Landfill Leachate Treatment Plant Research Articles

A study on the nitrogen removal efficacy of bacterium Acinetobacter tandoii MZ-5 from a contaminated river of Shenzhen, Guangdong Province, China

Heterotrophic nitrification–aerobic denitrification (HN-AD) has advantages over the traditional nitrogen removal process when removing multiple types of nitrogen in wastewater treatment. Acinetobacter tandoii MZ-5, which is capable of HN-AD, was isolated from the sediment of a polluted river for the first time. It used NH4+-N, NO2–-N and NO3–-N as sole nitrogen sources with maximum removal rates of 2.28, 1.18 and 1.04 mg L−1h−1, respectively. Simultaneous nitrification and denitrification were observed when using mixed N sources and NH4+-N was preferentially utilized. High nitrogen removal efficiencies (>90%) were achieved under the following conditions: C/N ratio 11–18, pH 6–8, 25–30 °C and dissolved oxygen 7.35–7.66 mg L−1. Strain MZ-5 was effective at treating wastewater from landfill leachate treatment plants, with NH4+-N, NO3–-N and total nitrogen (TN) removal efficiencies of 99.28%, 44.85% and 45.31%, respectively. Thus, strain MZ-5 may be a good candidate for wastewater treatment.

Fate and removal of aromatic organic matter upon a combined leachate treatment process

Mature leachates contain extremely recalcitrant aromatic organic matter, and require appropriate treatment before discharge. The combined process for treating mature landfill leachate is a common and proper due to its inexpensiveness and high performance. Identification of refractory components and insights into the physicochemical properties transformations of the organics are essential for the development of efficient treatment process. Optical, three-dimensional chromatography and electrochemical techniques were applied to characterize aromatic organic matter in leachate from a pilot landfill leachate treatment plant. Results showed that the combination of biological contact oxidation, iron-carbon micro-electrolysis, Fenton, coagulation and integrated activated sludge system could efficiently remove 95.5% COD and 88.3% DOC in leachate organic matter, together with a simultaneous reduction in its molecular weight (MW), aromaticity, polarity, and humification degree. The low MW proteinaceous, carboxylic acid and amine-containing fractions were preferentially removed in biological contact oxidation process, whereas the hydrophilic humic substances with the MW > 4.0 kDa were the main species against biological treatment. Conversely, the advanced oxidation processes (AOPs) could efficiently destroy high MW, aromatic rings and conjugated moieties fractions, resulting in an increase in the leachate biodegradability. The oxygen-containing moieties generated in the AOPs were bridged by the flocculants to promote precipitate during the coagulation process, and the polymerized metastable organic fractions formed during the process were partly biodegraded in the integrated activated sludge system. This study highlights the potential of combined optical-electrochemical measurements to monitor the intrinsic reactivity of aromatic organic matter and guide the practical leachate treatment.

Taxonomic and functional variations in the microbial community during the upgrade process of a full-scale landfill leachate treatment plant — from conventional to partial nitrification-denitrification

Because of the low access to biodegradable organic substances used for denitrification, the partial nitrification-denitrification process has been considered as a low-cost, sustainable alternative for landfill leachate treatment. In this study, the process upgrade from conventional to partial nitrification-denitrification was comprehensively investigated in a full-scale landfill leachate treatment plant (LLTP). The partial nitrification-denitrification system was successfully achieved through the optimizing dissolved oxygen and the external carbon source, with effluent nitrogen concentrations lower than 150 mg/L. Moreover, the upgrading process facilitated the enrichment of Nitrosomonas (abundance increased from 0.4% to 3.3%), which was also evidenced by increased abundance of amoA/B/C genes carried by Nitrosomonas. Although Nitrospira (accounting for 0.1%–0.6%) was found to stably exist in the reactor tank, considerable nitrite accumulation occurred in the reactor (reaching 98.8 mg/L), indicating high-efficiency of the partial nitrification process. Moreover, the abundance of Thauera, the dominant denitrifying bacteria responsible for nitrite reduction, gradually increased from 0.60% to 5.52% during the upgrade process. This process caused great changes in the microbial community, inducing continuous succession of heterotrophic bacteria accompanied by enhanced metabolic potentials toward organic substances. The results obtained in this study advanced our understanding of the operation of a partial nitrification-denitrification system and provided a technical case for the upgrade of currently existing full-scale LLTPs.

