Treatment Efficiency Of Landfill Leachate Research Articles

Precise preparation of CoOx@KSB catalysts by atomic layer deposition for peroxymonosulfate activation and landfill leachate treatment

The construction of desired active sites is critical for enhanced activity in heterogeneous peroxymonosulfate (PMS) systems. In view of the shortcomings of the current construction methods, such as low precision and harsh conditions, CoOx@KSB catalysts were precisely prepared at the atomic level using atomic layer deposition in this study. Using alkali-modified sludge biochar (KSB) as a feedstock, two different deposition processes were proposed to investigate the preparation pattern on the treatment efficiency of landfill leachate. Results showed that the small-cycle layer-by-layer deposition (B process) not only preserved the original N sites of the catalyst after 150 depositions, but also obtained satisfactory Co2+. Under the optimal experimental conditions, KSB-B150 degraded more than 90% of SMX within 120 ​min. After 8 ​h of continuous operation in the packed column reactor, the COD concentration of the effluent landfill leachate was still below 100 ​mg/L, and the biotoxicity of the effluent was reduced to 0.41 times of the original. The Co2+, OV and graphite N sites could generate SO4•− and •OH, which played dominant roles in SMX degradation. This study provides a new strategy for constructing active sites in heterogeneous PMS system. It is beneficial to promote the application of heterogeneous advanced oxidation technology in landfill leachate treatment.

Application of Machine Learning (ML) and Artificial Intelligence (AI)-Based Tools for Modelling and Enhancing Sustainable Optimization of the Classical/Photo-Fenton Processes for the Landfill Leachate Treatment

This study presents a machine learning (ML)/artificial intelligence (AI)-based perspective to reliably predict and enhance the treatment efficiency of landfill leachate by classical-Fenton (c-Fenton) and photo-Fenton (p-Fenton) processes. This experiment also sought to lower treatment costs by evaluating the impact of using different numbers of UV-c (254 nm) lamps during p-Fenton processes, as well as to develop a sustainable process design for landfill leachate. In the modeling stage, the radial basis function neural network (RBFN), the feed forward neural network (FFNN), and the support vector regression (SVR) were used and the results were evaluated in a broad scanning. Our experimental results, optimized with the help of genetic algorithm (GA), showed an increasing trend in treatment efficiency and a decreasing trend in chemical usage amounts for p-Fenton oxidation. The results indicate that both treatment techniques performed (classical and p-Fenton) within 1 h contact time showed a very high pollutant removal with a reduction in COD of approximately 60% and 80%, respectively, during the first 30 min of processing. Additionally, it was noted that the COD elimination for the c-Fenton and the p-Fenton was significantly finished in first 15 min, 52% and 73%, respectively. According to the results of the optimization model, there is an increase from 62 to 82 percent under eight UV lamps compared to seven UV lamps when considering the impact of the number of UV lamps on the treatment efficiency in p-Fenton. It has been noted that when the results are taken as a whole, the better modeling abilities of ML-based models, particularly the RBFN and the FFNN, come to the fore. From a different angle, the FFNN and the RBFNN have both shown percentile errors that are extremely close to zero when MAPE values, a percentile error measure independent of the unit of the data set, are evaluated alone. Except for two tests whose desirability levels are still around 99.99%, all experiments attained outstanding desirability levels of 100.00%. This serves as more evidence for the higher modeling performance of these ML-based approaches.

Efficiency assessment of municipal landfill leachate treatment during advanced oxidation process (AOP) with biochar adsorption (BC)

