landfill leachate. The main problem of the landfill is the generation of toxic leachate and gases which finally end their life in groundwater and environment and ultimately reach to human and damage aquatic life present in water. On the other hand emission of greenhouse gases lead to the risk of fire and also cause global warming. Presently NGT had warned officer of these three landfills of Delhi to remediate landfill. There is an urgent need of leachate collection system and treatment facilities and gas trapping technologies at this landfill for energy generation and to protect the contamination of groundwater.

Aerobic degradation of decabrominated diphenyl ether through a novel bacterium isolated from municipal waste dumping site: Identification, degradation and metabolic pathway

In the present study, a novel bacterium capable of degrading BDE-209 aerobically was isolated from a municipal waste dumping site and identified as Bacillus tequilensis strain BDE-S1 through 16S rRNA gene sequencing. A correlation between BDE-209 and bromide concentration, COD, TOC, and cell biomass was established. 65% of 50 mg/L initial concentration of BDE-209 was degraded within eight days of incubation by BDE-S1 strain. Two hexa, two penta, one tetra-BDE congener, and benzamide were detected as metabolites. The bromide release, COD, TOC and cell biomass were found to be significantly correlated parameters with BDE-209 degradation. Based on the metabolite analysis, ortho and meta debromination, cleavage of diphenyl ether bond and ring-opening were suggested as possible degradation pathways. This is the first study demonstrating the use of indigenously isolated Bacillus tequilensis strain BDE-S1 for aerobic degradation of BDE-209, which could provide new comprehension for bioremediation of PBDEs from contaminated environments.

Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in municipal waste dumping site, incinerator and brick kiln residues: evaluation for potential risk assessment

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) consist of a group of organohalogenated compounds which are ubiquitous, anthropogenic, toxic and persistent organic pollutants. Human exposure to PCDD/Fs is associated with severe health risks. In the current study, levels of PCDD/Fs were determined in soil from municipal waste (MW) dumping site and ash residues from hospital waste incinerators (HWIs) and brick kilns (BKs) in Peshawar, Khyber Pakhtunkhwa (KP) Province, Pakistan. A total of 17 congeners (7 PCDDs and 10 PCDFs) were quantified using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) 6890 Series (Agilent, USA). The PCDD/Fs contamination levels in the studied samples followed an order of HWIs > BKs > MW dumping site. Among HWIs, highest toxicity values of 2343 ng international toxicity equivalency factors (I-TEQ)/kg and 2138 ng World Health Organization-toxicity equivalents quantity (WHO-TEQ)/kg were observed for Khyber Teaching Hospital (KTH), while toxicity values for Hayatabad Medical Complex (HMC) were found to be 1493 ng I-TEQ/kg and 1416 ng WHO-TEQ/kg, respectively. The TEQ values were found in order of HWIs > BKs > MW site. Potential for both non-cancer and cancer risk (CR) in three pathways was found in order as ingestion > dermal > inhalation. Based on the finding it can be inferred that the onsite workers and general public exposed to such levels are under potential risk for both carcinogenic and non-carcinogenic risk.

Health Risk Assessment of Natural Radioactivity in Wasteland Soils in Okakarara, Namibia..

Human activities such as waste disposal tend to impact negatively on the environment. Some waste products are associated with elevated levels of natural radioactivity. It was therefore, the aim of the study to investigate the health risk associated with natural radioactivity from Okakarara municipal waste dumpsite. In this study, gamma spectrometric analysis was used to determine the activity concentrations of 226Ra, 232Th and 40K in 18 soil samples. From these activity concentrations, some radiological parameters were calculated. The average activity concentrations of 226Ra, 232Th and 40K in (Bq.kg-1) were 15.45±0.47, 18.00±0.55, and 215.73±4.29, respectively. The average Raeq value was 57.80±0.98 Bq.kg-1. In all the samples, Raeq values were found to be lower than the worldwide value of 370 Bq.kg-1. The absorbed dose rate was found to be 27.00±0.44 nGy.h-1, whereas an average value of 0.03 mSv.y-1 for AEDE is noted, which is less than 0.48 mSv, the worldwide average. The Annual Gonadal Dose Equivalent (AGDE) was 190.89 μSv.y-1, a value less than the world average of 298 μSv.y-1. The average values of the Representative Level Index (RLI) and the External Hazard Index (Hex) was found to be 0.43 and 0.16., respectively. These indices were less than unity. The average value of the excess lifetime cancer risk (ECLR) was 1.16 x 10-4. This value was lower than the internationally acceptable limit of 2.9 x 10-4. From these results it can be concluded that natural radioactivity from the wasteland area of Okakarara was not an issue of health concern.

