Microbial interactions and nitrogen removal performance in an intermittently rotating biological contactor treating mature landfill leachate.

Developing efficient landfill leachate treatment is still necessary to reduce environmental risks. However, nitrogen removal in biological treatment systems is often poor or costly. Studying biofilms in anoxic/aerobic zones of rotating biological contactors (RBC) can elucidate how microbial interactions confer resistance to shock loads and toxic substances in leachate treatment. This study assessed the nitritation-anammox performance in an intermittent-rotating bench-scale RBC treating mature leachate (diluted). Despite the leachate toxicity, the system achieved nitritation with an efficiency of up to 34 % under DO values between 0.8 and 1.8 mg.L-1. The highest average ammoniacal nitrogen removal was 45.3 % with 10 h of HRT. The 16S rRNA sequencing confirmed the presence of Nitrosonomas, Aquamicrobium, Gemmata, and Plantomyces. The coexistence of these bacteria corroborated the selective pressure exerted by leachate in the community structure. The microbial interactions found here highlight the potential application of RBC to remove nitrogen in landfill leachate treatment.

Effects of temperature, proportion and organic loading rate on the performance of anaerobic digestion of food waste.

In Brazil, a significant amount of organic waste is produced in households and restaurants. This study thus aimed to determine the ideal conditions for generating methane from the treatment of household waste by anaerobic digestion, under mesophilic (37 °C) and thermophilic (55 °C) conditions, to determine the maximum organic loading rate (OLR) in the reactors, and to evaluate kinetic parameters by statistical models: Modified Gompertz, First-Order, Logistic and Transference functions. The experiments were conducted in anaerobic batch reactors. Different proportions of pre-prepared waste (PPW)/leftover waste (LW) were used: 100/0, 75/25, 50/50, 25/75, and 0/100 and different ORL: 0.15; 0.30; 0.45; 0.60; and 0.90 g TVS (Total Volatile Solids).L-1.d-1. For both conditions, the optimal proportions of PPW/LW were 100/0 and 75/25 %. Under mesophilic condition, the best results were observed (869 mL of CH4.g TVS-1). The maximum organic load was 0.30 g TVS.L-1.d-1. The best data adjustment was performed by the Transference function.

Intermittent rotation as an innovative strategy for achieving nitritation in rotating biological contactors.

The nitritation step is essential when the anammox process is focused, and alternative technologies to achieve partial nitritation-anammox are required. Rotating Biological Contactors (RBCs) are a promising and cost-effective technology, allowing the development of aerobic and anoxic zones in the biofilm, coupled to low energy consumption. This study evaluated nitritation in a RBC with two discs rotation strategies: continuous and intermittent. Continuous rotation resulted in high dissolved oxygen (DO) concentrations and was not favorable for achieving stable nitritation. However, intermittent rotation, coupled with a nitrogen load of 1000 g N·m-3·d-1 and a HRT of 12 h, decreased DO by 77.8% and resulted in nitritation efficiencies of 45.3%. FISH analyses suggested that simultaneous partial nitritation/anammox (PN/A) could also be favored. These results indicated that intermittent rotation may be a core strategy for producing an anammox-suitable effluent or even to promote PN/A in RBCs, upgrading their applicability for wastewater treatment.

Ammonia removal and recovery from municipal landfill leachates by heating.

In this research, ammonia evaporation capacity under atmospheric and vacuum pressure conditions, as well as distillation capacity of different concentrations of landfill leachates, were evaluated. Simple evaporation and vacuum pressure evaporation tests showed high NH3-N removal efficiencies, ranging from 95% to 98% for raw landfill leachates, indicating that vacuum pressure would not be necessary during ammonia removal and recovery processes when applying temperature of 300 °C. Distillations tests also showed the promising NH3-N recovery potential in ultra-concentrated leachates (over 100 gNH3-N/L) in the order of 91%-94% in few minutes, evaporating a small portion of landfill leachate. The results presented encourages the recovery of ammonia from landfill leachate and its industrial and agricultural, highlighting its feasibility as well as simultaneously preventing the ammonia release to water bodies or the atmosphere.

Phosphorus recovery from sewage with a sustainable and low-cost treatment system.

This study proposes a technology conceived based on an integrative approach that aims to promote phosphorus recovery and to recycle ferric water treatment sludge (FWTS), using it as a phosphorus adsorbent which may be applied as a soil ameliorant after reaching saturation. The assessed pilot plant operated with a daily influent flow of 360 litres and presented a removal efficiency of 94.4% ± 3.2% for chemical oxygen demand (COD) and of 91.2% ± 7.8% for suspended solids. It also presented promising results for phosphorus removal. The maximum efficiency of dissolved reactive phosphorus removal was 95% on the first day and it decreased until reaching adsorbent saturation. The estimated breakthrough time was one year in the condition in which the filling medium of a second constructed wetland was only FWTS. In this situation, the effluent phosphorus concentration was 0.2 mg·L-1. The authors concluded that the application of FWTS in a constructed wetland bed is an interesting alternative. Batch adsorption experiments were run using phosphorus stock solution. Langmuir and Freundlich adsorption isotherm models were obtained for different initial pH values. The maximum adsorption capacity decreased as the initial pH was increased; values ranged from 4.76 mg P·g-1 (pH = 3.9) to 1.44 mg P·g-1 (pH = 9.0).

Biomass growth and its mobility in an AnSBBR treating landfill leachate.

This work used a pilot scale (with a total volume of 1300 L) Anaerobic Sequencing Batch Biofilm Reactor (AnSBBR) to treat landfill leachate from São Carlos-SP (Brazil) as well as to evaluate the biomass growth and its behavior. Biomass from the bottom of a landfill leachate stabilization pond was immobilized in polyurethane foam cubes as inoculum. The leachate characteristics varied during the experiment. Ethanol or volatile fatty acids were added as additional substrate when the leachate was temporarily recalcitrant. After acclimation, the AnSBBR presented efficiency over 70% (COD removal). A mass balance model, biomass sampling and temporal concentration profiles were performed to obtain a biomass yield coefficient of YX/S = 0.0251 ±â€¯0.0006 gTVS gCOD removed (r2 = 0.999). Additionally, it was observed that a variable fraction of the attached biomass may detach itself or present mobility during the batch time, however returning to fixed bed depending on the substrate type and concentration. This behavior has never been reported by the literature for attached biomass.

First-order kinetics of landfill leachate treatment in a pilot-scale anaerobic sequence batch biofilm reactor.

This paper reports the kinetics evaluation of landfill leachate anaerobic treatment in a pilot-scale Anaerobic Sequence Batch Biofilm Reactor (AnSBBR). The experiment was carried out at room temperature (23.8 ± 2.1 °C) in the landfill area in São Carlos-SP, Brazil. Biomass from the bottom of a local landfill leachate stabilization pond was used as inoculum. After acclimated and utilizing leachate directly from the landfill, the AnSBBR presented efficiency over 70%, in terms of COD removal, with influent COD ranging from 4825 mg L(-1) to 12,330 mg L(-1). To evaluate the kinetics of landfill leachate treatment, temporal profiles of CODFilt. concentration were performed and a first-order kinetics model was adjusted for substrate consumption, obtaining an average k1 = 4.40 × 10(-5) L mgTVS(-1) d(-1), corrected to 25 °C. Considering the temperature variations, a temperature-activity coefficient θ = 1.07 was obtained. Statistical "Randomness" and "F" tests were used to successfully validate the model considered. Thus, the results demonstrate that the first-order kinetic model is adequate to model the anaerobic treatment of the landfill leachate in the AnSBBR.