Leachate generated in landfills are characterized by high toxicity related to, high concentrations of organic and non-organic pollutants, therefore, it is advisable to use highly effective methods of their purification to prevent environmental contamination. The aim of this study was to determine the treatment efficiency of landfill leachate during the application of integrated processes: advanced oxidation (AOP) and biochar adsorption (BC). In the case of the AOP, the chemical process was the Fenton reaction in which the source of hydroxyl radicals was H2O2 (system I) and SPC - sodium percarbonate (system II). Leachate was derived from the regional municipal waste landfill in Silesian Province (Poland) which was characterized by the pH of 8.40, COD value was 3155 mg L−1 and BOD was under 165 mg L−1. The BOD/COD ratio was at a low level (0.053) that indicated low biodegradability. The applied systems allowed of the COD reduction index to the level of 549 mg L−1 (H2O2+BC) and 944 mg L−1 (SPC+BC) where the limit threshold is 125 mg L−1. In the same case of the TOC index, these values were respectively 119 and 186 mg L−1, where the limit value is 30 mg L−1.This study has been aimed to estimate the toxicity of leachate treatment in integrated systems: AOP processes + biochar adsorption. Toxicity of treated and untreated leachate has been analysed by Sinapis alba and Lepidium sativum plants-based tests. It was found that while conducting the Fenton process as system I (H2O2) at all reagent doses, the removal efficiency of COD and TOC was 17% and 12% higher, respectively, compared to system II. The most advantageous dose of regents was 2.5:1 and biochar - 2 g L−1. It was observed that in the SPC+BC system the roots of L. sativum and S. alba were on average 34% and 28% longer compared to the H2O2+BC system. Higher germination index (GI) of both tested plants, indicating lower wastewater toxicity, was recorded for the SPC+BC system.

Photocatalytic efficiency of molybdenum-doped zinc oxide nanoparticles in treating landfill leachate

Among various techniques available for leachate treatment, nano-photocatalytic-based techniques have been considered as efficient. The photocatalytic leachate treatment using nanoparticles of zinc oxide doped with molybdenum oxide was performed in the presence of sunlight at a laboratory scale. The molybdenum oxide doped ZnO nanoparticles were synthesized. The properties of nanoparticle were analyzed by using FTIR, SEM, and XRD. Then the parameters such as pH (3, 5, 7, 9, & 11), concentration of nanoparticles (0.5, 1, 2 and 3 g/l), concentration of leachate with dilution (1:10, 1:25, 1:50 and 1:100), and contact time (15, 30, 45, 60, 90, & 120 min) were measured to determine the removal of COD and turbidity. The analysis indicated that nanoparticle size was appropriate and acceptable. Electron microscope images also showed that the nanoparticle shape was hexagonal. The optimum value of pH was 5. It was found that increasing the concentration of nanoparticles enhances the efficiency of the process, the concentration of nanoparticles from 0.5 to 2 g/l at 60 min of contact time, and the efficiency from 34.8 to 55.6%, and increasing in contact time decreases the COD and turbidity leachate. Enhancing the initial concentration of leachate reduces the treatment efficiency of landfill leachate.

Comparing young landfill leachate treatment efficiency and process stability using aerobic granular sludge and suspended growth activated sludge

The treatment of young landfill leachate was investigated using two 3L sequencing batch reactors (SBR) with different biomass: aerobic granular sludge (GSBR) and the suspended growth activated sludge (ASBR). According to the nature of aerobic granular sludge, high settling velocities were expected in the GSBR and it was confirmed with 60ml/gVSS of 5-min sludge volume index (SVI5). However, the activated sludge required 30min for the ASBR to achieve a SVI of 42ml/gVSS. Compared to the ASBR, the GSBR was also more efficient in nitrogen and carbon removal. During the steady period of the experiment, 99% of total ammonium nitrogen (TAN) was removed through nitritation and nitrification in the GSBR with an average influent TAN concentration of 498mg/L. With high influent TAN concentration, the GSBR could achieve a full nitrification efficiency of 56±12% without accumulating nitrite. On the contrary, complete nitrification was not achieved in the ASBR as it was exposed to high concentrations of free ammonia (FA) and free nitrous acid (FNA), 16 and 0.2mg/L respectively. Partial nitrification (nitritation) with the efficiency of 77±10% was observed in the ASBR. The GSBR also presented higher efficiency in denitrification compared to the ASBR. 23% denitrification was observed in the GSBR during the anaerobic phase. Moreover, higher chemical oxygen demand (COD) removal efficiency was observed in GSBR than ASBR. Phosphorus removal efficiency was almost identical in both reactors. Overall, compared with the activated sludge, the aerobic granular sludge showed the best nutrients removal performance and higher tolerance to toxic compounds in young landfill leachate.

