Concentrations Of Landfill Leachate Research Articles

Treatment of landfill leachate by black soldier fly (Hermetia illucens L.) larvae and the changes of intestinal microbial community

Black soldier fly larvae (BSFL) (Hermetia illucens) are commonly used to treat organic waste. This work aims to evaluate the transformation effect, heavy metal migration, and alterations in the gut microbiota of BSFL in addition to treating landfill leachate (LL) with BSFL. We found that BSFL may grow in various landfill leachate concentrations without obvious toxicity and growth inhibition. In addition, the results indicated a significant increase in the content of ammonia nitrogen and the activity of urease and β-glucosidase (β-GC) in LL, increased from 2570.17 mg/L to 5853.67 mg/L, 1859.17 mg/(g·d) to 517,177.98 mg/(g·d), 313.73 μg/(g·h) to 441.91 μg/(g·h) respectively. Conversely, the content of total nitrogen (TN) and total organic carbon (TOC) decreased in LL, decreasing by 31.24% and 29.45% respectively. Heavy metals are accumulated in the leachate by the BSFL to differing degrees, the descending sequence of accumulation is Cd > As > Cu > Cr. As dropped by 26.0%, Cd increased by 22.6%, Cu reduced by 5.23%, and Cr increased by 317.1% in the remaining matrix. The concentration of heavy metals satisfies the organic fertilizers' limit index (NY/T1978). The diversity of intestinal microorganisms in BSFL decreased, from 2819 OTUs to 2338 OTUs, with Providencia and Morganella emerging as the core flora. The gene abundance of nitrogen metabolism in the microbiota increased significantly. The TOC, β-GC, and Copper (Cu) content in BSFL correlated significantly with the gut microbiota. In Summary, this study revealed the treatment effect of BSFL on LL, the migration of heavy metals, and changes in the intestinal microorganisms of BSFL. The content of heavy metals in BSFL was found to be much lower than the upper limit of feed protein raw materials, demonstrating that BSFL is a sustainable method to treat LL.

Characterization of per- and polyfluoroalkyl substances (PFAS) and other constituents in MSW landfill leachate from Puerto Rico

Elevated per- and polyfluoroalkyl substance (PFAS) concentrations have been reported in municipal solid waste (MSW) landfill leachate with higher levels in wet and warmer subtropical climates. Information about landfill leachate characteristics is much more limited in tropical climates. In this study, 20 landfill leachate samples were collected from three MSW landfills on the tropical island of Puerto Rico and results were compared against landfills nationally and within Florida, USA. The samples collected in Puerto Rico underwent physical-chemical analysis, as well as a quantitative analysis of 92 PFAS. Samples described in this study include discrete leachate types, such as leachate, gas condensate, and leachate which has undergone on-site treatment (e.g., RO treatment, phytoremediation, lagoons). A total of 51 PFAS were detected above quantitation limits, including perfluorohexylphosphonic acid, a perfluoroalkyl acid (PFAA) which has not been reported previously in landfill leachate. ∑PFAS concentrations in this study (mean: 38,000 ng L−1), as well as concentrations of individual PFAS, are significantly higher than other reported MSW landfill leachate concentrations. The profiles of leachates collected from on-site treatment systems indicate possible transformation of precursor PFAS as a result of treatment processes – oxidizing conditions, for example, may facilitate aerobic transformation, increase the concentrations of PFAAs, and possibly increase the apparent ∑PFAS concentration. Extreme climate events, including rising temperatures and more frequent hurricanes, have placed additional strain on the solid waste management infrastructure on the island – adding complexity to an already challenging PFAS management issue. As concern grows over PFAS contamination in drinking water, these findings should inform solid waste and leachate management decisions in order to minimize PFAS emissions in island environments.

