High Ammonia Landfill Leachate Research Articles

Comparison of long-term performances and final microbial compositions of anaerobic reactors treating landfill leachate

Laboratory scale anaerobic upflow filter, sludge blanket and hybrid bed reactors were operated for 860 days in the treatment of high ammonia landfill leachate. Organic loading was gradually increased from 1.3 to 23.5 kg COD/m 3 day in the start-up period and then fluctuated according to the COD concentration of raw leachate. To prevent free ammonia inhibition, influent pH was reduced to 4.5 after Day 181 and consequently COD removal efficiencies above 80% were achieved in all reactors. However, the anaerobic filter and hybrid bed reactor were generally found slightly more efficient and stable than the UASB reactor. In addition to conventional anaerobic reactor control parameters, the complementary techniques of denaturing gradient gel electrophoresis (DGGE), cloning and fluorescent in situ hybridization (FISH) were used to identify and compare the microbial profiles in the reactors at Day 830. Molecular analyses revealed that acetoclastic Methanosaeta species were prevalent in all reactors and configuration did not have an impact on microbial diversity in the long-term.

Molecular Analysis of Microbial Communities in Nitrification and Denitrification Reactors Treating High Ammonia Leachate

Molecular analysis of microbial populations in two bench-scale nitrification and denitrification reactors fed with high ammonia landfill leachate was conducted in this study by using DGGE, cloning, and FISH techniques in addition to classical efficiency control parameters. Nitrification tank was operated with a computer-controlled alkalinity dosing system to supply the alkalinity intermittently as consumed on the basis of on-line pH monitoring. By keeping the pH at 7.0 with this system, 99% nitrification efficiency and rates of about 0.14–0.18 mg-N/mgVSS day were obtained. Meanwhile, as ammonia oxidizing bacteria Nitrosomonas and Nitrosococcus mobilis-like cells and as nitrite oxidizing bacteria Nitrobacter-related cells were intensively indicated. Moreover, some aerobic denitrifiers as Thauera species were also identified. After the termination of pH adjustment in the preceding anaerobic reactors, nitrification tank was loaded with more biodegradable COD as a result of reduced COD removal in anaerobic reactors. Microbial diversity was immediately affected from this alteration and heterotrophic carbonaceous bacteria and aerobic denitrifiers have dominated. To provide the former high efficiencies, retention time has increased from 24 to 48 h and a second pump dosing HCl was included to the automatic control system. Subsequent to these precautions, numbers of ammonia (Nso190) and nitrite oxidizing bacteria (NIT3) were comparatively increased. In denitrification system, about 98% denitrification efficiencies were obtained at 2000 mg/L NO x -N concentrations if sodium acetate was supplied as carbon source. Meanwhile, with 20 gVSS/l biomass concentration, denitrification rates of about 1.34 mgNO x -N/mgVSS day were obtained. All sludge samples have represented similar DGGE patterns and Paraccoccus-related species were identified as dominant denitrifying bacteria.

Investigation of variations in microbial diversity in anaerobic reactors treating landfill leachate

A young landfill leachate containing elevated total ammonia concentrations frequently as high as 2,700 mg/l was anaerobically treated for 1,015 days in two different laboratory-scale anaerobic reactors configured as sludge blanket and hybrid bed. In this paper, the last 265 days of this long-term anaerobic treatability study are presented. Effects of high ammonia concentrations on reactor performances were correlated to the variations in microbial diversity by identifying the dominant microorganisms with FISH (fluorescent in-situ hybridization), cloning, DGGE (denaturing gradient gel electrophoresis) and morphological analysis. The results have indicated that the high ammonia landfill leachate can be treated successfully by using either an UASB or a hybrid bed reactor if temporary pH adjustments in the reactor influents are made when high ammonia concentrations are experienced. Consequently, COD removal efficiency is independent of microbial diversity and reactor configuration and it depends on the biodegradable portion of the leachate. Under this circumstance, stability of the reactors with low levels of acetate was supported by the abundance of Methanosaeta population. In both of the reactors, some populations of Methanobacteriaceae were also detected while other methanogenic species were virtually absent. However, after the termination of pH adjustment at Day 860, reactors immediately became unstable due to the sudden increase in free ammonia concentration up to 400 mg/l. COD removal efficiency decreased to 42% in the hybrid bed and to 48% in the UASB reactor. The durations of inhibitions were not long enough to severely deteriorate the massive Methanosaeta cells; therefore, many of them were again identified after two free ammonia inhibitions. However, subsequently, long filamentous morphologies of Methanosaeta cells shifted to shorter filaments and they lost their aggregating property.

