Background and Objectives: Low nitrogen use efficiency (NUE) is a global problem in crop production, and agriculture of Iran is not exempt in this regard. Nitrogen (N) fertilizers as a source of nitrogen can be very effective in water, soil and air environmental pollution. Nitrification is a key process in agricultural ecosystems since it results in changes of ammonium to nitrate and eventually loss of considerable amounts of soil nitrogen through leaching and denitrification. The application of nitrification inhibitors (NI) together with nitrogen fertilizers is a strategy to reduce N losses. Thus, the objective of this study were to evaluate the effect of inhibitor 3, 4-Dimethylpyrazole phosphate (DMPP) on nitrification rates and nitrification inhibition percentage in some soils of Iran containing representing differences in organic matter content and texture. Materials and Methods: An incubation experiment was conducted to evaluate the effect of DMPP on nitrate and ammonium concentration changes in different times and abundance of ammonium (AOB) and nitrite (NOB) oxidizer bacteria in five soils with different texture and organic carbon (O. C). The treatments of experiment included NI at three levels (without N and NI, 200 mg/kg N as ammonium sulfate without NI and 200 mg/kg N as ammonium sulfate containing 0. 8 % NI), five soil types (sandy loam 1 with 0. 58% O. C, sandy loam 2 with 0. 3% O. C, loam with 0. 73% O. C, clay loam with 0. 87% O. C, clay with 1. 47% O. C), and five sampling times (0, 14, 28, 42, and 56 day). Results: The results showed that application of N containing DMPP compared to N without DMPP in all soils had significant effect (P<0. 001) on reducing nitrification, which was reduced 44. 7% on average. DMPP efficiency on nitrification inhibition in experimented soils had significant difference, indicating that nitrification occurs rapidly in soils containing more clay and O. C compared to soils with more sand and low O. C. Nitrification inhibition percentage after 56 day incubation in SL1, SL2 and L were 57%, 46% and 12%, but in two other soils were about zero. Also there were a positive significant correlation between abundance of AOB and NOB with nitrate concentration (r = 0. 6), O. C content (r = 0. 9) and total soil N (r = 0. 9). Conclusions: Soil nitrification rate are different under influence of factors like soil textural properties and soil O. C content, and DMPP efficiency had inverse relationship with some soil properties including clay%, O. C content and nitrifier bacterial population.

Soil and water pollution and waste of resources have occurred due to the excessive use of nitrogen fertilizers in paddy fields. Considering that the biofilm of periphyton formed in paddy fields is mainly responsible for the exchange of nutrients, the present research was designed to investigate the effect of periphyton in the nitrification process in paddy fields and performed with 12 treatments. The treatments included powerful and weak nitrifiers isolated from periphyton, periphyton, periphyton enriched with nitrifiers, and their combination with a dicyandiamide chemical inhibitor. The research was carried out in a rice greenhouse cultivation for 30 days. The results showed that the simultaneous application of periphyton enriched with low-power nitrifier and dicyandiamide can increase the amount of total soil nitrogen, soil phosphorus, soil ammonium, total plant nitrogen, plant phosphorus, plant potassium, shoot length, and dry weight of rice plants. While this treatment reduced the conversion of ammonium to nitrate and subsequently reduced the potential of nitrate formation in the soil, with the increase of ammonium accumulation, it increased the utilization of rice plants. Periphyton can be considered a source for the isolation of nitrifiers. Also, the use of periphyton in paddy fields as a biological and healthy solution to inhibit the nitrification process in front of the use of inhibiting chemicals is placed in the path of future research.

Nitrogen removal from hypersaline wastewater was successfully started up by inoculating estuarine sediments for 140 days. Efficient ammonia and total nitrogen removal was sustained under specific ammonia loading of 0.016-0.139 kg N/[kg VSS day] in a sequencing batch reactor. Stable nitrite accumulation was observed during nitrification. The specific ammonia consumption rate was higher than the value of freshwater activated sludge and salt-acclimated freshwater activated sludge. With methanol as carbon source, specific nitrite reduction rate of halophilic denitrifiers was much less than the freshwater counterpart. Halophilic activated sludge was characterized as good settling and flocculation prosperity with small floc size and net-like sludge structure. The abundance of ammonia-oxidizing bacteria outnumbered ammonia-oxidizing archaeas in both estuarine sediments and the activated sludge. Nitrifier population was dominated by the halophilic members of genus Nitrosomonas. This study demonstrated the application of mixed halophilic consortia for efficient nitrogen removal, overcoming the limits and difficulties of applying freshwater bacteria for saline wastewater treatment.