Antibiotic resistome in a landfill leachate treatment plant and effluent-receiving river.

Landfills leachate contained diverse antibiotic resistance genes (ARGs). Treated landfill leachate effluent could enter into the downstream environments, leading to the dissemination of ARGs, which might pose a health risk to public. Here, we used high-throughput qPCR to characterize the resistome and 16S rRNA-based Illumina sequencing to analyze the bacterial community in a leachate treatment plant and the river near the landfill. A total of 91 ARGs and 5 mobile genetic elements were detected. Leachate treatment process significantly changed the profiles of resistome and bacterial community structures. Similar bacterial community structure and ARG profiles were detected between effluent and downstream river, which were both dominated by multidrug and beta-lactams resistance genes and harbored higher ARG relative abundance than that in upstream river. In particular, seven ARGs were detected both in effluent and downstream river samples but not detected in upstream river, including genes encoding resistance to vancomycin (vanXD and vanSB) and carbapenem (cphA and blaGES), which implied the effects of the effluent on its receiving river. This study highlights the risk of discharge of processed landfill leachate in dissemination of antibiotic resistance determinants to the environments, and suggests an urgent need for surveillance of ARGs and development of techniques to mitigate the risk.

ISOLATION AND IDENTIFICATION OF MICROALGAE FROM HIGH NITRATE LANDFILL LEACHATE

This study aims to isolate and identify microalgae capable of growing in high nitrate (N-NO3-) landfill leachate. Source of isolation was collected from a landfill leachate treatment plant and identified according to morphological characteristics and analysis of partial 18S and 28S rRNA genes. The isolates, identified as Chlorella vulgaris UPSI-JRM01 and Tetradesmus obliquus UPSI-JRM02 were capable of growing at high N-NO3- concentration of nitrified landfill leachate, which is up to 1500 mg/L. The biomass productivities of Chlorella vulgaris and Tetradesmus obliquus were 36.28 mg/L/day and 40.49 mg/L/day, with 44% and 37% N-NO3- removal, respectively. The biomass of Chlorella vulgaris and Tetradesmus obliquus consisted of 17.72% and 16.32% lipid and, 21.93% and 25.43% carbohydrate, respectively. The protein contents (>50%) were higher than lipid and carbohydrate contents for both microalgal species. The newly isolated microalgae species will be useful for future applications of high NO3- wastewater treatment and microalgae biomass production.

Temporal and spatial variation of greenhouse gas emissions from a limited-controlled landfill site

Landfilling biodegradable waste is an important source of global greenhouse gas (GHG) emissions. Among the several types of landfill, limited-controlled landfill is a common method used to dispose of domestic solid waste, especially in developing countries. However, information about GHG emissions from limited-controlled landfill sites has rarely been reported. In this study, the GHG emissions from a typical limited-controlled landfill site were investigated under a regular period for one year. The number and positions of static chambers were arranged according to the guidance on Monitoring Landfill Gas Surface Emissions by the UK Environment Agency to obtain representative data from the heterogeneous surface of the landfill. Inverse distance weighting (IDW) was applied to evaluate and visualise the GHG emissions from the whole landfill surface based on the measurements of distributed static chambers. As an important GHG source of the landfill site, the emissions from the landfill leachate treatment plant were also measured. The results revealed that CH4 and N2O emission fluxes from the landfill area were 1324.73 ± 2005.17 mg C m−2 d−1 and 2.16 ± 2.33 mg N m−2 d−1, respectively, and the fluxes from the leachate treatment plants were 23.92 ± 29.20 mg C m−2 d−1 and 16.40 ± 16.89 mg N m−2 d−1, respectively. CH4 and N2O releases preferred to present spatial heterogeneity, while temporal heterogeneity was expected to exist in CH4 and CO2 emissions. The annual GHG emissions from the limited-controlled landfill was calculated to be 1.078 Gg CO2-eq yr−1, which was the least among all types of landfill sites. In addition, the GHG emission factor was 0.042 t CO2-eq t−1 waste yr−1 which could not be ignored compared to the sanitary landfills. Therefore, it is advisable to give more attention and determine a potential solution for reducing GHG emissions from limited-controlled landfill sites.