The effect of decreased ambient temperature on the biological nitrification and denitrification of a high ammonia landfill leachate

This research investigated the nitrogen removal capabilities of a pre- and post-denitrification process, when treating sanitary landfill leachate containing an ammonia concentration of over 2200mg N/L, at operating temperatures down to 10°C. The treatment system employed is generally known as a 4-Stage Bardenpho process. Two parallel systems were operated throughout the study; each system had an aerobic solids retention time of 20 days and an external recycle ratio (return activated sludge) of about 3:1. During the entire experimental period, one system used an internal recycle ratio of about 4:1, while the other system used one of 3:1. Methanol was used as supplementary carbon source for denitrification. When operating temperature was decreased from 20 to 17°C, an approximate 15% decrease in denitrification was immediately experienced within both systems, with no noticeable affect on nitrification. This was an unexpected result. Subsequently, the temperature was further decreased to 14°C, and finally to 10°C. With the temperature at 14°C, aerobic wasting was also stopped and methanol loading was progressively decreased to match actual denitrification requirements. At 10°C, both systems suffered major nitrification and denitrification inhibition. Changes in operating parameters, such as a decrease in influent ammonia and methanol loading, as well as an increase in ambient temperatures, from 10 to 15°C, did not significantly improve overall system performance, within a reasonable time frame. Both denitrification and nitrification problems were mainly attributed to decreased ambient temperature, although other possible factors were noted; at project completion, about 50% of the incoming ammonia was being removed across the system.

A Pre- and Post-Denitrification System Treating a Very High Ammonia Landfill Leachate: Effects of pH Change on Process Performance

The prime objective of this research was to investigate the nitrogen removal capabilities of a pre- and post-denitrification process, when treating landfill leachate containing an ammonia concentration of over 2200 mg N l−1. The treatment system, also known as a 4-Stage Bardenpho process, was operated with an external recycle ratio of 3:1 and an internal recycle ratio of 4:1. The first anoxic reactor actual hydraulic retention time was 1.5 hours, while the first aerobic retention time was 3 hours. The very high ammonia concentration was simulated by pumping ammonium chloride into the first anoxic reactor of the system. Methanol was used as the organic carbon source for denitrification. At an influent ammonia concentration of about 2200 mg N l−1, the anoxic pH levels stabilized at about 8.6 within the first reactor, and at about 9.8 within the second reactor. These high anoxic pH levels were partially responsible for decreased denitrification and, hence, residual NOx concentrations in the effluent. By decreasing the pH in the anoxic basins, the overall performance of the system immediately improved; the effluent NOx concentration decreased rapidly over a period of about six days, from an average 80 mg N l−1 to about 60 mg N l−1, with some samples as low as 40 mg N l−1. Subsequently, increased leachate toxicity resulted in an unexpected system failure; although the treatment system eventually recovered and stabilized, denitrification in each anoxic reactor remained at only about 55%, with final effluent NOx concentrations of over 100 mg N l−1. Despite this reduced level of performance, the decrease in anoxic pH resulted in enhanced nitrification performance, complete ammonia removal in the first aerobic reactor, and a more stable, overall performance in the 4-Stage Bardenpho process.

Exceptionally high-rate nitrification in sequencing batch reactors treating high ammonia landfill leachate

The nitrogen removal capacity of a suspended culture system treating mature landfill leachate was investigated. Leachate containing high ammonium levels of 300-900 mg N/L was nitrified in a bench scale sequencing batch reactor. Leachate from four different landfills was treated over a two year period for the removal of nitrogen. In this time, a highly specific nitrifying culture was attained that delivered exceptionally high rates of ammonia removal. No sludge was wasted from the system to increase the throughput and up to 13 g/L of MLSS was obtained. Settleability of the purely nitrifying biomass was excellent with SVI less than 40 mL/g, even at the high sludge concentrations. Nitrification rates up to 246 mg N/(L h) (5.91 g N/(L d)) and specific nitrification rates of 36 mg N/(gVSS h) (880 mg N/(gVSS d)) were obtained. The loading to the system at this time allowed complete nitrification of the leachate with a hydraulic retention time of only 5 hours. Following these successful treatability studies, a full-scale plant was designed and built at one of the landfills investigated.