Background and purpose: Ammonia-Nitrogen is considered one of the environmental pollutants, these pollutants have high concentrations in petrochemical effluent specially, Ammonia and Urea plants. In this study, biological methods using native bacteria consertium isolated from petrochemical industry has been used for nitrate and ammonia removal.Methods: This study has been carreid out in batch mode and the effects of initial concentrations; pH and retention time has been investigated. The initial concentrations of 3×108 CFU/ml of nitrifier and denitrifier bacteria has been used. An initial ammonia and nitrate concentrations of 50-200 mg/l as well as the retention time 3-168 hours and also pH 5, 6, 7, 8 and 9 were studied.Finding: The results showed that the native bacteria isoated from petrochemical industry with a population of 3×108 CFU/ml in pH 8 were able to remove ammonia and nitrate with a initial concentrations of 200 mg/l with 99.5% efficiency in a retention time 4 days for nitrifier, and 6 days for denitrifier bacteria.Discussion and conclusion: The isolated native bacteria had a powerful effect in the nitrification and denitrification processes, so effluent ammonia can be removed with high efficiency by isolated native bacteria, and needs for environmental standards can be applied for effluent discharge.

In this study, the nitrification process using enriched ammonia oxidizing bacteria was used for ammonium removal from coke wastewater of Isfahan Steel Company (ISCO). Influent and effluent samples containing ~600 mg 1-1 ammonium and 2530-550 mg 1-1 phenol were collected. For comparative assessment, ammonia removal was performed on artificial media in which removal of ammonium took a shorter time (8 days) than in the real wastewater. Ammonium removal efficiency from the effluent was higher than that from the influent due to the reduced phenol content in the former. The best result occurred in the treatment composed of effluent, enriched nitrifies, and bicarbonate for which a record ammonium removal of 14 days was observed. MPN method was used to count and compare colonies of nitrifying bacteria in the samples. The enriched nitrifier sample containing 4.6x103 cell ml-1 was the best. The results show that phenol has inhibitory effects on nitrification. Carbonate ions and enriched nitrifying bacteria have positive effects on ammonium removal in all samples.

Aerobic biofilm systems are increasingly used for household wastewater treatment, but little is known about their potential to emit nitrous oxide in response to different loading conditions. We studied nitrification and nitrous oxide production in a biofilm reactor that was continuously fed with three different mixtures of household wastewater. Higher proportions of blackwater increased nitrification activity, which resulted in enhanced nitrite accumulation and nitrous oxide emissions. Applying a conceptual biofilm model together with the results of ancillary batch incubations suggested that this was caused by a higher proportion of slowly degradable compounds in blackwater. Increasing amounts of blackwater would result in less oxygen depletion by heterotrophic degradation in outer biofilm layers, leading to nitrite accumulation by enhanced ammonia oxidation as well as electron limitation of denitrification in anoxic biofilm layers. Under such conditions, nitrifier denitrification and incomplete heterotrophic denitrification would be the prevailing sources of nitrous oxide emission. These assumptions are supported by an exponential increase in the determined emission factor (nitrous oxide relative to oxidized ammonia), which accounted for 0.7 with 20 % blackwater, 1.1 with 50 % blackwater, and 8.5 with 100 % blackwater in the wastewater load.

Background and objective: Petrochemical industry as well as some other industries is one of the environmental pollution which polluttted wastewater with ammonia nitrogen. The objective of this study was two-step ammonia nitrogen removal from Kermanshah Petrochemical effluent using native bacteria immobilized on granular activated carbon. Method: This study conducted in continuous mode using two reactors with effective volume of 1. 7 l for each reactor. These reactors operated as up-flow and fixed film. Granular activated carbon immobilized with nitrifier and denitrifire bacteria has been used as media. Initial concentrations of ammonia and nitrate (50-200 mg/l) with retention time (1-3 h) at pH 8 and temperature of 28 ± 3 ° C were studied. Findings: Results showed that with increasing in retention time in both reactors nitrification and denitrification efficiency increased. The maximum nitrification and denitrification rates were 2. 69 Kg NH4+/m3. d and 2. 49 Kg NO3-/m3. d respectively. Maximum nitrification and denitrification rates occurred at 3h retention time and ammonia and nitrate removal efficiency were achieved 99. 5 percent. Discossion and Conclusion: This study has been showed that native bacteria immobilized on granular activated carbon and use of that in a continuous up-flow attached-growth reactor for the removal of ammonia has a high efficiency.

Background: The present study aimed to assess the acute impact of erythromycin (ERY) as an inhibitor on peptone mixture utilization of activated sludge (AS) consortium. Methods: For this purpose, the inhibition of oxygen consumption was used based on the ISO 8192: 2007 procedure. In this method, the AS consortium (10-day age) was extracted from labscale membrane bioreactor, then, percentage inhibition for total, heterotrophic, and nitrifying microorganisms, in separate batch respirometric tests were calculated in the absence and presence of N-allylthiourea (ATU) as a specific Nitrification inhibitor. Results: The obtained data showed that the height of oxygen uptake rate (OUR) profiles and amount of oxygen consumption reduced with increasing ERY dose. The half-maximal effective concentration (EC50 ) of ERY for heterotrophic and nitrifier microorganisms were 269. 4 and 1243. 1 mg/L, respectively. In Run 1, the kinetic coefficients bH, fA, H, YH, and µ H were calculated as 2. 61 d-1, 0. 44, 0. 4945 mg VSS/mg COD, and 0. 047 d-1, respectively. Also, for maximum ERY concentration (1000 mg/L), the kinetic coefficients bH., fA, H, YH, and µ H were calculated as 2. 27 d-1, 0. 3, 0. 4983 mg VSS/mg COD, and 0. 0049 d-1, respectively. Conclusion: The findings showed that the inhibitory impact of ERY was observed as a decrease in the amount of oxygen consumption by OUR profiles in rapid respirometric method (ISO 8192), which offered a novel insight for the acute inhibitory impact of this antibiotic. Also, chemical oxygen demand (COD) as an overall substrate parameter is most helpful in interpreting the behavior and the metabolic functions of AS systems.

