Anaerobic treatment of landfill leachate by sulfate reduction

The present study was conducted to investigate the effectiveness of the sulphate-reduction pathway in the anaerobic treatment of landfill leachate. The effects of several COD/SO4 ratios (keeping COD constant) and loadings on anaerobic filter performance were studied and compared with the results from anaerobic filters which followed the methanogenic pathway. Results indicated that the treatability of leachate by sulphate reducing bacteria (SRB) was dependent upon the leachate strength. With high strength leachate (COD=15000 mg/L) from the Keele Valley Landfill, it was found that at lower COD/SO4 ratios (≤1.6) toxic conditions developed in the system that were more inhibitory to the SRB than to the methane producing bacteria (MPB). As the COD/SO4 ratio increased, methanogenesis predominated. No predominance of SRB occurred at any COD/SO4 ratio with high strength leachate. The highest COD removal achieved was about 70% of which 20% was accomplished by the SRB at a COD/SO4 ratio of 1.6 and an organic loading rate (OLR) of 4 kg COD/m3.d. With low strength leachate (COD=1500-3300 mg/L) from the Brock West Landfill, and a COD/SO4 ratio <1, SRB became predominant. In these anaerobic filters in which SRB were predominant, the SRB reduced the COD as well as the MPB could. Sulphide inhibition did not take place at any loading in units treating low strength leachate. Consequently, both SRB and MPB should function at COD/SO4 ratios between 1 and 3. About 60% COD removal was achieved at a loading of 2.8 kg COD/m3.d and a COD/SO4 ratio of 1.0. However at a loading of 6 kg COD/m3.d only 27% COD removal was achieved, all of it through the sulphate-reduction pathway. These OLR values are comparable to those applied in systems where methanogenesis was dominant. It was also observed that once the methanogens were established in the units, it was not possible to displace them completely. However, where methanogenesis had not been previously established, it was found that sulphate-reduction could be the sole pathway for COD removal. From this study, it can be concluded that there is no advantage to the sulphate-reduction pathway in the anaerobic treatment of landfill leachate. The other options for increasing the loadings, i.e. the use of high surface/volume filter media (to achieve higher biomass concentrations) or high rate systems are likely to be more successful.

Download Full-text

Psychrophilic anaerobic treatment of low strength wastewaters

Water Science & Technology ◽

10.2166/wst.1999.0240 ◽

1999 ◽

Vol 39 (5) ◽

pp. 203-210 ◽

Cited By ~ 24

Author(s):

Salih Rebac ◽

Jules B. van Lier ◽

Piet Lens ◽

Alfons J. M. Stams ◽

Freddy Dekkers ◽

...

Keyword(s):

Fatty Acids ◽

Volatile Fatty Acids ◽

Oxygen Demand ◽

Granular Sludge ◽

Anaerobic Treatment ◽

Cod Removal ◽

High Rate ◽

Organic Loading Rate ◽

Substrate Conversion ◽

Low Strength

Psychrophilic (2 to 20°C) anaerobic treatment of low strength synthetic and malting wastewater was investigated using a single and two module expanded granular sludge bed (EGSB) reactor system. The chemical oxygen demand (COD) removal efficiencies found in the experiments exceeded 90 % in the single module reactor at an organic loading rate up to 12 g COD dm−3 day−1 and a HRT of 1.6 h at 10-12°C ambient temperature using influent concentrations ranging from 500 to 800 mg COD dm−3. When a two module EGSB system was used at the temperature range 10-15°C, soluble COD removal and volatile fatty acids removal of 67-78% and 90-96% were achieved, respectively, and an OLR between 2.8-12.3 kg COD m−3 day−1 and a HRT of 3.5 h. The second module serves mainly as a scavenger of non-degraded volatile fatty acids (VFA) from the first module. The optimal temperatures for substrate conversion of reactor sludge, after it has been exposed to long term psychrophilic conditions, were similar to those of the original mesophilic inoculum. The specific activities of the sludge in the reactor increased in time by a factor 3, indicating enrichment of methanogens and acetogens even at low temperatures. By adapting the process design to the expected prevailing conditions inside the reactor, the loading potentials and overall stability of the anaerobic high-rate process may be distinctly improved under psychrophilic conditions. The results obtained clearly reveal the big potentials of anaerobic wastewater treatment under low ambient (10-12°C) temperature conditions for low strength wastewaters, very likely including domestic sewage.