Biological nitrification and denitrification of a simulated high ammonia landfill leachate using 4-stage Bardenpho systems: system startup and acclimation

This research investigated the nitrogen removal capability of two biological nitrification systems, with pre- and post-denitrification, when treating a landfill leachate characterized by high ammonia concentrations and low levels of biodegradable organics. The recycle ratios of the systems were set so that, at an average influent flow of 10 L/d, the actual hydraulic retention time of the first anoxic reactor was about 1.5 h for one system and 1.7 h for the other system. The systems also operated at a first aerobic reactor actual hydraulic retention time of 3 and 3.4 h, respectively. Methanol was used as a supplementary organic carbon source for denitrification. High leachate ammonia concentrations were simulated by artificially increasing influent ammonia to about 2200 mg N/L. This paper presents an overview of initial startup and acclimation, as well as some of the direct and indirect effects of methanol addition on process performance. The reported data were collected during two runs at incrementally increasing influent ammonia concentrations. During the first run to reach 2200 mg N/L, methanol loading rates were increased concomitantly with ammonia loading rates, to match expected aerobic NOx production, using a CH3OH:NOx of about 20:1. This resulted in methanol carry-over into the first aerobic zone, enhanced aerobic heterotrophic growth, and further inhibition of the nitrifying population, already inhibited by recycling through the elevated "free" ammonia levels of the first anoxic zone. When these systems were allowed to adapt up to 14 days, rather than 7 days, initially, to each incremental ammonia increase, and with methanol loading rates subsequently changed to yield CH3OH:NOx of only 5:1, the influent ammonia concentration was increased to approximately 2200 mg N/L within 88 days from the start of the second run, without any inhibitory problems. The timing and levels of ammonia and methanol loading rate increases, with respect to each other and to the corresponding previous loading rate increase, played an important role in system stability and the onset of nitrification failure.Key words: biological treatment, high ammonia leachate treatment, denitrification, methanol, nitrification.

Biological nitrification and denitrification of a simulated high ammonia landfill leachate using 4-stage Bardenpho systems: system startup and acclimation

Biological nitrification and denitrification of a simulated high ammonia landfill leachate using 4-stage Bardenpho systems: system startup and acclimation

Pre-denitrification and pre- and post-denitrification treatment of high-ammonia landfill leachate

This bench-scale study investigated the nitrogen-removal capabilities of two different biological process configurations treating methanogenic-state landfill leachate containing up to 1200 mg N/L of ammonia. The first configuration was a pre-denitrification system known as the modified Ludzack-Ettinger (MLE) process. Large clarifier sludge recycle flows, set to yield clarifier recycle ratios of 7:1 and 8:1, were evaluated as a means to reduce effluent NOx concentrations. A pre- and post-denitrification system, known as the four-stage Bardenpho process, was the second configuration evaluated. The MLE systems (20 day aerobic solids retention time (SRT)) were capable of producing effluent containing about 50 mg N/L of ammonia and 200-235 mg N/L of total inorganic nitrogen (ammonia + NOx) when treating leachate containing approximately 1200 mg N/L of ammonia. In contrast, effluent from the four-stage Bardenpho system contained less than 1 mg N/L of ammonia and 15 mg N/L of NOx, when treating 1100 mg N/L ammonia leachate. An aerobic number 1 SRT of 20 days (total aerobic SRT approximately equal to 40 days) was used with aerobic number 1 and clarifier sludge recycle ratios of 4:1 and 3:1, respectively. The ammonia-removal potential of both systems was clearly demonstrated but each system also showed certain disadvantages, characteristic of each process.Key words: ammonia-N, anoxic denitrification, leachate treatment, nitrification, pre-denitrification.

Pre-denitrification and pre- and post-denitrification treatment of high-ammonia landfill leachate

Pre-denitrification and pre- and post-denitrification treatment of high-ammonia landfill leachate

Chromium and nickel toxicity during the biotreatment of high ammonia landfill leachate

Two nitrification‐denitrification systems were used to determine the possible inhibitory and/or toxic effects of supplemental chromium and nickel addition to the nitrification‐denitrification process in the treatment of a relatively high ammonia, low biodegradable carbon, municipal landfill leachate. Results indicated that chromium (Cr+3) and nickel (Ni+2) caused inhibitory effects to the system at soluble concentrations of approximately 0.30 and 0.70 mg/L, respectively. Chromium affected both the nitrification and denitrification process, whereas nickel impaired only the nitrification performance; denitrification was unaffected at the nickel concentrations used. The failures were believed to be due to either the soluble metal levels themselves or the buildup of metals in the solids, although lack of long‐term acclimation cannot be ruled out. No phosphorus deficiency was noted in either case. This ruled out the possibility of system failures due to lack of bioavailable phosphorus, as reported with zinc in the early stages of this study.