Landfill leachate treatment in Lithuania

Around 6 million tons of non- hazardous waste and some 1 30-1 70 000 tons of hazardous waste is generated in Lithuania every year. Most of non-hazardous wastes are organic (2. 1 millions tons) or domestic (1.7 million ton). Since no general waste incineration is used in Lithuania, the overall used method of waste disposal is landfilling. Most of the landfills are not designed or located properly. They pose a threat for both surface and groundwater in Lithuania. The Lithuanian government has made environmental protection a priority concern in recent years. Bilateral and multilateral donors have made funding available for environmental projects. Until 1998 no landfill in Lithuania had a landfill leachate treatment plant. Leachate was kept in the special storage places in the landfill, or collected and recirculated. In Vilnius, the capital of Lithuania, part of the landfill leachate is taken to the city's waste water treatment plant and part of it is recirculated. Competition for the landfill leachate plant was announced and hopefully in the near future Vilnius will have a real project for the landfill leachate treatment. Recirculation was carried out in Kaunas Lapes landfill too till the leachate treatment plant was built. Leachate is collected and kept in the ditches in the other three biggest cities of Lithuania - Klaipeda, Siauliai and Panevezys. Klaipeda, as all other cities, is looking for a cost effective solution for the leachate treatment and Panevezys is thinking to clean the leachate in the city's waste water treatment plant. Biological leachate treatment is the idea of Siauliai municipality.

Combination of self-organizing map and parallel factor analysis to characterize the evolution of fluorescent dissolved organic matter in a full-scale landfill leachate treatment plant

The dissolved organic matter (DOM) characterization in a full-scale landfill leachate treatment plant is of great importance for the design and operation of treatment processes. In this study, the long-term removal behaviors of DOM during landfill leachate treatment were explored using excitation emission matrix fluorescence spectroscopy (EEMs) coupled with parallel factor analysis (PARAFAC) and self-organizing map (SOM). Results indicated that the application of combining PARAFAC and SOM on EEMs analysis effectively characterized long-term removal behaviors of DOM during leachate treatment. The DOM in raw leachate was dominated by humic substances, while its composition exhibited significant seasonal differences. A large proportion of protein-like fluorescent dissolved organic matter (FDOM) and bulk DOM were removed within membrane bioreactor (MBR) system. Meanwhile the humic-like FDOM removal capacity in nanofiltration (NF) process was well comparable with those in the MBR system owing to the bio-recalcitrant nature of humic substances. The protein-like FDOM and bulk DOM were removed synchronously in both the process of MBR and NF. Moreover, samples distribution exhibited obvious differences among NF concentrate samples. In general, the performance of MBR-NF treatment for landfill leachate displayed reasonable stability in DOM removal irrespective of seasonal variations. This study enhanced our understanding of EEMs application in characterizing leachate-derived DOM composition and has potential implications for the associated monitoring investigations in engineered systems.