This study was conducted on a Typic Haplocalcids, coarse-loamy over loamy skeletal carbonatic, (hyper) thermic soil (alluvium-derived) at the Gareh Bygone Plain Experiment Station, 200 km to the south-east of Shiraz, Iran. Four composite samples of surface soil (0-20 cm) were collected from: (1) a control site without floodwater spreading. (2) The first two sedimentation basins (SBs) of the Bisheh Zardl artificial recharge of groundwater (ARG) system, where Eucalyptus camaldulensis had been planted in Jan.-Feb. 1983(EUCA). (3) SB2 and SB3 of the Rahim Abad, which formed the third treatment and were under native pasture and irrigated with floodwater. (4) Farm fields located at south-west of Bisheh Zard formed the fourth treatment (AF AR). These samples were used for enumeration of total bacteria and nitrifying bacteria by the Most Probable Number (MPN) method. It was observed that, in comparison with the control, the total population of the soil bacteria increased by about 34 and 24 fold, respectively, at the sites with Eucalyptus camaldulensis and native pasture along with floodwater spreadingl. Two former sites had about 6 and 4 fold more microorganisms as compared with the farm fields. An increase in moisture and substrate supply for the biotic community at these sites, are the two major determinants. Amounts of organic matter in the site planted with E. camaldulensis, had increased by about 2-fold in comparison with control and farm fields (1.40% versus 0.63% and 0.73%, respectively). The number of ammonium oxidizers in EUCA and AFAR sites increased significantly.The number of both ammonium and nitrite oxidizers (nitrifiers) was more in the site with E. camaldulensis than the other sites. It may be concluded that cultivation of E. camaldulensis stimulates the growth and activity of nitrifier bacteria and subsequently, nitrification.

The treatment of wastewater generated from acrylonitrile butadiene styrene (ABS) resin manufacturing industry have a great importance due to its high chemical oxygen demand (COD) and some other toxic substances. Activated carbon adsorption, chemical oxidation and biodegradation are the most conventional methods to the treatment of ABS effluents. Among them, the biological treatment as an environmentally friendly technology is highly regarded in the bio treatment and biotransformation of the toxic compounds of ABS wastewater to the intermediate and final compounds such as CO2 and water. This study was conducted to evaluate the performance of an activated sludge system for pretreating ABS manufacturing effluents. The wastewater pretreatment plant is consisted of 3 fine screens, a grit chamber, an equalization basin, dissolved air floatation (DAF) system, an activated sludge reactor and a final clarifier. This system was operated to reduce the TSS and COD values in the effluent in order to obtain to interior discharge permits to the central wastewater treatment utility operated by Tabriz petrochemical complex. Four runs weighed average sampling was conducted during 6 months according to the standard methods of the examination of water and wastewater. The parameters including COD, BOD5, TSS, TDS, sulfate, total kjeldahl nitrogen (TKN), ammonia-N, nitrate-N, alkalinity, cyanide, phosphate and pH were measured in wastewater samples according to the standard methods. The concentrations of acrylonitrile, acrylamide and acrylic acid in wastewater samples were determined using gas chromatography (GC) equipped with flame ionization detector (FID) with capillary column. Microbial structure of activated sludge was also evaluated using R2A, PCA and Nutrient Agar culture media as well the biochemical standard tests. According to the results, at surface loading rate of 2.76 m3/m2.h applied to DAF, the COD and TSS removal efficiencies of 24 and 43% were obtained, respectively. The ratio of BOD5/COD in the influent was 0.57 indicated the moderate biodegradability of ABS wastewater. In addition, the COD and BOD5 removal efficiencies in biological reactor were 59 and 68% respectively, at the organic loading rates (OLR) of 0.79±0.06 kgCOD/m3.d. Totally, the COD, BOD5 and TSS removal efficiencies in the pretreatment system were 80, 90 and 88%, respectively. In addition, at the acrylonitrile loading rates of 0.067±0.008 kg ACN/ m3.d, the removal efficiency of acrylonitrile was 91% which 26% of that has occurred in the biological reactor. Also, the removal efficiency of cyanide was 97% which only 4% of that has occurred in the biological reactor. Twenty bacterial strains were isolated and identified from the activated sludge samples. Among the isolated bacterial strains, four strains include Alcaligenes sp. Pseudomonas sp. Bacillus sp. and Moraxella sp. were identified as heterotrophic nitrifiers. Based on the results, the nitrifier bacteria have played an important role in the degradation of acrylonitrile in the biological activated sludge system. The results of parameters analysis, performance evaluation and microbial assessment revealed the satisfactory performance of COD removal as well nitrification. However, it seems that a significant portion of the volatile organic compounds (VOCs) are removed from the influent wastewater by stripping.