Electrochemical-coupled sulfur-driven autotrophic denitrification for nitrogen removal from raw landfill leachate: Evaluation of performance and mechanisms

The cost-effective and environment-friendly sulfur-driven autotrophic denitrification (SdAD) process has drawn significant attention for advanced nitrogen removal from low carbon-to-nitrogen (C/N) ratio wastewater in recent years. However, achieving efficient nitrogen removal and maintaining system stability of SdAD process in treating low C/N landfill leachate treatment have been a major challenge. In this study, a novel electrochemical-coupled sulfur-driven autotrophic denitrification (ESdAD) system was developed and compared with SdAD system through a long-term continuous study. Superior nitrogen removal performance (removal efficiency of 89.1 ± 2.5 %) was achieved in ESdAD system compared to SdAD process when treating raw landfill leachate (influent total nitrogen (TN) concentration of 241.7 ± 36.3 mg-N/L), and the effluent TN concentration of ESdAD bioreactor was as low as 24.8 ± 5.1 mg-N/L, which meets the discharge standard of China (< 40 mg N/L). Moreover, less sulfate production rate (1.3 ± 0.2 mg SO42−−S/mgNOx−−N vs 1.7 ± 0.2 mg SO42−−S/mgNOx−−N) and excellent pH modulation (pH of 6.9 ± 0.2 vs 5.8 ± 0.4) were also achieved in the ESdAD system compared to SdAD system. The improvement of ESdAD system performance was contributed to coexistence and interaction of heterotrophic bacteria (e.g., Rhodanobacter, Thermomonas, etc.), sulfur autotrophic bacteria (e.g., Thiobacillus, Sulfurimonas, Ignavibacterium etc.) and hydrogen autotrophic bacteria (e.g., Thauera, Comamonas, etc.) under current stimulation. In addition, microbial nitrogen metabolic activity, including functional enzyme (e.g., Nar and Nir) activities and electron transfer capacity of extracellular polymeric substances (EPS) and cytochrome c (Cyt-C), were also enhanced during current stimulation, which facilitated the nitrogen removal and maintained system stability. These findings suggested that ESdAD is an effective and eco-friendly process for advanced nitrogen removal for low C/N wastewater.

Achieving advanced nitrogen removal from mature landfill leachate in continuous flow system involving partial nitrification-anammox and denitrification

Considering the challenges associated with nitrogen removal from mature landfill leachate, a novel combined continuous-flow process integrating denitrification and partial nitrification-Anammox (PN/A) was developed using an internal circulation (IC) system and a biological aerated filter (BAF) biofilm reactor (IBBR). In this study, IBBR successfully operated for 343 days, and when influent NH4+-N concentration of mature landfill leachate reached 1258.1 mg/L, an impressive total nitrogen removal efficiency (TNRE) of 93.3 % was achieved, along with a nitrogen removal rate (NRR) of 1.13 kg N/(m3·d). The analysis of the microbial community revealed that Candidatus Kuenenia, the dominant genus responsible for anammox, accounted for 1.7 % (day 265). Additionally, Nitrosomonas, Thauera and Truepera were identified as key contributors to the efficient removal of nitrogen from mature landfill. As a novel nitrogen removal strategy, the practical application of the IBBR system offers novel perspectives on addressing mature landfill leachate.

The residual crude glycerol enhancement of the ammoniacal nitrogen bioremediation by microalgae and bacteria consortium with concomitant production of PHAS and pigments of industrial interest

The landfill leachate and industrial effluents (farm of swine, poultry, cattle, distilleries, etc.) present concentrations above 800 mg.L−1 of ammoniacal nitrogen. The absence of economically viable processes for its removal has led to the loss of the water body potability. An innovative bioprocess was developed for the bioremediation of NH3. The residual crude glycerol from biodiesel production was innovatively used in a mixed culture of heterotrophic bacteria and cyanobacteria to reduce the NH3 toxicity and enhance the consumption of the NH3. >600 mg.L−1 of NH3 (consumption of 100 mg.L−1.d−1) was consumed in just 8 days, with efficiency of 100 % approximately. Also, there was a promising production of compounds of industrial interest by these microorganisms: polyhydroxyalkanoates (PHAs) for biodegradable plastics by heterotrophic bacteria (132 ± 19 mg.g−1); pigments by A. platensis (phycocyanin: 84.2 ± 2.8 mg.g−1 and total carotenoid: 1.62 ± 0.18) and proteins (38 ± 2 %)., with a maximum biomass productivity of 0.435 ± 0.004 mg.L−1.d−1.