Antimicrobial sensitivity profiling of bacterial communities recovered from effluents of municipal solid waste dumping site

The diversity of antibiotic-resistance bacteria (ARB) from the effluents of Aizawl city municipal waste dumping site was studied using a culture-dependent method. The present study molecularly identified 73 isolates that were differentiated into three phyla (Proteobacteria, Actinobacteria, and Firmicutes) belonging to 17 family and 22 genera. Bacillus constitutes the most dominant genus comprising 16% of the total isolates. The topology of the phylogenetic tree differentiates them into five major clades. Corynebacterium and Rhodococcus which are morphologically alike were clustered together and the Gram-positive bacteria such as Staphylococcus, Bacillus, and Lysinibacillus formed a separate cluster. Antibiotic resistance of the identified bacterial isolates was performed using 19 different antibiotics. Among the isolates, 70 of them found resistant to polymixin B and nalidixic acid and 10 isolates exhibited resistance to 15 tested antibiotics. The present study revealed that bacteria with antibiotic resistance are extensively distributed in the effluents of the dumping site and may serve as a significant reservoir for the spreading of antibiotic resistance to opportunistic pathogens.

DEPENDENCE OF THE LEVEL OF MICROBIOLOGICAL POLLUTION WITH GENERAL COLI GROUP BACTERIA OF THE SURFACE WATER ON THE DISTANCE TO THE SOLID MUNICIPAL WASTE LANDFILL

In recent years the total area of solid municipal waste landfills and dump sites, including overloaded, which violate the norm of ecological safety and are the objects of the intensive ecological loading has considerably increased. This may cause  the pollution of the environment by the microorganisms (colibacilli bacteria, streptococci, staphylococci and ascarids), causing bacteriological contamination of the soil and ground water. Determination of the regression dependence of the level of the microbiological pollution by general coli group bacteria of the ground water on the distance to the solid waste landfill is an urgent scientific-engineering problem. Aim of the research is to determine the regression dependence of the level of microbiological pollution with the general coli group bacteria on the distance to the solid municipal waste landfill. In the process of the research the method of the regression analysis of the results of single-factor experiments and other paired dependences with the selection of the rational type of the function from sixteen most widely spread variants by the criterion of the maximum value of the correlation factor is used. Regression was performed on the base of the linearized transformations, which enable to reduce the non-linear dependence to the linear one. Determination of the coefficients of the regression equations was carried out, applying the method of the least squares by means of the developed computer program "RegAnaliz", protected by the certificate of the State Registration of the rights to the copyright object. Adequate regression dependence of the level of microbiological pollution with the general coli group bacteria of the surface water on the distance to SMW landfills was obtained , the given dependence is used for the determination of the safe distance for the location of SMW landfills from the sources of the drinking water by the index of the level of microbiological pollution with the general coli group bacteria of the surface water. Graphic interpretation of the dependence of the level of microbiological pollution with the general coli group bacteria of the surface water on the distance to the solid waste landfill is constructed, it enables to illustrate this dependence and show the coincidence of the theoretical results with the actual results on the level of 0.99996.

Biodegradation of Unpretreated Low-Density Polyethylene (LDPE) by Stenotrophomonas sp. and Achromobacter sp., Isolated From Waste Dumpsite and Drilling Fluid.