Electrooxidation as post treatment of ultrafiltration effluent in a landfill leachate MBR treatment plant: Effects of BDD, Pt and DSA anode types

In this study, ultrafiltration (UF) effluent from a landfill leachate treatment plant (equipped with anoxic-aerobic oxidation and UF) was treated by Electrooxidation (EO) process in a batch reactor using different dimensionally stable electrodes (DSA anodes: Ti/PtO2-IrO2, Ti/RuO2-TiO2, Ti/RuO2-IrO2, and Ti/IrO2-Ta2O5), boron doped diamond (BDD) and Pt as anode and stainless-steel electrode as cathode. The untreated UF effluent had COD and TOC concentrations of 888 mg/L and 398.6 mg/L, respectively. Overall, BDD anode performed better than the other DSA anodes under the tested conditions with removal efficiencies of 64.9–86.8% and 68.2–92.0% for TOC and COD, respectively. The calculated energy consumptions at maximum removal efficiencies were 111.2 kWh per m3 (136.01 kWh/kg COD and 321.27 kWh/kg TOC) at 360 A/m2 and 4 h of treatment time for BDD anode. However, TOC and COD removal efficiencies of 31.3–86.8% and 36.5–92.0%, respectively, were obtained for the other DSA anodes at current densities between 60 and 360 A/m2 and 4 h of treatment time. Energy consumptions and anode efficiency for DSA anodes ranged from 7.3–111.2 kWh/m3 (15.67–194.87 kWh/kg COD) and 4.40–34.24 g COD/Ah m2 (or 1.77–14.62 g TOC/Ah m2). The general COD and TOC removal mechanism well fitted the pseudo first-order kinetic model with R2 of >0.94 particularly for BDD electrode under all applied current densities. The chloride content in the leachate promoted indirect oxidation leading to higher COD and TOC removal efficiencies. Moreover, high performance size exclusion chromatography (HPSEC) was used to evaluate the variation of fractions in wastewater during EO.

RDNA- and rRNA-derived communities present divergent assemblage patterns and functional traits throughout full-scale landfill leachate treatment process trains

Understanding the influences of microbial interactions and niche heterogeneities on microbial communities and functional traits is critical for determining its engineering and ecological significance. However, little is known about microbial community assemblage and functional gene expression throughout full-scale landfill leachate treatment plants. Here, we applied a combination of 16S rRNA and rDNA amplicon sequencing, shotgun metagenomic, and qPCR approaches to unveil the ecological associations between distinct communities, functional gene expression and nitrogen cycling processes. By comparing the rDNA and rRNA-derived communities, the rRNA/rDNA ratios suggested that 57.2% of rare taxa were active, and their abundance decreased as increasing of potential activities. In particular, rDNA- and rRNA-based communities exhibited divergent assemblage patterns, and stronger intra-associations among core taxa in the rRNA-based communities than in rDNA-based communities. Furthermore, results regarding both bacterial assemblage and functional traits indicated that the habitat filtering and niche differentiation (treatment units) exerted selection on microbial communities based on functional traits, particular for key ecological functions related to nitrogen cycling. Collectively, our findings provide insights into structure-function associations at the local level and shed light on ecological rules guiding rDNA- and rRNA-based community assembly in landfill leachate treatment systems.

Environmental assessment of a landfill leachate treatment plant: Impacts and research for more sustainable chemical alternatives

Abstract The aim of this study is to evaluate, from an environmental point of view, the performance of various technologies applied to the treatment of municipal landfill leachate. The study has been led in an Italian wastewater treatment plant and it applies the principles of the Life Cycle Assessment (LCA) technique, using ReCiPe as the assessment method. This study shows how the operating stage of a wastewater treatment plant, that applies chemical and physical treatments, can affect the following four environmental impact categories: “Freshwater Eutrophication”, “Freshwater Ecotoxicity”, “Marine Ecotoxicity” and “Human Toxicity”. Within this operating stage, the study shows the relevant environmental impacts generated by the use of polyaluminum chloride (PAC) as a coagulant chemical agent and sodium hydroxide (caustic soda) as a pH control chemical agent. In order to investigate these results, and to discover more eco-friendly alternatives, two LCA comparisons have been carried out, comparing respectively the above two agents to analogous and common substitutes: ferric chloride as a coagulant agent and calcium hydroxide (lime) as a pH control agent. These comparisons demonstrate the higher environmental impacts of the use of ferric chloride over PAC and of sodium hydroxide over calcium hydroxide. Ferric chloride has shown to have more than double the environmental impact of PAC in 9 environmental categories out of the 10 considered, while calcium hydroxide has been able to cut down the negative environmental impacts of the sodium hydroxide of more than 65% in all the environmental categories. Considering the highly positive environmental results achieved from our study, whenever possible, a substitution of calcium hydroxide to sodium hydroxide and of PAC to ferric chloride is strongly recommended.