Efficient nitrogen removal from mature landfill leachate by single-stage partial-nitritation anammox using expanded granular sludge bed

The effective retention of anaerobic ammonia oxidizing (anammox) bacteria and its high sensitivity to toxic substances and oxygen posed a major challenge to the application of partial nitrification combined with anammox (PN/A) in mature landfill leachate treatment, although it is a promising and efficient nitrogen removal process. In this study, a single-stage PN/A process based on expanded granular sludge bed was proposed to treat the mature landfill leachate. During the last phase, when the NH+ 4-N concentration of mature landfill leachate in influent was 1150.0 mg/L, the nitrogen removal efficiency (NRE) was 83.64% with 1.07 kg N/(m3·d) nitrogen removal rate (NRR). The activity of anammox bacteria (AnAOB) and ammonia oxidizing bacteria (AOB) was 9.21 ± 0.22 mg N/(gVSS·h) and 14.34 ± 0.65 mg N/(gVSS·h), respectively. The bacteria produced a high amount of tightly bound extracellular polymeric substance (TB-EPS) i.e., 4071.79 mg/(g·VSS). This helped to create granular sludge and provided favorable spatial conditions for the distribution of functional bacteria that were adapted to different environments. Due to the efficient retention of functional bacteria by the granular sludge, the relative abundance of Ca.Brocadia and Ca.Kuneneia was 1.71% and 0.31%, respectively. Redundancy analysis (RDA) and microbial correlation network diagram showed that the relative abundance of Ca. Kuenenia, Nitrosomonas and Truepera had a stronger positive correlation with the increase of the proportion of mature landfill leachate added to the influent. Overall, the PN/A process based on granular sludge provides an effective method for autotrophic biological nitrogen removal from mature landfill leachate.

Potential toxicity of landfill leachate to zebrafish and mung beans.

Landfill leachate has become a major public health concern due to its adverse health effects. However, its toxicological effects have not been thoroughly determined because of its complex composition. To address this issue, two model organisms were used in this study, including mung beans and zebrafish. Bean seedlings were exposed to different concentrations of landfill leachate (1%, 5%, 10%, 15%, and 20%, v/v, leachate/deionized water) for 7days. Low concentrations (1%) of landfill leachate increased the growth of mung beans, whereas high concentrations (15% and 20%) of landfill leachate inhibited the growth and development of seedlings. Furthermore, landfill leachate reduced chlorophyll levels but increased malondialdehyde levels, leading to an increased rate of root-tip micronuclei. Zebrafish embryos were exposed to different concentrations of landfill leachate (0.5%, 1.0%, 1.2%, and 1.5%, v/v, leachate/E3 medium) for 120h. The results showed that landfill leachate significantly decreased lower levels of hatching rate and heart rate but increased the mortality and malformation rates of embryos. Moreover, 1.0% landfill leachate reduced the frequency of spontaneous movement and the light stimulation reaction of embryos. Embryos exposed to leachate showed less exploratory behavior and fewer mirror attacks in the black and white areas. Our results suggest that exposure to landfill leachate could cause developmental toxicity and genotoxicity in plants and fish. The findings can improve our understanding of the environmental toxicity of landfill leachate and provide additional evidence for its risk assessment and management.

Co-treatment of stabilized landfill leachate and municipal wastewater in a granular activated carbon-sequencing batch reactor (GAC-SBR)

A laboratory-scale granular activated carbon-sequencing batch reactor (GAC-SBR) was used to co-treat stabilized landfill leachate with municipal wastewater. GAC-SBR was studied for the different mixing ratios of leachate and municipal wastewater at different hydraulic retention time (HRT). GAC dose (5, 10, 15 and 20 g/L) was optimized for COD reduction with a contact time of 22 h. GAC-SBR treatment efficiency was assessed on mixed liquor suspended solids (MLSS), mixed liquor volatile suspended solids (MLVSS), turbidity, chemical oxygen demand (COD), ammonia, nitrate, and phosphate removal. Univariate ANOVA was applied to test the statistical significance of treatment at different leachate:wastewater ratios. Results showed that the increase in GAC concentration led to an increase in the removal of COD and ammonia from stabilized landfill leachate. Adsorption efficiency decreased or remained constant after 15 g/L GAC. GAC-SBR was efficient in removing COD (83%) and nutrients (80–90%) from stabilized landfill leachate at 10 d HRT. Univariate analysis of variance (ANOVA) highlighted that there was a statistically significant difference in the treatments for the mixing ratio tested. GAC-SBR results showed that treatment efficiency was dependent on landfill leachate concentration and hydraulic retention time (HRT). Coupled treatment tested exhibited a high potential for co-treatment of leachate and municipal wastewater. However, the effluent after treatment could not achieve a complete or very high level of COD, nutrients and turbidity removal which necessitates the incorporation of physico-chemical processes such as coagulation, electrocoagulation, membrane filtration etc. as post-treatment options. Further studies in this direction along with exploring the longevity of GAC in SBR would provide useful information for effective landfill leachate treatment.