Download Full-text

Anaerobic treatment of a municipal landfill leachate

Canadian Journal of Microbiology ◽

10.1139/m97-135 ◽

1997 ◽

Vol 43 (10) ◽

pp. 937-944 ◽

Cited By ~ 2

Author(s):

Jean-Claude Frigon ◽

Jean-Guy Bisaillon ◽

Gilles Paquette ◽

Réjean Beaudet

Keyword(s):

Landfill Leachate ◽

Growth Parameters ◽

Oxygen Demand ◽

Anaerobic Treatment ◽

Cod Removal ◽

Organic Loading Rate ◽

Oil And Grease ◽

Municipal Landfill ◽

Fixed Film ◽

Film Reactor

Leachate from a municipal landfill site was treated in a laboratory using fixed-film cultures under anaerobic conditions. Serum-bottle cultures were used for optimization of the growth parameters. The reduction of the chemical oxygen demand (COD) of the leachate was faster at 29 °C compared with lower temperatures. Gradual acclimation of the microbial population to temperatures as low as 4 °C considerably increased the rate of COD removal at these temperatures. Addition of supplements to the leachate was not needed and it was not necessary to adjust the pH (5.9) for optimal COD reduction. Continuously fed reactors were also used to treat the leachate. The maximum organic loading rate of the reactor at 22 °C to obtain 85% COD removal was 2.1 kg COD∙m−3∙day−1, which corresponded to an hydraulic retention time of 1.5 days. After treatment under these conditions, the toxicity (Microtox method) of the leachate was completely eliminated and the required quality standards were met for iron, oil and grease, and phenols. The fermentative microorganisms in the biofilm of the reactor were evaluated to 4.6 × 107cells∙cm−2and identified as Streptococcus gallinarum, Clostridium glycolicum, Clostridium bifermentans or sadallii, Citrobacter amalonaticus, Bacteroides capillosus, and Eubacterium sp.Key words: anaerobic treatment, landfill, leachate, growth parameters, fixed-film reactor, microbiology.

Download Full-text

Anaerobic Treatment of Polyethylene Terephthalate (PET) Wastewater from Lab to Full Scale

Water Science & Technology ◽

10.2166/wst.1999.0426 ◽

1999 ◽

Vol 40 (8) ◽

pp. 229-236 ◽

Cited By ~ 4

Author(s):

F. Fdz-Polanco ◽

M. D. Hidalgo ◽

M. Fdz-Polanco ◽

P. A. García Encina

Keyword(s):

Polyethylene Terephthalate ◽

Loading Rate ◽

Treatment Plant ◽

Textile Wastewater ◽

Anaerobic Treatment ◽

Cod Removal ◽

Organic Loading Rate ◽

Foam Formation ◽

Organic Loading ◽

Start Up

In the last decade Polyethylene Terephthalate (PET) production is growing. The wastewater of the “Catalana de Polimers” factory in Barcelona (Spain) has two main streams of similar flow rate, esterification (COD=30,000 mg/l) and textile (COD=4000 mg/l). In order to assess the anaerobic treatment viability, discontinuous and continuous experiments were carried out. Discontinuous biodegradability tests indicated that anaerobic biodegradability was 90 and 75% for esterification and textile wastewater. The textile stream revealed some tendency to foam formation and inhibitory effects. Nutrients, micronutrients and alkali limitations and dosage were determined. A continuous lab-scale UASB reactor was able to treat a mixture of 50% (v) esterification/textile wastewater with stable behaviour at organic loading rate larger than 12 g COD/l.d (0.3 g COD/g VSS.d) with COD removal efficiency greater than 90%. The start-up period was very short and the recuperation after overloading accidents was quite fast, in spite of the wash-out of solids. From the laboratory information an industrial treatment plant was designed and built, during the start-up period COD removal efficiencies larger than 90% and organic loading rate of 0.6 kg COD/kg VSS.d (5 kg COD/m3.d) have been reached.

Download Full-text

Sequenced anaerobic-aerobic treatment of high strength, strong nitrogenous landfill leachates

Water Science & Technology ◽

10.2166/wst.2004.0768 ◽

2004 ◽

Vol 49 (5-6) ◽

pp. 301-312 ◽

Cited By ~ 12

Author(s):

S.V. Kalyuzhnyi ◽

M.A. Gladchenko

Keyword(s):