Exploring the catabolic repertoire of natural bacteria for biodegradation of plastics is one of the priority areas of biotechnology research. Low Density Polyethylene (LDPE) is recalcitrant and poses serious threats to our environment. The present study explored the LDPE biodegradation potential of aerobic bacteria enriched from municipal waste dumpsite and bentonite based drilling fluids from a deep subsurface drilling operation. Considerable bacterial growth coupled with significant weight loss of the LDPE beads (∼8%), change in pH to acidic condition and biofilm cell growth around the beads (CFU count 105–106/cm2) were noted for two samples (P and DF2). The enriched microbial consortia thus obtained displayed high (65–90%) cell surface hydrophobicity, confirming their potential toward LDPE adhesion as well as biofilm formation. Two LDPE degrading bacterial strains affiliated to Stenotrophomonas sp. and Achromobacter sp. were isolated as pure culture from P and DF2 enrichments. 16S rRNA gene sequences of these isolates indicated their taxonomic novelty. Further biodegradation studies provided strong evidence toward the LDPE metabolizing ability of these two organisms. Atomic Fore Microscopy (AFM) and Scanning Electron Microscopy (SEM) revealed considerable damage (in terms of formation of cracks, grooves, etc.) on the micrometric surface of the LDPE film. Analysis of the average roughness (Ra), root mean square roughness (Rq), average height (Rz), maximum peak height (Rp), and maximum valley depth (Rv) (nano-roughness parameters) through AFM indicated 2–3 fold increase in nano-roughness of the LDPE film. FTIR analysis suggested incorporation of alkoxy (1000–1090 cm–1), acyl (1220 cm–1), nitro (1500–1600 cm–1), carbonyl (1720 cm–1) groups into the carbon backbone, formation of N-O stretching (1360 cm–1) and chain scission (905 cm–1) in the microbially treated LDPEs. Increase in carbonyl index (15–20 fold), double bond index (1.5–2 fold) and terminal double bond index (30–40 fold) confirmed that biodegraded LDPEs had undergone oxidation, vinylene formation and chain scission. The data suggested that oxidation and dehydrogenation could be the key steps allowing formation of low molecular weight products suitable for their further mineralization by the test bacteria. The study highlighted LDPE degrading ability of natural bacteria and provided the opportunity for their development in plastic remediation process.

Elucidation of coding gene and characterization of alkaline metallo-keratinase produced by acidophilic Bacillus sp. Okoh-K1 grown on chicken feather

The poultry processing industry generates a huge amount of feathers as waste. The feathers are recalcitrant to degradation, and are fraught with environmental problems. Therefore, the microbial utilization of feather biomass for the production of valuable products represents sustainable development. In this study, a keratinolytic bacteria previously isolated from a municipal waste dumpsite, and identified as Bacillus sp. Okoh-K1 was used to produced keratinase in a basal medium formulated with chicken feathers. The keratinase produced was characterized, and the gene coding for the enzyme elucidated. The optimized physico-chemical conditions were 1% (w/v) chicken feather, 0.1% (w/v) lactose, pH (4.0–6.0), temperature (30 °C) and agitation speed (150 rpm). The kinetics of keratinase production by Bacillus sp. Okoh-K1 in an optimized fermentation medium showed maximum extracellular keratinase activity of 2350.09 ± 107.99 U/mL after 48 h of fermentation. The keratinase (KerBOK1) showed optimal catalytic activity at pH and temperature of 8.0 and 60 °C, respectively; with remarkable pH and thermal stability. Ethylenediaminetetraacetic acid and 1,10-phenanthroline both inhibited the activity of KerBOK1; thus, suggesting a metallo-type of keratinase. Furthermore, the enzyme showed considerable stability upon mixture with reducing agents, organic solvents, surfactants and laundry detergents. The putative keratinase gene (kerBOK1), with band size and G+C contents of 1104 bp and 36.1% respectively, showed >90% of sequence homology with keratinase gene of Bacillus cereus group. The findings from this study suggest that both Bacillus sp. Okoh-K1 and the keratinase possess immense prospects for biotechnology and industry.