Bipolar membrane electrodialysis for sustainable utilization of inorganic salts from the reverse osmosis concentration of real landfill leachate

Developing an effective resource utilization method for landfill leachate reverse osmosis concentrate (LLRC) remains a challenge because of the high concentrations of inorganic salts and refractory organic compounds. This study applied a bipolar membrane electrodialysis (BMED) to separate inorganic salts from real LLRC while simultaneously reclaiming inorganic acids and bases. The performance of BMED was affected by operating parameters, such as operating voltage, membrane surface flow velocity, and initial acid-base concentration. With optimized operating parameters, the reclaimed acid-base concentrations, desalination rate, and current efficiency were higher with less energy consumption. Ultimately, 0.41 mol/L acids and 0.40 mol/L bases were reclaimed from LLRC. The reclaimed acids contained 88 wt% HCl and 12 wt% HNO3. The reclaimed bases were 52 wt% NaOH and 45 wt% KOH. Furthermore, the concentrations of arsenic and heavy metals were low enough to safely utilize reclaimed products. The electromigration of organic compounds was controlled by protonation. After excluding the fixed costs, the net profit of 1 m3 LLRC treatment by BMED was $27.630, which showed remarkable economic feasibility. Our research offers a new strategy to realize sustainable utilization of inorganic salts from LLRC.

Analysis of Chrysopogon zizanioides used as floating treatment wetlands in the removal of heavy metals present in leachate

AbstractThe objective of this study was to evaluate the potential of Chrysopogon zizanioides using the floating wetland treatment (FWT) technique in the removal of As, Cd, Cr, Cu, Pb, Zn, Fe, and Hg from three different concentrations of landfill leachate (100% crude leachate [L100], 75% leachate + 25% tap water [L75], and 50% leachate + 50% tap water [L50]) for a period of 60 days. The concentration of heavy metals in leachate and C. zizanioides was analyzed by inductively coupled plasma optical emission spectrometry. The results show that heavy metal concentrations decrease significantly (p &lt; 0.05) in vegetation treatments. Removal efficiency was higher in the L100 leachate with 100%, 58.1%, 33.4%, 67.8%, 58.3%, 29.4%, 69.2%, and 67.2% for As, Cd, Cr, Cu, Fe, Hg, Pb, and Zn, respectively. This study demonstrates the efficiency of removing heavy metals from landfill leachate using the FWT technique.

Concentration of landfill leachate by solar driven surface vaporization performed on nanosecond-laser-treated titanium surface

The use of solar evaporators to concentrate landfill leachate is a sustainable approach for reducing wastewater volume and generating clean water. Recent studies have investigated numerous interfacial solar evaporators. However, achieving a high evaporation rate under low optical concentrations remains challenging. This research develops mono and bifacial titanium photo-thermal material for solar-based landfill leachate treatment. Its strong absorbency, photo-thermal, thermal insulation, and quick water delivery characteristics enable the fabricated material to reach a high evaporation rate, including 2.02 and 1.71 kg/h under one sun for double and single-sided panels, respectively. Under one sun for a single-sided panel, the photo-thermal conversion effectiveness reached nearly 80.00%, resulting in a high interfacial water evaporation efficiency of 86.00%. It was possible to easily position the fabricated photo-thermal panels at any angle and implement them to optimize irradiation from incidence light. In comparison with raw landfill leachate, the concentrated landfill leachate displayed high turbidity, total suspended solids, solid suspended concentration, and total dissolved solids. Additionally, in the purified water, 98.70%, 91.20%, and 99.70% removal efficiencies were obtained for Cr2+, Ni2+, and Fe2+. Besides, COD (chemical oxygen demand), TOC (total organic carbon), and NH3-N (ammonia nitrogen) were removed at 90.36%, 86.13%, and 69.3%, respectively. Based on the results of this study, the super-hydrophilic titanium photo-thermal material is a potential candidate solar absorber for simultaneously concentrating wastewater and producing clean water.