Performance evaluation of a biological landfill leachate treatment plant and effluent treatment by electrocoagulation

A major problem in municipal waste landfills is generation of leachate, a dark black colored liquid with high concentrations of pollutants. The objectives of this study were to evaluate the efficiency of available leachate treatment methods at a biological treatment plant and the electrocoagulation (EC) process using aluminum and iron electrodes for treatment of effluent from the biological treatment plant. In this experimental study, leachate from the AqQala landfill in Gorgan was examined. Equipment for electrochemical unit included a power supply as well as iron and aluminum electrodes. The EC process was operated under different reaction times (20, 40, 60 min), pH values (3, 7, 9) and current densities (1.66, 3.33, 5A/m2 ). The results showed that the effluent from the biological treatment plant has high concentrations of organic matter similar to wastewater, and should therefore be treated before discharge to the environment. According to the results, increasing the reaction time or the current density in the EC process increases the removal efficiency. The EC process is suggested as an alternative treatment process with high efficiency for the removal of organic matter, nitrate, phosphorous and turbidity in sewage treatment, which could prevent water and soil pollution.

A sequential treatment of intermediate tropical landfill leachate using a sequencing batch reactor (SBR) and coagulation

The increase in landfill leachate generation is due to the increase of municipal solid waste (MSW) as global development continues. Landfill leachate has constantly been the most challenging issue in MSW management as it contains high amount of organic and inorganic compounds that might cause pollution to water resources. Biologically treated landfill leachate often fails to fulfill the regulatory discharge standards. Thus, to prevent environmental pollution, many landfill leachate treatment plants involve multiple stages treatment process. The Papan Landfill in Perak, Malaysia currently has no proper leachate treatment system. In the current study, sequential treatment via sequencing batch reactor (SBR) followed by coagulation was used to treat chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N), total suspended solids (TSS), and colour from raw landfill leachate. SBR optimum aeration rate, L/min, optimal pH and dosage (g/L) of Alum for coagulation as a post-treatment were determined. The two-step sequential treatment by SBR followed by coagulation (Alum) achieved a removal efficiency of 84.89%, 94.25%, 91.82% and 85.81% for COD, NH3-N, TSS and colour, respectively. Moreover, the two-stage treatment process achieved 95.0% 95.0%, 95.3%, 100.0%, 87.2%, 62.9%, 50.0%, 41.3%, 41.2, 34.8, and 22.9 removals of Cadmium, Lead, Copper, Selenium, Barium, Iron, Silver, Nickel, Zinc, Arsenic, and Manganese, respectively.

Enhancing filterability of activated sludge from landfill leachate treatment plant by applying electrical field ineffective on bacterial life.

The aim of this study is to investigate filterability enhancement of activated sludge supplied form a full-scale leachate treatment plant by applying DC electric field while keeping the biological operational conditions in desirable range. The activated sludge samples were received from the nitrification tank in the leachate treatment plant of Istanbul's Odayeri Sanitary Landfill Site. Experimental sets were conducted as laboratory-scale batch studies and were duplicated for 1A, 2A, 3A, 4A, and 5A of electrical currents and 2, 5, 10, 15, and 30min of exposure times under continuous aeration. Physicochemical parameters such as temperature, pH, and oxidation reduction potential in the mixture right after each experimental set and biochemical parameters such as chemical oxygen demand, total phosphorus, and ammonia nitrogen in supernatant were analyzed to define the sets that remain in the range of ideal biological operational conditions. Later on, sludge filterability properties such as capillary suction time, specific resistance to filtration, zeta potential, and particle size were measured for remaining harmless sets. Additionally, cost analyses were conducted in respect to energy and electrode consumptions. Application of 2A DC electric field and 15-min exposure time was found to be the most favorable conditions to enhance filterability of the landfill leachate-activated sludge.

