Propionate-cultured sludge bioaugmentation to enhance methane production and micropollutant degradation in landfill leachate treatment.

This research investigates the use of propionate-cultured sludge to enhance methane (CH4) production and micropollutant biodegradation in biochemical methane potential (BMP) experiment treating landfill leachate. The experiments were carried out using non-acclimatized and acclimatized seed sludge with variable food to microorganism ratios of 1:1 and 1:2. Under the propionate-cultured sludge bioaugmentation, the concentrations of propionate-cultured sludge were varied between 10, 20, and 30 % (v/v). The acclimatized seed sludge exhibited high microbial abundance and diversity which promoted the CH4 production and micropollutant biodegradation. The modified Gompertz model indicated that the optimal condition was the acclimatized seed sludge with 30% (v/v) propionate-cultured sludge, achieving the lag time (λ), maximum CH4 production rate (Rmax), and maximum CH4 potential yield (Pmax) of 0.57 day, 17.35 NmL/h, and 140.58 NmL/g COD. The research novelty lies in the use of propionate-cultured sludge bioaugmentation in landfill leachate treatment to enhance CH4 production and micropollutant biodegradation.

Effect of leachate effluent from activated sludge and membrane bioreactor systems with acclimatized sludge on plant seed germination.

This research comparatively investigates the effect of landfill leachate effluent of two biological treatment schemes on germination of Lactuca sativa and Vigna radiata. The treatment schemes are two-stage activated sludge (AS) and two-stage membrane bioreactor (MBR) systems with acclimatized seed sludge. The AS and MBR are operated under two concentrations of landfill leachate influent: moderate (condition 1) and elevated (condition 2). The results show that, under condition 1, the AS and MBR efficiently remove 80-96% of organic compounds and nutrients and 81-100% of harmful micropollutants. Under condition 2 with elevated influent concentration, MBR is more effective in biodegrading micropollutants than the AS system. The germination rate (GR) and germination seed index (GSI) of L. sativa and V. radiata germinated with AS and MBR effluent from condition 1 are 100% and 1.29-1.56. Under condition 2, the GR and GSI with AS effluent are reduced to 80% and 0.65-0.77, while those with MBR effluent are 100% and 1.27-1.38. Quantitative real-time polymerase chain reaction (qPCR) analysis indicates that the bacterial community in the MBR is more abundant than in the AS, especially ammonia oxidizing bacteria, Nitrobacter, and Nitrospira, which aid heterotrophic bacteria in biodegradation of micropollutants and promote the growth of heterotrophs. The bacterial abundance and community composition render the MBR scheme more operationally suitable for elevated landfill-leachate influent concentrations. By comparison, the MBR system is more effective in removal of micropollutants than the AS, as evidenced by higher GR and GSI. The technology also could potentially be applied to water reclamation. A lack of technological and financial resources in many developing countries nevertheless precludes the adoption of MBR despite higher pollutant removal efficiency. An alternative solution is the use of acclimatized seed sludge in AS system to enhance treatment efficiency, especially in influent with low concentrations of micropollutants. In addition, the seed germination results suggest the possibility of water reuse in agriculture.

Inhibition of anaerobic ammonium oxidation (anammox) bacteria by addition of high and low concentrations of chloramphenicol and comparison of attached- and suspended-growth.

Inhibition of anammox activities was tested with two ranges of chloramphenicol (CAP) concentration (5, 10, 20, 50, and 100 mg L-1) and (100, 500, and 1000 µg L-1). In a short-term study, strong inhibition of activity was dependent of CAP concentration in both attached-growth (SBR-A) and suspended-growth (SBR-S) systems. The activities of attached-growth cultures at all CAP concentrations were reversible after 1 day, while activities for suspended-growth cultures were only gradually reversible dependent on the CAP concentrations. In long-term studies with daily additions of 6 mg L-1 CAP, the anammox activity on day 41 in SBR-A had decreased to 18% baseline (SAA reduced from 0.528 to 0.096 mg N mg-1 VSS d-1). More rapid reduction of anammox activity was observed in SBR-S, down to 17% baseline after only 27 days (SAA decreased from 0.576 to 0.096 mg N mg-1 VSS d-1). Inhibition was irreversible in both SBR-S and SBR-A after the long-term study. With lower CAP additions (100-1000 µg L-1), the activities in both reactors were stable during daily CAP addition for two weeks. Attached-growth cultures tended to be more tolerant of CAP addition than suspended-growth cultures. Both un-competitive and non-competitive models could be used to compare anammox activities with the higher CAP concentrations. The SAAmax [fx] (the maximum specific anammox activity) and hKi (the inhibition constant) of SBR-A were 0.48 mg N mg-1 VSS d-1 and 98.3 mg L-1, respectively. The SAAmax[fx] and Ki of SBR-S were 1.25 mg N mg-1 VSS d-1and 71.1 mg L-1, respectively.