Long-term evaluation of the anaerobic co-digestion of food waste and landfill leachate to alleviate ammonia inhibition

To evaluate the feasibility of the co-digestion of food waste (FW) and landfill leachate (LL) to alleviate ammonia inhibition, a series of batch co-digestion experiments were conducted to explore the optimal substrate mixing ratio, and semi-continuous experiments were conducted to evaluate the long-tern effects of LL addition on methane generation and digestate characteristics of the anaerobic co-digestion system under ammonia stress. The optimum methane generation and digestate properties were observed when the concentration of LL in the dilution liquid in the co-digestion reactor was 40 % (v/v). Significant volatile fatty acid accumulation and lower methane yields were both observed during the long-term FW mono-digestion when the total ammonia nitrogen (TAN) concentration reached 3391.27 mg·L–1. However, stable methane generation was observed in the co-digestion system, even when the TAN was 3721.59 mg·L–1, confirming that the LL alleviated the ammonia inhibition of the FW-based anaerobic digestion (AD) system. Microbial analysis of the AD reactors demonstrated that the relative abundance of Pelotomaculum was higher in the co-digestion system than in the mono-digestion system. Analysis of the phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) confirmed the enrichment of genes involved in butyrate, propionate, and methane metabolism in the co-digestion system. In addition, analysis of the digestate characteristics (i.e., dewaterability, germination index, and heavy metals concentrations) indicated that there was no ecological risk for utilization of the digestate after long-term co-digestion operation. These results aim to provide guidance for using LL to promote the processing of FW in the future.

Optimization Research on Burner Arrangement of Landfill Leachate Concentrate Incinerator Based on “3T+E” Principle

At present, the treatment of landfill leachate is an unavoidable challenge facing environmental problems. Incineration is one of the effective methods to treat landfill leachate which meets the 3T+E principle and can avoid the production of dioxin in the process of treatment. Based on the 3T+E principle, this paper studied the influence of burner arrangement on the treatment of landfill leachate through the numerical simulation method. The research showed that the symmetrical arrangement of reverse swirl and same direction flow were more conducive to the combustion of landfill leachate concentrations in the incinerator so that the residence time of the flue gas in the second combustion chamber can also exceed 2 s. When the nozzle arrangement height is 0.9 m–0.8 m, the wall collision rate of concentrated liquid droplets can be reduced, and the burnout rate of landfill leachate was the highest, reaching more than 92%.

Optimization of pilot scale forward osmosis process integrated with electrodialysis to concentrate landfill leachate

A forward osmosis (FO) – electrodialysis (ED) pilot was built and tested for landfill leachate (LL) concentration and draw and water recovery. 70% water extraction from high salinity (35mS.cm−1) LL was achieved through FO in batch operation; no fouling or clogging were observed during the operation of the pilot. Operating with constant high salinity draw solution (>100 mS.cm−1) was required to reach 70% water extraction especially for the final step of LL concentration. FO allowed for high rejection (>90%) of most LL compounds and their effective concentration in the concentrated LL except for ammonium which was partially lost through the membrane or by stripping. Lowering the pH of the LL (from 8.3 down to 6.5) allowed to reduce losses by stripping but led to higher overall losses due to longer filtration time required (higher salinity of the feed solution following hydrochloric acid addition for neutralization). Ultimately, tests in continuous mode (one pass through the FO module) demonstrated that ammonium losses can be reduced significantly (below 15%), thus allowing for efficient operation in counter current mode, resulting also in a better usage of the osmotic pressure. Regeneration of the draw solution and production of a dilute water stream within the discharge requirements (<6 ms.cm−1) was achieved by ED. Energy consumption of the FO-ED system remain below 8 kWh.m−3 allowing the process to be energetically competitive in comparison with other LL concentration technologies and other FO hybrid systems.

