[Investigation of nitrogen removal efficiency from wastewater using modified anaerobic baffled reactor [MABR]]

Nitrogen compounds in wastewater are mainly in four types of organic, ammonia, nitrite and nitrate. Total nitrogen concentration in municipal wastewater is usually within 25 to 45 mg/L as nitrogen. The most important problem with nitrogen is its oxygen demand and human health effect. Anaerobic Baffled Reactor [ABR] is a system in which baffles are used to direct wastewater flow. During 9 months study, a 15 liter modified ABR [104*30*15 cm] with eight baffled compartments was used for nitrification-denitrification processes. In the seventh compartment, the wastewater was aerated to oxidize ammonia to nitrite and nitrate. Denitrification was done in the first four compartments with removal efficiency from 60 to 84 percent for nitrite and nitrate, respectively. During the shock loading study [4 times of the last influent], a sharp decrease in nitrogen removal rate was observed which was then returned to the previous efficiency after 11 days. Artificial neural network was used to evaluate and process the data in which the observed error in 10 patterns was less than 15 percent. Anaerobic baffled reactor with an influent of up to 200 mg/L has capability to remove total nitrogen concentration to less than the standard level of Iranian Department of Environment of 50 mg/L as nitrate and 10 mg/L as nitrogen

Metabolismos microbianos involucrados en procesos avanzados para la remoción de nitrógeno, una revisión prospectiva / Microbial metabolisms over advanced processes for nitrogen removal, a prospective review

Los procesos avanzados para la remoción de nitrógeno están íntimamente relacionados con los metabolismos de las comunidades microbianas que intervienen en las transformaciones del mismo. Para el diseño, la optimización o el mejoramiento de los sistemas de tratamiento de aguas residuales domésticas, el ingeniero y el microbiólogo en forma conjunta, han logrado configurar reactores terciarios adecuados para el desenvolvimiento de estas comunidades, obteniendo altas eficiencias de remoción de los nutrientes. Este artículo presenta una revisión sobre la actividad bacteriana y su aplicación en los sistemas de tratamiento, inicia conceptualizando la influencia de los microorganismos y de la actividad humana en el ciclo global del nitrógeno, para después hacer un análisis de los procesos particulares en los cuales los microorganismos intervienen. Se clasifican e incluyen nuevas evidencias de metabolismos relacionados, y se describen como ejemplos algunos de los procesos de tratamiento terciario para aguas residuales desarrollados con éxito en las últimas décadas.

Advanced processes for nitrogen removal are intimately related to the microbial community metabolisms that take part in the transformations. For the design, optimization or improvement of domestic waste water treatment systems, engineers and microbiologists working together, have managed to implemented suitable tertiary reactors for the development of these communities, improving the efficiency of nutrient removal. This article presents a revision of the bacterial activity and its application in treatment systems. The article begins by giving an explanation about the influence of microorganism and human activity on the global nitrogen cycle. Then, it analyzes the particular processes in which the microorganisms take part. New evidence of related metabolisms are classified and included. Some of the processes of wastewater tertiary treatment, successfully developed over the last decades, are described as examples.

Treatment of polluted river water by a gravel contact oxidation system constructed under riverbed

The objective of this study was to evaluate the treatment efficiency of a gravel contact oxidation treatment system which was newly constructed under the riverbed of Nan-men Stream located at the Shin Chu City of Taiwan. The influent and effluent water samples were taken periodically for the analyses of pH, temperature, dissolved oxygen, total suspended solids, five-day biological oxygen demand, NH4[+]-N. The results showed that the average removal rates of five-day biological oxygen demand, total suspended solids and NH4[+]-N were 33.6% [between -6.7% and 82.1%], 56.3% [between -83.0% and 93.4%] and 10.7% [between -13.0% and 83.3%], respectively. The calculated mean first order reaction rate constant for five-day biological oxygen demand was 4.58/day with a standard deviation of 4.07/day and for NH4[+]-N was 2.15/day with a standard deviation of 5.68/day. Therefore, it could be said that this gravel-contact-oxidation system could effectively remove biological oxygen demand, total suspended solids, and NH4[+]-N in river water at a relatively short hydraulic retention time, although its pollutant treatment efficiency was not quite stable. However, to reach better or more stable treatment efficiency, aeration might sometimes be necessary to increase the dissolved oxygen in influent river water. And, longer hydraulic retention time of the system might also be required to increase NH4[+]-N removal efficiency

Performance of Spodoptera litura Fabricius on different host plants: influence of nitrogen and total phenolics of plants and mid-gut esterase activity of the insect.

Five host plants [castor, Ricinus communis (Carolus Linnaeus); cotton, Gossypium hirsutm (Carolus Linnaeus); tomato, Lycopersicum esculentum (Philip Miller); mint, Mentha arvensis (Carolus Linnaeus) and cabbage, Brassica oleracea (Carolus Linnaeus)] belonging to different families were used to study the performance of the Asian armyworm, Spodoptera litura larvae. Highest consumption of food and dry weight gain was observed in larvae fed on castor. Mint did not support optimum larval growth because of low digestibility and low efficiency of conversion of digested food to body matter. Dry weight gain ranged from 26.64 mg on mint to 86.80 mg in castor. These differences tend to be related to nitrogen and total phenolics content of the leaf tissues; however, the most clear-cut correlation is an inverse one between the host plant preference and the ratio of total phenolics to nitrogen in the leaf tissues. Mid-gut esterase activity in larvae showed an increasing trend with the increase in total phenolics: nitrogen ratio in the test plants and the order of mid-gut esterase activity in larvae was mint > cabbage > cotton > tomato > castor.

The interactive effect of phosphorus and nitrogen on "In vitro" spore germination of glomus etunicatum Becker & Gerdemann, root growth and mycorrhizal colonization

The effects of P and N amendment and its interactions on spore germination, root growth and colonized root length by Glomus etunicatum Becker & Gerdemann (INVAM S329) was studied "in vitro"in RiT-DNA transformed roots of Anthylis vulneraria sub sp. Sampaiana (Kidney vetch). Three N media concentrations (5, 10 and 50 mg/l) at P constant level (2 mg/l) and three P media concentrations (2, 10 and 20 mg/l) at N constant level (5 mg/l) were utilized as a treatment. Bécard & Fortin medium was used as a basal medium for root growth and colonized root length, and water/agar 0.8(per cent) media was the control for spore germination. Spore germination of G. etunicatum at low P level was reduced by N addition in relation to the control media, and at low N level addition of P stimulated spore germination. Total root length was stimulated by N addtion at low P level, but no significant difference (p<0.05) was observed among P concentrations. Colonized root lenght by G. etunicatum increased significantly (pz0,05) with P additions at low N levels. Under low P level no significant differences was found between 10 and 50 mg/l of N. These results demonstrate that the interaction between P and N affect differently spore germination, root growth and colonized root lenght.