High ammonia landfill leachate treatment using anaerobic filter and rotating biological contactor

A pre-denitrifying anaerobic filter and a rotating biological contactor (RBC) were used to remove nitrogen from a high ammonia landfill leachate collected from a municipal and industrial solid waste landfill in Kaohsiung, Taiwan, Republic of China. The research indicated that greater than 95% ammonia removal from high ammonia-N (2140 mg/L) leachate can be achieved with RBC ammonia-N loading rates up to 1.5 g/(m2∙d). At RBC loading rates of 1.5–3.0 g/(m2∙d), ammonia removal ranged from 80% to 90%. Nitrogen removal averaged 66%, including an estimated 54% removal in the RBC. Nitrogen removal in the RBC was the result of either simultaneous nitrification and denitrification or air stripping of ammonia in combination with nitrification. Both alkalinity consumption and COD removal results support the explanation of simultaneous nitrification and denitrification (potentially aerobic denitrification); but since RBC off-gasses were not monitored, neither theory can be confirmed. The high nitrogen removal in the RBC suggests that for this leachate the anaerobic filter was not required for ammonia and nitrogen removal. BOD and COD removal averaged 92% and 49% respectively. Key words: landfill, leachate, treatment, ammonia, rotating biological contactor (RBC), nitrification, denitrification.

The effect of ammonia loading and operating temperature on nitrification and denitrification of a high ammonia landfill leachate

The effect of ammonia loading and operating temperature on the treatment of high ammonia, methanogenic, landfill leachate was investigated. Two single-sludge, nitrification–predenitrification systems were operated in parallel: one with a 10-day aerobic solids retention time, and the other with a 20-day aerobic solids retention time. The study consisted of two phases: an ammonia loading phase and a cold temperature phase. From the first phase, it was found that, at an influent leachate ammonia level of up to 1500 mg N/L, both systems produced an effluent of < 1 mg NH4-N/L and approximately 170 mg NOx−-N/L. Aerobic nitrite and anoxic "free" ammonia were both observed to increase as the ammonia loading was increased. When the influent ammonia was raised from 1500 to 2000 mg N/L, nitrification in both systems failed. During the second phase, the temperature was decreased from 20 to 10 °C while maintaining the leachate ammonia level at 1500 mg N/L. Aerobic nitrite accumulation and rising aerobic BOD5 were observed to begin at 14 °C. When the temperature was dropped from 12 to 10 °C, nitrification failed in both systems. In both cases, nitrification was re-established at 10 °C, by ceasing to waste solids and by stopping methanol addition. Key words: ammonia, biological, denitrification, landfill, leachate, nitrification, temperature, treatment.

Inferred metal toxicity during the biotreatment of high ammonia landfill leachate

ABSTRACT: Two nitrification‐denitrification systems were used to determine the possible inhibitory and/or toxic effects of supplementa metals addition to the nitrification‐denitrification process in the treatment of a relatively high ammonia, low biodegradable carbon, municipa landfill leachate. The addition of metals likely resulted in the precipitation of phosphorus which caused the nitrification‐denitrification process to be inhibited due to the deficiency of bioavailable phosphorus. Even though the phosphorus concentrations in mixed liquor and system effluent samples filtered through Whatman No. 4 filters or glass‐fiber filters appeared to be adequate, it was discovered that they were considerably lower when filtered through 0.45‐µm membrane filters. This seemed to indicate that although some of the precipitated phosphorus passed through the Whatman No. 4 filter, it was not available as a nutrient for microbial metabolism. Therefore, only the phosphorus that will pass through a 0.45‐µm membrane filter, and is defined as soluble in Standard Methods (1985) is readily available to the microorganisms. This should be monitored ensure sufficient nutrient availability in nitrification‐denitrification treatment systems potentially exposed to metals capable of precipitating phosphorus. It is recommended that a minimum soluble phosphorus concentration of 0.5 mg/L be maintained to ensure adequate phosphorus for nitrification and denitrification; in addition, when conducting activated sludge metal toxicity studies, total or Whatman No. 4‐filtered samples should not be used to determine the presence of adequate phosphorus.