Effect of leachate effluent water reuse on the phytotoxicity and micropollutants accumulation in agricultural crops

This research comparatively investigated the effects of effluents from three biological wastewater treatment systems on the phytotoxicity, seed germination, and accumulation of micropollutants and heavy metals in plants irrigated with the effluents under study. The three biological wastewater treatment systems were two-stage activated sludge (AS), two-stage moving bed bioreactor (MBBR), and two-stage moving bed bioreactor with microfiltration (MBBR/MF). The systems were operated in parallel with identical landfill leachate concentrations under different hydraulic retention time (HRT) (24, 18, and 12 h). The phytotoxicity experiments were carried out with golden pothos (Epipremnum aureum) planted in soil irrigated with AS, MBBR, and MBBR/MF effluent and those raised in the effluent (without soil). The malondialdehyde (MDA) concentrations in the plants were used to determine the plant stress. To evaluate the effect of water reuse to agricultural crops, this research measured the seed germination rates of lettuce (Lactuca sativa) irrigated with AS, MBBR, and MBBR/MF effluent and the accumulation of micropollutants and heavy metals. The results showed that under 24 h HRT, the AS, MBBR, and MBBR/MF systems could achieve high treatment efficiency of organics and nutrients and micropollutant degradation (73.4 – 100%). With shorter HRT (18 and 12 h), the treatment efficiency and micropollutant degradation of MBBR and MBBR/MF remained relatively unchanged (68.7 – 100%), unlike in the AS system. The MBBR/MF effluent exhibited the comparatively lowest MDA concentrations. Furthermore, the MBBR/MF effluent minimally affected the growth of lettuce, as evidenced by highest seed germination rates. No micropollutants and heavy metals were present in lettuce irrigated with MBBR/MF effluent. However, traces of bisphenol A and di-(ethylhexyl)-phthalate were detected in lettuce watered with AS and MBBR effluents. As a result, the MBBR/MF system is operationally and environmentally ideal for treating landfill leachate for high-quality effluent which can be reused to irrigate crop and replenish surface water.

Translocation factor of heavy metals by elephant grass grown with varying concentrations of landfill leachate.

The aim of this study is to obtain the translocation factor by application of landfill leachate (LL) diluted in public irrigation water (IW). Pennisetum purpureum Schum (elephant grass) was cultivated for 83 days in an experimental water reuse unit. The present work was developed at the Experimental Water Reuse Unit (UERA), on the UFERSA campus in Mossoró, RN, Brazil. Plot irrigation was based on water balance and crop evapotranspiration (ETc). The concentration in the plant tissue (root and leaf) of the following heavy metals was measured to determine the respective translocation factors: manganese (Mn), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd), and lead (Pb). The experiment was set up in a randomized block design with five treatments (T1, plots irrigated only with IW; T2, 50% of LL dose plus IW; T3, 100% of LL dose plus IW; T4, 150% of LL dose plus IW; and T5, 200% of LL dose plus IW) and five replications. All treatments received LL plus IW depth of 491.02 mm for 83 days of P. purpureum cultivation. The data obtained were submitted to multivariate analysis plus the nonparametric Kruskal-Wallis test to compare the means. Pennisetum purpureum showed a potential to accumulate metals in its tissues, mainly Mn, Zn, and Cu. The treatments that most favored the extraction of these metals were T2 and T5; in this sense, P. purpureum was not efficient in translocating heavy metals, since the translocation factor observed in all treatments was below 1.0, indicating that the species used extract heavy metals from soil solution and keeps in yours roots. This suggests planting P. purpureum may not be a viable option to remediate environments highly contaminated with heavy metals.

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 (&gt;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.