Quantitative dynamics of ammonia-oxidizers during biological stabilization of municipal landfill leachate pretreated by Fenton’s reagent at neutral pH

The application of multi-stage systems including biological step, for the treatment of leachate from municipal landfills, is economically and technologically justified. When microbial activity is utilized as 2nd stage of treatment, the task of 1st stage is to increase the bioavailability of organic matter. In this work, the effect of advanced oxidation process by Fenton’s reagent for treatment efficiency of landfill leachate in the sequencing batch reactor was assessed. The quantitative dynamics of bacteria taking a part in ammonia removal process was evaluated by determination of number of DNA copies of 16S rRNA and amoA. Products of neutral pH chemical oxidation, had a definite positive impact on the quantity of β-proteobacteria 16S rRNA, whereas the same gene specified for Nitrospira sp. as well as amoA did not show a significant increase during the process of biological treatment, regardless of whether the reactor was fed with raw leachate or chemically pre-treated.

Application of multiple toxicity tests in monitoring of landfill leachate treatment efficiency.

Leachate from a closed landfill used for co-disposal of municipal and tannery waste was submitted to coagulation treatment, air stripping, adsorption on granular activated carbon, and Fenton oxidation with the aim to reduce toxicity of the leachate. Optimal operational conditions for each process were identified. The performance of the treatment was monitored by determination of organic matter (COD, DOC, BOD5), inorganic components (N-NH4(+), Cl(-), alkalinity, metals), organic compounds (BTEX, PAHs, PCBs, OCPs) while changes in toxicity were followed by multiple toxicity tests. Among the applied treatment techniques, adsorption on granular activated carbon was the most efficient method for removal of organic matter and metals while air stripping was the most efficient for removal of N-NH4(+) and reduction of toxicity. Lower reduction of organic matter content and toxicity was obtained during coagulation treatment. Fenton oxidation was effective for removal of COD; however, it negatively affected toxicity reduction. The combination of adsorption on granular activated carbon and air stripping led to an appreciable reduction of organic and inorganic pollutants and to leachate detoxification. Application of bioassays was helpful for assessing suitability of treatment methods and demonstrated that they are, together with physicochemical parameters, an indispensable part for monitoring of treatment efficiency.

Influence of recirculation in a lab-scale vertical flow constructed wetland on the treatment efficiency of landfill leachate

Landfill leachate taken from a landfill situated in the north-western region of Bulgaria has been treated in a laboratory scale vertical flow constructed wetland (VF-CW) at different flow rates (40, 60 and 82 ml min −1) and recirculation ratios (time of water running through wetland to time of quiet water – 1:1; 1:2; 1:3). Young Phragmites australis was planted on the top layer of the reactor. The low flow rate (40 ml min −1) and recirculation ratio of 1:3 allowed removal efficiencies of 96% for COD (in 8 days), 92% for BOD 5 (in 3 days), 100% for ammonia (in 5 days) and 100% for total phosphorus (in 2 days). At the highest flow rate studied (82 ml min −1) and shorter quiet period (recirculation ratio 1:1) the water needs longer period of treatment (2 days more according to COD). The results of this study indicate that both flow rate and recirculation ratio should be taken into account for proper design of VF-CW.

PERFORMANCE OF BIOLOGICAL TREATMENT OF HIGH‐LEVEL AMMONIA LANDFILL LEACHATE

The biological treatment efficiency of landfill leachate (LFL) from a Tunisian site collection was investigated in this study. The raw effluent was highly charged with organic matter (more than 25 g l−1 of chemical oxygen demand (COD)), ammonia (1.7 g l−1) and salts (20 g l−1). With the presence of heavy metals, phenols and hydrocarbons, LFL exhibited high toxicity to organisms since it totally inhibited the bioluminescence of Vibrio fischeri and the germination of Lepidium sativum seeds. The biological oxygen demand (BOD5)/COD ratio of 0.5 indicates that the effluent can be biologically treated. Sludge from a wastewater treatment plant was acclimatized to the effluent in continuous batches. During the acclimatization phase, the consortia demonstrated a good ability to remove organic matter and toxicity in spite of an increase of introduced load reaching 3.2 g of COD 1.d. Consequently, the biodegradation experiments were carried out in a stirred tank reactor (STR) at organic loading rate (OLR) ranging from 0.5 to 5.4 g l−1 per day. The hydraulic retention time was decreased from 50 days to 4.6 days. The process seemed to be efficient to eliminate organics and ammonia. The COD removal efficiency reached a maximum of 80% for a loading rate of 5.4 g l−1 per day. The values of N‐NH4 + became less than those recommended by standards requested for rejection in public canalizations. During the treatment process, the biomass was increased from 0.8 g l−1 at the start‐up of the process to 3 g l−1. On the other hand, results of toxicity examinations showed that the treatment was efficient to provide detoxification of the effluent indicating a good adaptability of the consortia in spite of the presence of problematic compounds. The increase of the loading rate up to 6 g l−1 was responsible for the perturbation of the system and caused an accumulation of residual COD and toxicity.