Evaluation of soil contamination status around a municipal waste dumpsite using contamination indices, soil-quality guidelines, and multivariate statistical analysis

Indiscriminate dumping of municipal solid wastes in and around most cities in Nigeria coupled with improper waste management of the available dumpsites posed a major threat of pollution in the surrounding soils. This study assesses the concentration of heavy metals and contamination status of soils around a municipal waste dumpsite located at Arufe street, Omuooke-Ekiti, SW, Nigeria using contamination indices, soil-quality guidelines, and multivariate statistical analysis. Soil samples from different depths were taken from the center of the dumpsite and surroundings at different distances and directions. The concentration of the metals in soils taken at depth of 0–50 cm (topsoil) was significantly higher than in soils taken at depth of 50–100 cm(subsoil). The mean concentrations of heavy metals in the topsoil showed the following order Fe > Cr > Mn > Zn > Pb > Cu > Ni while those of major cation followed the order Ca > K > Na > Mg. Exceptionally high concentration of the heavy metals compared with the background values were found at the center or close to the center of the dumpsite, which indicates an anthropogenic contribution. Compared with the adopted soil-quality guideline, only Cr and Pb showed concentrations well above the threshold value. The mean enrichment factor of all the heavy metals except Cr and Pb were Pb > Mn > Zn > Fe > Cu > Ni. The modified degree of contamination values was found to be mainly less than 1.5 except at the center of the dumpsite. The ecological risk index (ranged 4.37–505.55) implies low to considerable risk for the dumpsite. The significant positive correlations observed among heavy metals and the major cations indicate that these metals probably have similar sources and properties. The PCA reveals that the metals have a strong association and may have a similar source. The cluster analysis categorized the sampling points into three major groups of spatial similarities. The metals concentration combined with the contamination indices and soil-quality guidelines indicated that the soils in and around the dumpsite are polluted or being polluted because of the dumpsite.

Municipal waste dumpsite: Impact on soil properties and heavy metal concentrations, Sunyani, Ghana

The use of soils around dumpsites in rural and urban areas in Ghana is common for food production especially vegetables. However, most people use such soils without knowledge of the risk of heavy metal uptake by plants. Therefore, the evaluation of heavy metal contamination is an important component of risk assessment at waste dumpsites. Hence, this study was conducted in Sunyani municipality to determine the risk of heavy metal pollution and physicochemical properties of soils at a waste dumpsite. Fifteen (15) soil samples (5 from each zone) were collected from a depth of 0–30 cm depth within the 3 demarcated zones of the dumpsite namely; Top-site, Dump-site, and Down-site. Physicochemical properties and heavy metals (e.g. lead, zinc and cadmium) were analysed to determine their concentrations in the collected soil samples. From the result, significant differences (p < 0.05) in soil chemical properties were observed and their levels ranked as dump-site > down-site > top-site. The concentration of the metals ranked as Fe > Pb > As > Zn > Cd at the dumpsite. The results revealed that the soil at the dumpsite is heavily contaminated with Fe (> 30 mgkg−1) as opposed to less than 0.55 mg kg−1 for the remaining heavy metals (As, Cd, Pb and Zn). However, heavy metals contamination at the various sampling locations of the dumpsite were within the permissible limits recommended by FAO/WHO. There is the need for regular monitoring and decontamination of the dumpsite before use for agricultural activities.

IMPACT OF SOLID WASTE DUMP-SITES ON GROUNDWATER QUALITY IN BENIN CITY, NIGERIA

Municipal waste dumpsites contain pollutants which are either water-solution or are capable of being moved along the path of water during percolation through the soil to groundwater. This study was therefore carried out to investigate the impact of solid waste dump-sites in Benin City on the receiving groundwater quality. Four stations were chosen for this study, with each station located within one Local Government Area. These stations were dump-sites at Ikhueniro (station 1), Costain (station 2) and Ugbioyoko (station 3). Omaghe (station 4) was used as the control station without waste dumpsite. Soil samples were collected at three distances from the dump-sites of 0-50m, 50-100m, &gt;100m at 0-30cm depth of top soil and analyzed while the boreholes used were within 120m radius from the dump-sites. This investigation spanned from July 2011 to December 2011. Results showed that water samples were found to be enriched with heavy metals (Fe, Mn, Zn, Cu, Cr, Pb, Ni and V) more than the control water sample; these were however within WHO and FMEnv. regulatory limits for drinking water. The mean pH values of the sampled water fluctuated between 4.50 and 5.57 and were not within the WHO and FMEnv. regulatory limits of 6.5 to 8.5 set for drinking water. ANOVA revealed a highly significant difference (p &lt; 0.01) between the means of the following water parameters; Ca, Na, K, Mg, electric conductivity, Salinity, HCO3, and total soluble solids. The Kruskal-Wallis Test revealed that aerobic bacterial count was significant (p &lt; 0.05) with the highest mean value in station 1 (17.17 x102 cfu/ml) and lowest mean value in station 4 (6.00x102 cfu/ml). Seasonal pattern of variations was observed for water samples examined.