Identification and Influence of Quorum Sensing on Anaerobic Ammonium Oxidation Process

Anaerobic ammonium oxidation (ANAMMOX), an innovative nitrogen removal technology, has good prospects for applications. However, ANAMMOX bacteria grow slowly and are hardly accumulated in bioreactors. In this study, a UASB reactor inoculated with sludge from landfill leachate treatment plant was used for the start-up of ANAMMOX process. Besides, exogenous quorum sensing signals (DSF and AHL) were added to improve the adhesion of ANAMMOX sludge. The results showed that the UASB successfully started the ANAMMOX process within 150 days of operation. The total nitrogen removal rate reached 80% and the proportion of ANAMMOX bacteria rose to 20%. There was a low concentration of AHLs signal molecules in the ANAMMOX sludge. If the β-position substituent group of AHL added was a carbonyl group (including 3-oxo-C6-HSL, 3-oxo-C8-HSL, 3-oxo-C10-HSL and 3-oxo-C12-HSL), the adhesion growth ability of the ANAMMOX sludge could be improved. In the case of dosing with AHL molecules without β-position substituent groups, only C6-HSL and C12-HSL could promote the adhesion of ANAMMOX sludge. The additions of C8-HSL, C10-HSL and DSF all had negative effects on the adhesion of ANAMMOX sludge.

Occurrence of antibiotic resistance genes in landfill leachate treatment plant and its effluent-receiving soil and surface water

The antibiotic resistance genes (ARGs) from urban waste may spread to the environment with the discharge of leachate. Fifteen types of ARGs, including tetracycline, sulfonamides, AmpC β-lactamase and the class 1 integron gene were detected in the samples from the largest leachate treatment plant (LTP) in Guangzhou and its effluent receiving bodies (soil and surface water). The results showed that ARGs in leachates were in high levels and varied with seasons. The abundance of ARGs in the influent from high to low was in the turn of summer, winter, spring. About 2 to 4 orders of magnitude of ARGs were eliminated by the whole leachate treatment process. The predominant ARGs in the receiving soil were intI1, tetB, sul2, tetA and tetX, while those in the receiving surface water were sul2, intI1 and sul1, and the concentrations of ARGs in the receiving bodies were higher than those in the other natural bodies by 1 to 2 orders of magnitude. In addition, the results of bivariate correlation analysis showed that the abundances of ARGs (tetC, tetW, sul1, sul2, intI1 and FOX) were in significant correlation with the concentrations of heavy metals (Cu, Zn, Ni and Cr) (p < 0.05). LTPs are more likely to be sources of ARGs than wastewater treatment plant (WWTP) and need to be focused on.

Occurrence and treatment efficiency of pharmaceuticals in landfill leachates

Landfill leachates might contain pharmaceuticals due to the expired or unwanted drugs were disposed of at landfills. These pharmaceuticals might pose a threat to soil and groundwater. Therefore, this study investigated the distributions of pharmaceutical residues and toxicities among four typical municipal landfill leachates. Twenty six pharmaceuticals were investigated in this study and fifteen of them were found in all samples from four leachates. In addition, ampicillin and methylenedioxymethamphetamine (MDMA) were detected in urban landfills (A1 and A2) but were not in rural and suburb landfills (B and C). On the other hand, some compounds were much more abundant in suburb/rural landfill leachates than those in urban landfills including diclofenac, gemfibrozil and amphetamine. Landfill leachate treatment plants could not remove most of the pharmaceuticals effectively. Landfill leachates without proper treatments would have significant adverse health impacts on human and aquatic life.

Removal of refractory organics in nanofiltration concentrates of municipal solid waste leachate treatment plants by combined Fenton oxidative-coagulation with photo--Fenton processes.