Loading Rate ◽

High Strength ◽

Cod Removal ◽

Organic Loading Rate ◽

Inorganic N ◽

Landfill Leachates ◽

Total N ◽

N Removal ◽

Biological Nitrogen ◽

Uasb Reactors

As a first step in treatment of high strength, strong nitrogenous landfill leachates (total COD - 9.66-20.56 g/l, total nitrogen 780-1,080 mg/l), the performance of laboratory UASB reactors has been investigated under sub-mesophilic (19±3°C) and psychrophilic (10±2°C) conditions. Under hydraulic retention time (HRT) of around 1.2 days, when the average organic loading rate (OLR) was around 8.5 g COD/l/day, the total COD removal accounted for 71% (on average) for sub-mesophilic regime. The psychrophilic treatment conducted under the average HRT of 2.44 days and the average OLR of 4.2 g COD/l/day showed an average total COD removal of 58% giving effluents more suitable for subsequent biological nitrogen removal. Both anaerobic regimes were quite efficient for elimination of heavy metals by concomitant precipitation in the form of insoluble sulphides inside the sludge. The subsequent submesophilic aerobic-anoxic treatment of submesophilic anaerobic effluents led to only 75% of total inorganic N removal due to COD deficiency for denitrification created by too efficient anaerobic step. On the contrary, psychrophilic anaerobic effluents (richer in COD compared to the submesophilic ones) were more suitable for subsequent aerobic-anoxic treatment giving the total N removal of 95 and 92% at 19 and 10°C, respectively.

Download Full-text

Effect of organic loading rate on a wastewater treatment process combining moving bed biofilm and membrane reactors

Water Science & Technology ◽

10.2166/wst.2005.0664 ◽

2005 ◽

Vol 51 (6-7) ◽

pp. 421-430 ◽

Cited By ~ 24

Author(s):

E. Melin ◽

T. Leiknes ◽

H. Helness ◽

V. Rasmussen ◽

H. Ødegaard

Keyword(s):

Membrane Fouling ◽

Loading Rate ◽

Biofilm Reactor ◽

Cod Removal ◽

High Rate ◽

Organic Loading Rate ◽

Membrane Pore ◽

Moving Bed ◽

Loading Rates ◽

Removal Efficiencies

The effect of moving bed biofilm reactor (MBBR) loading rate on membrane fouling rate was studied in two parallel units combining MBBR and membrane reactor. Hollow fiber membranes with molecular weight cut-off of 30 kD were used. The HRTs of the MBBRs varied from 45 min to 4 h and the COD loading rates ranged from 4.1 to 26.6 g COD m−2 d−1. The trans-membrane pressure (TMP) was very sensitive to fluxes for the used membranes and the experiments were carried out at relatively low fluxes (3.3–5.6 l m−2 h−1). Beside the test with the highest flux, there were no consistent differences in fouling rate between the low- and high-rate reactors. Also, the removal efficiencies were quite similar in both systems. The average COD removal efficiencies in the total process were 87% at 3–4 h HRT and 83% at 0.75–1 h HRT. At high loading rates, there was a shift in particle size distribution towards smaller particles in the MBBR effluents. However, 79–81% of the COD was in particles that were separated by membranes, explaining the relatively small differences in the removal efficiencies at different loading rates. The COD fractionation also indicated that the choice of membrane pore size within the range of 30 kD to 0.1 μm has very small effect on the COD removal in the MBBR/membrane process, especially with low-rate MBBRs.

Download Full-text

Application of response surface methodology to optimize the COD removal efficiency of an EGSB reactor treating poultry slaughterhouse wastewater

Water Practice & Technology ◽

10.2166/wpt.2019.032 ◽

2019 ◽

Vol 14 (3) ◽

pp. 507-514 ◽

Cited By ~ 1

Author(s):

Y. Williams ◽

M. Basitere ◽

S. K. O. Ntwampe ◽

M. Ngongang ◽

M. Njoya ◽

...

Keyword(s):

Response Surface Methodology ◽

Response Surface ◽

Removal Efficiency ◽

Treatment Process ◽

High Strength ◽

Cod Removal ◽

Organic Loading Rate ◽

Wastewater Treatment Process ◽

Slaughterhouse Wastewater ◽

Cod Removal Efficiency

Abstract The poultry slaughterhouse industry consumes a large volume of potable water for bird processing and equipment cleaning, which culminates in the generation of high strength poultry slaughterhouse wastewater (PSW). The wastewater contains high concentrations of organic matter, suspended solids, nitrogen and nutrients. Most poultry slaughterhouses in South Africa (SA) discharge their wastewater into the municipal sewer system after primary treatment. Due to its high strength, PSW does not meet SA's industrial discharge standards. Discharge of untreated PSW to the environment raises environmental health concerns due to pollution of local rivers and fresh water sources, leading to odour generation and the spread of diseases. Thus, the development of a suitable wastewater treatment process for safe PSW discharge to the environment is a necessity. In this study, a biological PSW treatment process using an Expanded Granular Sludge Bed (EGSB) was evaluated. Response surface methodology coupled with central composite design was used to optimize the performance of the EGSB reactor. The dependant variable used for optimization was chemical oxygen demand (COD) removal as a function of two independent variables, hydraulic retention time (HRT) and organic loading rate (OLR). The interactions between HRT, OLR and COD removal were analysed, and a two factorial (2FI) regression was determined as suitable for COD removal modelling. The optimum COD removal of 93% was achieved at an OLR of 2 g-COD/L/d and HRT of 4.8 days. The model correlation coefficient (R2) of 0.980 indicates that it is a good fit and is suitable for predicting the EGSB's COD removal efficiency.