Determination of Elemental Composition of Soil Samples from Selected Dumpsites in Nasarawa, Kogi and Niger States, Nigeria

The growing dominance of urban environment with heavy metals through natural and anthropogenic depositions and the potentially adverse health implications following environmental contaminations have focused attention on the disposal of municipal and industrial wastes. This study employed analytical procedures to investigate the concentrations of chromium, iron, copper, zinc, manganese and aluminium at the municipal waste dump site of the study areas. Soil samples were randomly collected from different waste dumpsite across Nasarawa, Kogi, and Niger states and an undisturbed soil 100m away from the dumpsites was chosen as the control. From the result obtained, it was observed that the metals in all dumpsite types followed the order: Mn&gt;Fe&gt;Zn&gt;Cu&gt;Cr&gt;Al. Mn had the highest mean concentration which was recorded in Bida, Borgu and Minna in Niger State while Al was the least detected in all the dumpsites with the lowest mean concentrations (5.7±0.96) recorded in Borgu. Mean concentration of all the metals at the dumpsites was higher than at the control which means there is an anthropogenic contribution from the environment. The concentrations of the heavy metals were generally lower than their respective guideline values for the protection of human and environmental health. However, with prolong practice of dumping refuse at these sites; concentrations of the heavy metals may increase above the recommended limits. Therefore, we recommend that further research be carried out on the heavy metals concentration of the waste materials to identify those that are potential sources of soil contamination to suggest appropriate treatment and disposal methods.

Engineering a bioluminescent bioreporter from an environmentally sourced mercury-resistant Enterobacter cloacae strain for the detection of bioavailable mercury.

Escherichia coli is the conventional choice as the host strain for whole-cell bioreporter construction due to its well-understood genetics and well-established cloning protocols. However, for real-world environmental biosensing applications, it is often beneficial to use a bacterial strain derived directly from the environment under study to better ensure chemical target specificity and optimal response time. The aim of this study was to develop a whole-cell bioreporter for detection of bioavailable mercury by replacing E. coli with a wild-type bacterial host derived from a soil environment. In this study, an Enterobacter cloacae strain isolated from soil derived from a municipal and electronic waste dumping site was engineered to serve as a bioluminescent bioreporter for mercury toxicity by linking its merR-like gene and promoter sequence to a reorganized luxABCDE gene cassette from Photorhabdus luminescens. This bioreporter, designated as E. cloacae DWH4lux , detected mercury (HgCl2 ) at a minimum concentration of 0·2µgl-1 with a linear response profile being maintained between a range of 0·4-1600µgl-1 (R2 =0·9604) with a peak bioluminescent response occurring within 1h after exposure. No significant synergistic or antagonistic influences were observed on the bioluminescent response by other contaminating metal elements. Enterobacter cloacae DWH4lux was also demonstrated to detect mercury effectively in artificially contaminated water sample with linear correlation (R2 =0·9623). The results indicated that E. cloacae DWH4lux could detect mercury in quantities below the US Environmental Protection Agency's permitted limit values (2µgl-1 ). Hence, it is concluded that E. cloacae DWH4lux has the potential to serve as an effective whole-cell bioreporter for the environmental monitoring of mercury contamination. This study provides new insight into the recruitment of mercury-tolerant bacterial hosts derived from environmental samples over the conventional lab-based E. coli host for the construction of mercury bioreporters. With improved response time and selectivity, the environmentally sourced bacteria can serve as an alternative host choice to improve biosensing technology in the near future.