Removal of the refractory organic matters in leachate brines generated from nanofiltration unit in two full-scale municipal solid waste landfill leachate treatment plants was investigated by Fenton oxidative-coagulation and ultraviolet photo - Fenton processes in this study. Fenton oxidative-coagulation was performed under the condition of an initial pH of 5.0 and low H2O2/Fe(2+) ratios. After precipitate separation, the remaining organic constituents were further oxidized by photo - Fenton process. For both leachate brines with varying pollution strength, more than 90% COD and TOC reductions were achieved at H2O2/Fe(2+) dosages of 35 mM/8 mM and 90 mM/10 mM, respectively. The effluent COD ranged 120-160 mg/L under the optimal operating conditions, and the biodegradability was increased significantly. Fenton oxidative-coagulation was demonstrated to contribute nearly 70% overall removal of organic matters. In the combined processes, the efficiency of hydrogen peroxide varied from 216 to 228%, which may significantly reduce the operating cost of conventional Fenton method. Six phthalic acid esters and thirteen polycyclic aromatic hydrocarbons were found in leachate brines, and, on the average, around 80% phthalic acid esters and 90% polycyclic aromatic hydrocarbons were removed by the combined treatments.

Greenhouse gas emissions from landfill leachate treatment plants: A comparison of young and aged landfill

With limited assessment, leachate treatment of a specified landfill is considered to be a significant source of greenhouse gas (GHG) emissions. In our study, the cumulative GHG emitted from the storage ponds and process configurations that manage fresh or aged landfill leachate were investigated. Our results showed that strong CH4 emissions were observed from the fresh leachate storage pond, with the fluxes values (2219–26,489mgCm−2h−1) extremely higher than those of N2O (0.028–0.41mgNm−2h−1). In contrast, the emission values for both CH4 and N2O were low for the aged leachate tank. N2O emissions became dominant once the leachate entered the treatment plants of both systems, accounting for 8–12% of the removal of N-species gases. Per capita, the N2O emission based on both leachate treatment systems was estimated to be 7.99gN2O–Ncapita−1yr−1. An increase of 80% in N2O emissions was observed when the bioreactor pH decreased by approximately 1 pH unit. The vast majority of carbon was removed in the form of CO2, with a small portion as CH4 (<0.3%) during both treatment processes. The cumulative GHG emissions for fresh leachate storage ponds, fresh leachate treatment system and aged leachate treatment system were 19.10, 10.62 and 3.63GgCO2eqyr−1, respectively, for a total that could be transformed to 9.09kgCO2eqcapita−1yr−1.

Susceptibility of Some Selected Nitte Municipal Wastewater Sources to Trace Metals Pollution

The negative impacts of pollution due to trace metals in wastewater on aquatic ecosystem and related organisms in water bodies are on the increase. This paper deals with the investigation on the pollution indices of trace metals in selected wastewater samples of Nitte Town, Udupi District, Karnataka State, India. Twelve wastewater samples were obtained from Students Hostels, Auto-Service Workshop Station, Foundry, Laundry, Landfill Leachate and Wastewater Treatment Plant Inlet. The measured heavy metals in the samples include: Copper (Cu), Lead (Pb), Magnesium (Mg), Chromium (Cr), Nickel (Ni), Zinc (Zn), Manganese (Mn) and Cadmium (Cd), using the air-acetylene-operated Flame Atomic Absorption Spectrometer (FAAS), Avanta GM model. The results were all compared with the EPA Effluent Standards. Findings revealed that all samples recorded dwindling levels of trace metals pollution when compared with the Standards. The heaviest concentration occurred in Cd with as high as 1856.4 ppm as found in the Stale Landfill Leachate sample, while the least contaminating metal in the samples is Manganese which was detected in only Aerated Wastewater Treatment Plant sample (2.3 ppm). This study is therefore recommending Electro-coagulation treatment method for trace metals with high concentration levels like Cd, Pb, Mg and Cu, while those with lesser concentration such as Mn, Cr, Ni and Zn in the samples are suggested to be treated with chemical precipitation method.