Chemical and geotechnical properties of solidified/stabilized MSWI fly ash disposed at a landfill in China

The chemical and geotechnical properties of solidified/stabilized (s/s) municipal solid waste incineration (MSWI) fly ash are of prime importance for the design and operation of landfill sites. This study conducted field and laboratory tests to investigate aging effects on the chemical and geotechnical properties of s/s MSWI fly ash. Field investigations included borehole sampling and cone penetration tests (CPTs), and laboratory analyses included the measurement of the chemical, physical, hydrological, and mechanical properties of s/s fly ash with different fill ages. The results showed that: 1) Cl concentrations in landfill leachate were as high as 52,700 mg.L−1, which may present a technical challenge for leachate treatment; 2) specific gravity decreased with fill age, which was attributed to the leaching of metal elements from the s/s fly ash; 3) mean particle size decreased with fill age, resulting in an increase in the gravimetric moisture retention capacity (MRC) and a decrease in the saturated hydraulic conductivity; 4) gravimetric MRC was much higher than the initial moisture content, suggesting water absorption by s/s fly ash after landfilling; and 5) shear strength decreased with fill age, which was consistent with the CPTs results. To improve the design and operation of s/s MSWI fly ash landfill sites, the following suggestions are made: 1) the use of concentrated MSW landfill leachate in the s/s fly ash process should be avoided to reduce the concentrations of subsequent landfill leachate; 2) leachate generation could be further reduced by improving landfill operation practices and by taking advantage of the absorption capacity of s/s fly ash; and 3) the specific geotechnical parameters of s/s fly ash should be obtained prior to the design of landfill sites, and their aging effects should also be taken into consideration.

LED lamps waste in Canada: Generation and characterization

Lamps and lighting products are the most commonly used electrical products around the globe. With the improvement in lamp technologies, products have grown complex and hence require an improved recycling process. Light emitting diode (LED) lamps consist of various valuable and hazardous metals such as copper, aluminum, iron, zinc, lead, arsenic, and antimony.This paper provides an estimation of the waste LED lamps generation in Canada. It shows that the cumulative waste from LED lamps is expected to reach 12 kT by 2021. A characterization of LED lamps was also conducted to estimate the metal concentration and landfill leachate toxicity characteristics, which have not yet been studied with a bulk sample. The results showed that aluminum is the major metal present in LED lamps with a concentration of over 22%, followed by iron, copper, and zinc. It also showed the presence of heavy metals such as lead, arsenic, and antimony. On the contrary to the previous study, the landfill leachate concentration for waste LED lamps was found to be lower than the British Columbia (BC) landfill limits for all metals.

Anaerobic co-digestion of industrial landfill leachate and glycerin: methanogenic potential, organic matter removal and process optimization

ABSTRACT The objective of this study was to evaluate the performance of the anaerobic co-digestion of different concentrations of industrial landfill leachate associated with crude residual glycerin, in relation to the methanogenic potential, COD removal, accumulated methane production, the effects of the factors (food/microorganism ratio and percentage of glycerin added to the leachate) and their interactions on kinetic parameters of methane production (CH4) using the modified Gompertz model. Co-digestion tests were carried out in bench scale (400 mL of useful volume) under batch mode at 30 ± 1°C during 30-day incubation of anaerobic sewage sludge as inoculum. The parameters glycerin addition to the leachate (v/v) (0%, 1.5%, 5%, 8.5% and 10%) and F/M ratio (0.3, 0.5, 1, 1.5 and 1.7) were investigated using Central Composite Rotational Design method (CCRD). The results indicated significant effect to the response variables: methanogenic potential, COD removal, accumulated production of CH4 and maximum estimated production of CH4, considering a confidence interval of 95% (p < .05). The ideal mixture of 95.13% of leachate with 4.87% of raw glycerin was obtained by desirability test to F/M of 1.61 gCOD of substrate per gVSS (volatile suspended solids) of sludge. Methanogenic potential was 0.19 LNCH4 gTVSrem −1, and the average removal of COD was 92%, resulting in accumulated production and maximum estimated production of CH4 of 74 and 80 mL, respectively. It was noted that the process of co-digestion of the industrial landfill leachate with the crude residual glycerin is promising, due to is potential of complementing and balancing organic materials, nutrients and other components that influence the biological process. Abbreviations: AN: ammoniacal nitrogen; BMP: biochemical methane potential; CCRD: central composite rotational design; COD: chemical oxygen demand; F/M ratio: food/microorganism ratio; FSS: fixed suspended solids; NTP: normal temperature and pressure; TSS: total suspended solids; TA: total alkalinity; TFS: total fixed solids; TKN: total Kjeldahl nitrogen; TP: total phosphorus; TS: total solids; TVA: total volatile acids; TVS: total volatile solids; VSS: volatile suspended solids; WWTP: wastewater treatment plant