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PubMed1999

Microbial populations, ammonification and nitrification in soil treated with urea and inorganic salts.

Soil fertilization with urea at rates of 0.2 and 0.5 mg N/g soil was toxic for total counts of bacteria and fungi except with cellulolytic fungi where growth was promoted by addition of urea after 90-d incubation. Also, the population numbers of both bacteria and fungi were significantly decreased when soil was amended with CaCl2 and K2SO4 applied at two levels (50 and 100 mumol/g soil). Some alleviation of the toxic effect of either urea or the inorganic salts was observed when they were applied in combination. Fungal species composition was found to be affected in the treated soil. The most tolerant fungi were Alternaria alternata, Aspergillus flavus, A. fumigatus, A. niger, A. terreus, Eurotium amstelodami, E. chevalieri, Nectria haematococca, Paecilomyces variotii and Stachybotrys chartarum. Other species of fungi were either sensitive to all treatments or sensitive to some and tolerant to others. Ammonium nitrogen was found to be more accumulated in soil treated with urea mixed with inorganic salts compared with soil treated only with urea whereas NO3(-)-N (and NO2(-)-N) was decreased. The overall effect of the addition of inorganic salts on total mineralized nitrogen, however was promotive. Soil pH was increased in urea-treated soil but was depressed by application of CaCl2 or K2SO4 to values lower than that of untreated soil. The results may be of agronomical interest in overcoming problems encountered with urea application as N fertilizer.

Ammonia↗
PubMed2006

A strain of Pseudomonas sp. isolated from piggery wastewater treatment systems with heterotrophic nitrification capability in Taiwan.

A high concentration of NH(4) (+) in piggery wastewater is major problem in Taiwan. Therefore, in our study, we isolated native heterotrophic nitrifiers for piggery wastewater treatment. Heterotrophic nitrifier AS-1 was isolated and characterized from the activated sludge of a piggery wastewater system. Sets of triplicate crimp-sealed serum bottles were used to demonstrate the heterotrophic nitrifying capability of strain AS-1 in an incubator at 30 degrees C. All serum bottles contained 80 mL medium, and the remainder of the bottle headspace was filled with pure oxygen. The experimental results showed that 2.5 +/- 0.2 mmol L(-1) NH(4) (+) was removed by 58 hours, and, eventually, 1.5 +/- 0.5 mmol L(-1) N(2) and 0.2 +/- 0.0 mmol L(-1) N(2)O were produced. The removal rate of NH(4) (+) by the strain AS-1 was 1.75 mmol NH(4) (+) g cell(-1) h(-1). This strain was then identified as Pseudomonas alcaligenes (97% identity) by sequencing its 16S rDNA and comparing it with other microorganisms. Thus, strain AS-1 displays high promise for future application for in situ NH(4) (+) removal from piggery wastewater.

Aerobiosis↗
PubMed2005

Nitrification in a vertically moving biofilm system.

A laboratory continuous feed biofilm reactor, comprising a bulk fluid reactor, a biofilm plastic module, a feed tank, and pneumatic devices and controls, was operated for a total period of 257 days, including seeding time, to treat domestic-strength synthetic wastewater under increasing ammonium nitrogen (NH(4)(+)--N) loading rates, ranging from 0.17+/-0.01 (0.71+/-0.06 gm(-2)d(-1)) to 0.70+/-0.02 kgm(-3)d(-1) (2.9+/-0.1 gm(-2)d(-1)). The biofilm plastic module was moved vertically in and out of the wastewater in continuous cycles. The maximum NH(4)(+)-N removal rate was reached during the maximum loading phase, when a NH(4)(+)--N loading rate of 0.70+/-0.02 kgm(-3)d(-1) (2.9+/-0.1 gm(-2)d(-1)) was applied to the system. During this loading period, the average NH(4)(+)--N removal rate was 0.30+/-0.10 kgm(-3)d(-1) (1.30+/-0.40 gm(-2)d(-1)).

Ammonium Chloride↗
PubMed2005

Anaerobic treatment of sludge from a nitrification-denitrification landfill leachate plant.

The viability of anaerobic digestion of sludge from a MSW landfill leachate treatment plant, with COD values ranging between 15,000 and 19,400mg O(2)dm(-3), in an upflow anaerobic sludge blanket reactor was studied. The reactor employed had a useful capacity of 9l, operating at mesophilic temperature. Start-up of the reactor was carried out in different steps, beginning with diluted sludge and progressively increasing the amount of sludge fed into the reactor. The study was carried out over a period of 7 months. Different amounts of methanol were added to the feed, ranging between 6.75 and 1cm(3)dm(-3) of feed in order to favour the growth of methanogenic flora. The achieved biodegradation of the sludge using an upflow anaerobic sludge blanket Reactor was very high for an HRT of 9 days, obtaining decreases in COD of 84-87% by the end of the process. Purging of the digested sludge represented approximately 16% of the volume of the treated sludge.

Anaerobiosis↗
PubMed2006

Nitrogen removal from recycled landfill leachate by ex situ nitrification and in situ denitrification.

A three-compartment system, comprising a landfill column with fresh municipal solid waste, a column with a well-decomposed refuse layer as methane producer, and a sequential batch reactor as ex situ nitrifying reactor, was employed to remove nitrogen from municipal solid waste leachate. Since food waste comprised a major portion of refuse collected in Shanghai, an intense hydrolysis reaction occurred and caused the rapid accumulation of ammonia nitrogen (NH(3)-N) and total organic carbon in the leachate. This paper discusses the role of the three mentioned units and the design and operation of the proposed system. With most NH(3)-N being converted to nitrite nitrogen (NO(2)(-)-N) or nitrate nitrogen (NO(3)(-)-N) by the nitrifying reactor, and with the well-decomposed refuse layer transforming most dissolved organic compounds to CO(2), carbonates and methane, it was found that the fresh refuse column could efficiently denitrify the hydrolyzed nitrogen to N(2) gas. The role of the three mentioned units and comments on the design and operation of the proposed system are also discussed.

Ammonia↗
PubMed2005

Oxygen-limited autotrophic nitrification-denitrification (OLAND) in a rotating biological contactor treating high-salinity wastewater.

A lab-scale rotating biological contactor (RBC) reactor operated under OLAND conditions was slowly adapted during 178 days to increasing salt concentrations going up to 30 g NaCl L(-1). The reactor performed well during this experimental period. However, the removal capacity of the reactor was lower under high-salinity conditions. A removal efficiency of 84% was achieved at a N loading rate of 725 mg N L(-1) d(-1) and a salt concentration of 30 g L(-1). The effect of salt shock loading and adaptation to 30 g NaCl L(-1) on the specific nitritation and anammox activity of the biomass was investigated in short-term batch experiments. A salt shock loading of 30 g L(-1) caused a 43% decrease in specific nitritation activity and 96% loss of specific anammox activity compared to reference biomass (not exposed to salt). The salt-adapted biomass (3-4 weeks) showed a specific nitritation activity that was 23% lower, and a specific anammox activity that was 58% lower, compared to the reference biomass. Overall, these results demonstrate that the OLAND process can have the potential to treat ammonium-rich brines after adaptation to high salinity.

Biodegradation, Environmental↗