Download Full-text

Role of syntrophic microbial communities in high-rate methanogenic bioreactors

Water Science & Technology ◽

10.2166/wst.2012.192 ◽

2012 ◽

Vol 66 (2) ◽

pp. 352-362 ◽

Cited By ~ 69

Author(s):

Alfons J. M. Stams ◽

Diana Z. Sousa ◽

Robbert Kleerebezem ◽

Caroline M. Plugge

Keyword(s):

Fatty Acid ◽

Industrial Wastewater ◽

Microbial Community Composition ◽

Methanogenic Archaea ◽

High Strength ◽

Cost Effective ◽

Anaerobic Treatment ◽

High Rate ◽

Degrading Bacteria

Anaerobic purification is a cost-effective way to treat high strength industrial wastewater. Through anaerobic treatment of wastewaters energy is conserved as methane, and less sludge is produced. For high-rate methanogenesis compact syntrophic communities of fatty acid-degrading bacteria and methanogenic archaea are essential. Here, we describe the microbiology of syntrophic communities in methanogenic reactor sludges and provide information on which microbiological factors are essential to obtain high volumetric methane production rates. Fatty-acid degrading bacteria have been isolated from bioreactor sludges, but also from other sources such as freshwater sediments. Despite the important role that fatty acid-degrading bacteria play in high-rate methanogenic bioreactors, their relative numbers are generally low. This finding indicates that the microbial community composition can be further optimized to achieve even higher rates.

Download Full-text

High-strength ethylene glycol wastewater treatment in anaerobic polyvinyl alcohol gel beads based biofilm reactor

Global NEST Journal ◽

10.30955/gnj.001751 ◽

2015 ◽

Vol 18 (1) ◽

pp. 47-55

Keyword(s):

Ethylene Glycol ◽

Polyvinyl Alcohol ◽

Settling Velocity ◽

Loading Rate ◽

High Strength ◽

Biofilm Reactor ◽

Cod Removal ◽

Organic Loading Rate ◽

Gel Beads ◽

Pva Gel

<div> In this paper, ethylene glycol wastewater (EGW) treatment was studied by using one anaerobic polyvinyl alcohol (PVA) gel beads based biofilm reactor. Enhanced by PVA-gel beads based biofilm, organic loading rate (OLR) about 11 g COD l-1 d-1 was achieved at the end of this study. Black PVA-gel beads with an average settling velocity 322 m h-1 (9 cm s-1) and 0.24g VSS g-1 PVA gel mainly composed of Methanosarcina spp. were got, while no natural granules were found in this experiment. The COD removal efficiency in this study could reach a high value about 95%. Most COD removal was contributed by the PVA-gel beads based biofilm. It could be concluded that the PVA-gel beads based biofilm reactor is appropriate for EGW treatment. </div>

Download Full-text

Denitrification of Landfill Leachate by the Modified Rotating Biological Contactor (RBC)

Water Science & Technology ◽

10.2166/wst.1991.0600 ◽

1991 ◽

Vol 23 (7-9) ◽

pp. 1477-1485 ◽

Cited By ~ 9

Author(s):

Masaaki Hosomi ◽

Inamori Yuhei ◽

Kazuo Matsushige ◽

Ryuichi Sudo

Keyword(s):

Nitrogen Removal ◽

Landfill Leachate ◽

Removal Rate ◽

High Strength ◽

Anaerobic Treatment ◽

Combination Method ◽

Surface Loading ◽

Rotating Biological Contactor ◽

Volumetric Loading ◽

Aerobic And Anaerobic

In order to remove high-strength nitrogen and organics in landfill leachate simultaneously, the modified RBC which was combined with the standard RBC and the anaerobic biofilter was proposed. The treatability for actual landfill leachate of the standard RBC and the modified RBC was evaluated. The capability of COD removal in the modified RBC is much greater than that in the standard RBC, although both RBCs showed a BOD removal rate of more than 95%. This suggested that the combination method of aerobic and anaerobic treatment was effective in reducing refractory organic compounds. The nitrogen removal in the modified RBC was about 90% compared to 50% in Che standard RBC. The modified RBC had the advantage of nitrogen removal because nitrification and denitrification proceeded efficiently, even if a carbon source was not added. The performance of the modified RBC was superior to that of the standard RBC in both BOD surface loading and BOD volumetric loading.

Download Full-text