Impact of organic loading rates on the clogging dynamics in the tower-hybrid macrophyte-assisted vermifilters

This research evaluates the effect of both organic and ammonia loading rates and the presence of plants on the removal of chemical oxygen demand and ammonia nitrogen in horizontal subsurface flow constructed wetlands, 2 years after the start-up. Two sets of experiments were carried out in two mesocosms at different organic and ammonia loading rates (the loads were doubled); one without plants (control bed), the other colonized with Phragmites australis. Regardless of the organic loading rate, the organic mass removal rate was improved in the presence of plants (93.4 % higher for the lower loading rate, and 56 % higher for the higher loading rate). Similar results were observed for the ammonia mass removal rate (117 % higher for the lower loading rate, and 61.3 % higher for the higher loading rate). A significant linear relationship was observed between the organic loading rate and the respective removal rates in both beds for loads between 10 and 13 g m−2 day−1. The presence of plants markedly increase removal of organic matter and ammonia, as a result of the role of roots and rhizomes in providing oxygen for aerobic removal pathways, a higher surface area for the adhesion and development of biofilm and nitrogen uptake by roots.

Four microbial fuel cells (MFCs) inoculated with different bacterial species were constructed. The species were Pseudomonas putida, Comamonas testosteroni, Corynebacterium gultamicum, and Arthrobacter polychromogenes. The MFCs were operated under identical continuous flow conditions. The factors affecting the capabilities of the MFCs for treating organic matter and generating power were evaluated and compared. The factors include microbial species type, organic loading, and substrate degradation rate. For all four MFCs, power output increased with the organic loading rate. Power density also increased with the substrate degradation rate. These findings implied that more organic matter was utilized for power generation at higher organic loading and substrate degradation rates. However, coulombic efficiency increased with decreased organic loading and substrate degradation rates. Apparently, all four MFCs had low efficiencies in generating power from organic matter. These low efficiencies are attributed to the long distance between the anode and the cathode, as well as to the small ratio of the proton exchange membrane surface area to the anode chamber surface area. These features may have caused most of the protons produced in the anode chamber to leave the chamber with the effluent, which led to the low power generation performance of the MFCs.

A laboratory‐scale anaerobic down‐flow fixed‐bed reactor, operating at 35°C, was used to treat abattoir wastewater at input soluble chemical oxygen demand (COD) levels ranging from 4·7 to 28·7 g sm−3 and volumetric organic loading rates ranging from 2·5 to 25 g COD dm −3 day −1. Start up of the reactor was achieved within 35 days using a regime that include stepped increases in input COD and methanol substitution. The effects of the organic volumetric loading rates on soluble (COD) (SCOD) removal were studied at four feed SCOD concentrations between 4·7 and 28‐7 g dm−3. An exponential dependency of the organic volumetric loading rate with the SCOD removal was observed in the range of loading studied, with variation between 1 and 12 g COD sm−3 day −1 Further increases of the organic loading rates has smaller effects on SCOD removal. A pseudo first‐order kinetic model was used to obtain the gross removal coefficients, the values of which were virtually independent of the feed COD concentration at 6·9 to 7·3 g COD dm −3 day −1. The methane yield coefficient decreased slightly from 0·34 to 0·31 dm 3 g −1 COD when the feed SCOD concentration was increased from 4·7 to 28·7 g dm −3.

Neste trabalho, objetivou-se efetuar a avaliação operacional de três filtros anaeróbios com fluxo ascendente, utilizados no tratamento da água residuária do processamento dos frutos do cafeeiro (ARC). Os filtros, confeccionados com tubos PVC, preenchidos com brita nº 2 e com volume total de 139,5 L, foram operados sob temperatura ambiente, que variou de 13,8 a 24,4 ºC. A ARC teve o pH corrigido com cal até valores próximos a 7. A concentração de nutrientes foi corrigida mantendo-se relação DBO/N/P igual a 100/5/1. A carga orgânica volumétrica e o tempo de residência hidráulica variaram de 1,49 a 12,99 kg m-3 d-1 e de 32,3 a 56,9 h, respectivamente. O monitoramento foi realizado com a coleta de amostras afluentes e efluentes dos filtros, quantificando-se as variáveis DQO, DBO, compostos fenólicos, pH, alcalinidade e ácidos voláteis. Como resultado, observou-se que a grande oscilação na carga hidráulica e orgânica fez com que os filtros anaeróbios, utilizados neste trabalho, operassem de forma instável, apresentando desequilíbrio entre os micro-organismos produtores e consumidores de ácidos voláteis, com produção não satisfatória de alcalinidade na forma de bicarbonato. No entanto, os valores de pH afluente e efluente mantiveram-se dentro da faixa de valores adequados para que ocorresse a degradação anaeróbia do material orgânico. Os filtros não suportaram o choque de carga orgânica, o que reduziu drasticamente a eficiência de remoção de matéria orgânica e de compostos fenólicos. Com base na análise de desempenho e nas condições operacionais empregadas, a carga orgânica máxima a ser aplicada em filtros anaeróbios para tratamento de ARC, não deve exceder 2 kg m-3 d-1 de DQO.