The application of hybrid system UASB reactor-RO in landfill leachate treatment

The aim of the paper was to study landfill leachate treatment efficiency during fermentation process in UASB reactor and post-treatment in RO process. In the first step of experiment, the granular sludge was acclimatized to treatment with high loaded synthetic wastewater. Next, the optimal concentration of raw leachate in synthetic wastewater was determined (5% v/v–40% v/v). At this stage, UASB reactor was operated at hydraulic retention time (HRT) of 7 days and organic loading rate (OLR) of 0.6 kg COD × m −3d −1. While the optimal concentration of raw leachate in synthetic wastewater (20% v/v) was determined, the HRT was shortened from 7 to 2 days with a increase of OLR from 0.6 to 2.0 kg COD × m −3d −1. The HRT (3 days) and OLR 1.3 kg COD × m −3d −1 were taken as the optimum fermentation process parameters. Under such designed conditions COD removal achieved value of 76%. The concentration of COD, BOD, ammonia nitrogen, chloride concentration in effluent was kept on the level of 960 mg O 2 × dm −3, 245 mg O 2 × dm −3, 196 mg NH 4 + × dm −3 and 2350 mg Cl − × dm −3 respectively. Due to poor quality of UASB effluent, wastewater was put into the post-treatment process. In RO process COD, BOD, chloride, ammonia nitrogen parameters were removed in 95.4%, 90.2%, 85.4% and 88.7% respectively.

Indirect oxidation effect in electrochemical oxidation treatment of landfill leachate

Treatment of a low BOD COD ratio landfill leachate was conducted by means of electrochemical oxidation process in this investigation. Under the operating conditions of 15 A/dm 2 current density and 7500 mg/l additional chloride concentration, 92% of the COD in the landfall leachate was removed after electrolysis for 240 min with a ternary SnPdRu oxide-coated titanium (SPR) anode. At the same time, about 2600 mg/l of ammonium in the landfill leachate was also removed completely. These results indicate that the electrochemical oxidation process is effective in removing pollutants from landfill leachate. In this investigation, the effects of operating parameters including anode material, current density, and chloride concentration on both chlorine/hypochlorite production and landfill leachate treatment efficiency were studied. It was found that the operating factors have the same effects on both chlorine/hypochlorite production efficiency and landfill leachate treatment efficiency. The results suggest that the removal of pollutants from landfill leachate by electrochemical oxidation process could be mainly attributed to the indirect oxidation effect of chlorine/hypochlorite produced during the electrolysis. Among the four anode materials investigated in this study, including graphite, PbO 2 Ti , DSA R, and SPR anodes, the SPR anode having a high electrocatalytic activity gave the best chlorine/hypochlorite production efficiency and landfill leachate treatment efficiency. In addition, the increases in both operating current density and chloride concentration also enhanced the indirect oxidation effect in the electrochemical oxidation treatment of landfill leachate.

Effect of Phosphorus Addition on Treatment Efficiency of a Lab Scale Anaerobic Filter, Treating Landfill Leachate

Abstract Sanitary landfill leachate has been a source of environmental concern due to its high organic strength and chemical diversity. A number of lab-scale and pilot scale studies have indicated that the anaerobic filter is highly competitive with other forms of biological treatment and has distinct economic advantages. While there have been a number of studies based on a general overall approach to leachate treatment by the anaerobic filter, limited information is available on the role played by essential nutrients like nitrogen and phosphorus in the biological treatment process. Laboratory studies were conducted at room temperature (22 °C) to study the effect of nutrient addition (specifically, phosphorus, the deficient constituent of leachate) on treatment efficiency of landfill leachate by the upflow anaerobic filter. Two anaerobic filters (0.975 metres x 0.15 metres diameter) were constructed using plexiglass pipes and packed with strips of corrugated fibre-glass sheets in four layers to form the filter bed. Leachate collected from a nearby landfill was applied at moderate organic loadings (1.8-4.0 kg COD/m3/day) to the two units maintaining a HRT of 0.987 days. Results indicate phosphorus addition may be made to organically diverse wastes such as landfill leachate with distinct advantages.