Enhanced micropollutant biodegradation and assessment of nitrous oxide concentration reduction in wastewater treated by acclimatized sludge bioaugmentation.

This research investigated the micropollutant biodegradation and nitrous oxide (N2O) concentration reduction in high strength wastewater treated by two-stage activated sludge (AS) systems with (bioaugmented) and without (non-bioaugmented) acclimatized sludge bioaugmentation. The bioaugmented and non-bioaugmented systems were operated in parallel for 228 days, with three levels of concentrations of organics, nitrogen, and micropollutants in the influent: conditions 1 (low), 2 (moderate), and 3 (high). The results showed that, under condition 1, both systems efficiently removed the organic and nitrogen compounds. However, the bioaugmented system was more effective in the micropollutant biodegradation and N2O concentration reduction than the non-bioaugmented one. Under condition 2, the nitrogen and micropollutant biodegradation efficiency of the non-bioaugmented system slightly decreased, while the N2O concentration declined in the bioaugmented system. Under condition 3, the treatment performance and N2O concentration abatement were substantially lowered as the compounds concentration increased. Further analysis also showed that the acclimatized sludge bioaugmentation increased the bacterial diversity in the system. In essence, the acclimatized sludge bioaugmentation strategy was highly effective for the influent with low compounds concentration, achieving the organics and nitrogen removal efficiencies of 92-97%, relative to 71-97% of the non-bioaugmented system. The micropollutant treatment efficiency of the bioaugmented system under condition 1 was 75-92%, indicating significant improvement in the treatment performance (p < 0.05), compared with 60-79% of the non-bioaugmented system.

Toxic compounds biodegradation and toxicity of high strength wastewater treated under elevated nitrogen concentration in the activated sludge and membrane bioreactor systems.

This research has assessed the removal efficiencies of toxic compounds in the high strength wastewater (the leachate and agriculture wastewater mixture) using the activated sludge (AS) and membrane bioreactor (MBR) technologies under two carbon to nitrogen (C/N) ratios (C/N 14 and 6) and two toxic compounds concentrations (8-396µg/L and 1000µg/L). In addition, the toxicity evaluations of the AS and MBR effluents to the aquatic environment were undertaken at five effluent dilution ratios (10, 20, 30, 50 and 70% v/v). The findings indicate that the AS treatment performance could be enhanced by the elevation of the nitrogen concentration. Specifically, the C/N 6 environment helps promote the bacterial growth, particularly heterotrophic nitrifying bacteria (HNB) and nitrifying bacteria (NB), which produce the enzymes crucial to the toxic compounds degradation. The improved biodegradation makes the effluents less toxic to the aquatic environment, as evidenced by the lower mortality rates of both experimental fish species raised in the nitrogen-elevated diluted AS effluents. On the other hand, the elevated nitrogen concentration minimally enhances the MBR treatment performance, given the fact that the MBR technology is in itself a biological treatment scheme with very high compounds removal capability. Despite its lower toxic compounds removal efficiency, the AS technology is simple, inexpensive and operationally-friendly, rendering the system more applicable to the treatment operation constrained by the financial, manpower and technological considerations.

Resuscitation of starved suspended- and attached-growth anaerobic ammonium oxidizing bacteria with and without acetate.

Anammox application for nutrient removal from wastewater is increasing, though questions remain about anammox resilience to fluctuating conditions. Resuscitation of anammox suspended- and attached-growth cultures after 3 months of starvation was studied with and without acetate dosing. Without acetate, the attached-growth culture recovered more quickly than the suspended-growth culture. Suspended-growth cultures recovered more quickly (within 60 days) with weekly and daily acetate dosing than without, but anammox activity and copy numbers decreased with continued acetate addition. All attached-growth cultures recovered within 60 days, but after that activity with acetate dosing was consistently at least 20% lower than that without acetate addition. Ca. Jettenia caeni, Ca. Anammoxoglobus sp., Ca. Brocadia fulgida, Ca. Brocadia anammoxidans, Ca. Brocadia fulgida and Ca. Jettenia asiatica were identified. Acetate addition can significantly accelerate short-term resuscitation of enriched anammox suspended-growth cultures after starvation but may reduce anammox activity over the longer term in suspended- and attached-growth cultures.