The performance of an aerated submerged fixed-film reactor (ASFFR) under simultaneous organic and ammonium loading and its effect on nitrification was studied. Organic loadings varied in the range of 1.93 to 5.29 g chemical oxygen demand (COD) m-2 d-1 and NH4-N loadings were in the range of 116 to 318 mg NH4-N m-2 d-1. Increments of loading rates were obtained both by increasing the flow rate and increasing the influent substrate in individual pilot runs. Results showed that with organic loading rates up to 3.97 g COD m-2 d-1, complete nitrification was achievable. Although high organic loading such as 5.29 g COD m-2 d-1 could cause nitrification to stop, shifting to lower organic loadings made nitrification start and set rapidly to its previous steady-state concentrations. Comparison of results showed that in the ASFFR, nitrification would be severely affected by an organic loading rate of 5.29 g COD m-2 d-1 by increasing either the flow or the influent substrate. It should be noted that the average value of dissolved oxygen was 3.4 mg L-1 with an air supply of 15 L min-1, and there was no indication of oxygen limitation. The results of this study show the flexibility of ASFFRs under changing organic loads. Furthermore, for achieving complete nitrification and optimum application of these reactors for protecting receiving water from the environmental hazards of ammonium, the maximum organic loading that would present complete nitrification should be considered.

The upflow anaerobic sludge blanket (UASB) has been used successfully to treat a variety of industrial wastewaters. It offers a high degree of organics removal, low sludge production and low energy consumption, along with energy production in the form of biogas. However, two major drawbacks are its long start‐up period and deficiency of active biogranules for proper functioning of the process. In this study, the influence of a coagulant polymer on start‐up, sludge granulation and the associated reactor performance was evaluated in four laboratory‐scale UASB reactors. A control reactor (R1) was operated without added polymer, while the other three reactors, designated R2, R3 and R4, were operated with polymer concentrations of 5 mg dm−3, 10 mg dm−3 and 20 mg dm−3, respectively. Adding the polymer at a concentration of 20 mg dm−3 markedly reduced the start‐up time. The time required to reach stable treatment at an organic loading rate (OLR) of 4.8 g COD dm−3 d−1 was reduced by more than 36% (R4) as compared with both R1 and R3, and by 46% as compared with R2. R4 was able to handle an OLR of 16 g COD dm−3 d−1 after 93 days of operation, while R1, R2 and R3 achieved the same loading rate only after 116, 116 and 109 days respectively. Compared with the control reactor, the start‐up time of R4 was shortened by about 20% at this OLR. Granule characterization indicated that the granules developed in R4 with 20 mg dm−3 polymer exhibited the best settleability and methanogenic activity at all OLRs. The organic loading capacities of the reactors were also increased by the addition of polymer. The maximum organic loading of the control reactor (R1) without added polymer was 19.2 g COD dm−3 d−1, while the three polymer‐assisted reactors attained a marked increase in organic loading of 25.6 g COD dm−3 d−1. Adding the cationic polymer could result in shortening of start‐up time and enhancement of granulation, which may in turn lead to improvement in the efficiency of organics removal and loading capacity of the UASB system. Copyright © 2004 Society of Chemical Industry

Accelerated start-up and enhanced granulation in upflow anaerobic sludge blanket reactors

Accelerated start-up and enhanced granulation in upflow anaerobic sludge blanket reactors

This study investigated the impact of intermittent aeration strategies and reduction in the reactor’s organic and nitrogen loading rates on the course of particular stages of the nitrification process, as well as energy consumption and N2O emissions in a hybrid reactor with nitrification/denitrification. Each of the analysed series revealed the greatest ammonia oxidation activity in activated sludge flocs. The highest activity of nitrite nitrogen oxidation was demonstrated in the case of biofilm. A reduction in the reactor’s organic and nitrogen loading rate value had a greater effect on changes in the activity of ammonia-oxidizing bacteria than nitrite-oxidizing bacteria. In a system where the operation of air pumps was controlled through switching them and off according to the adopted ratio between non-aerated and aerated sub-phase times and the assumed oxygen concentration, a reduction in the duration of aerated sub-phases caused no decrease in energy use for aeration. Lower N2O emission was recorded when the reactor operated with a longer duration of aerated sub-phases.

Psychrophilic and mesophilic anaerobic digestion of brewery effluent: A comparative study

Microalgal-based systems for wastewater treatment: Effect of applied organic and nutrient loading rate on biomass composition

Influence of organic loading and aeration rates on performance of a lab-scale upflow aerated submerged fixed-film bioreactor

Biohydrogen production in a granular activated carbon anaerobic fluidized bed reactor

Treatment of low strength industrial cluster wastewater by anaerobic hybrid reactor

The discharge of industrial effluent constituting high orthophosphates and organic pollutants in water receiving bodies compromises freshwater quality and perpetuates eutrophication. In this study, an anaerobic–aerobic sequencing batch reactor (SBR) under activated sludge was investigated for orthophosphates and chemical oxygen demand (COD) removal from brewery wastewater. Raw brewery wastewater samples were collected on a daily basis for a period of 4 weeks. The findings of the study are reported based on overall removal efficiencies recording 69% for orthophosphates and 54% for total COD for a sludge retention time (SRT) of 7 days and hydraulic retention time of 18 h at mesophilic temperature conditions of ±25 °C. Moreover, the SBR system showed stability on orthophosphate removal at a SRT ranging from 3 to 7 days with a variation in organic volumetric loading rate ranging from 1.14 to 4.83 kg COD/m3.day. The anaerobic reaction period was experimentally found to be 4 h with the aerobic phase lasting for 14 h. The SBR system demonstrated feasibility on orthophosphates and COD removal with variation in organic loading rate.