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N2O emission was studied in a continuous process via nitrite for real urban wastewater treatment. The relationship between the gaseous forms and the liquid kinetic rates of nitritation and denitritation was investigated. N2O mass load and global nitrogen mass balance were quantified. The emission factor of the N2O (gN2Oemitted/kg mixed liquor volatile suspended solids [MLVSS]/d) was calculated. Incrementing the nitritation rate permits the reduction of N2O emission by 78%. Instead, an N2O decrease of 93% was observed by increasing the denitritation velocity. The determinant role of the anoxic phase in the production of dinitrogen oxide was identified. The contribution of N2OO emission from the anoxic phase (4.8 gN2O-N/kgMLVSS/d) was enhanced under limiting denitritation conditions (kd lower than 0.08 kgNOx-N/kgMLVSS/d). N2O production increased by five times with the accumulation of nitrites in the solution up to 200 mg/L. Strict correlation between free ammonia concentration and nitritation rate was found as a possible signal of further ammonia oxidizing bacteria selection. [ABSTRACT FROM AUTHOR]

Two advanced biological solutions for sludge minimization in wastewater treatment are tested. The first solution, particularly suitable for new installations, is based on the application of the sequential batch biofilter granular reactor (SBBGR). The second one, mostly appropriate for existing plants, is the alternate cycles process applied in the sludge line (ACSL) of conventional activated sludge systems. The results of treating raw municipal wastewater show that the SBBGR system is able to reduce the quantity of sludge up to 80%. Furthermore, the produced excess sludge requires no longer stabilization compared with the usual aerobic/anaerobic one. As regards the ACSL process, the results obtained in the full scale have shown an observed sludge yield reduction up to 54% with an increase in the specific oxygen uptake rate up to 20 mgO2/gVSS/h. Finally, applying the ACSL process low specific consumption of energy is required. [ABSTRACT FROM AUTHOR]

The study involved the optimization of the flow scheme of a full-scale platform for industrial liquid wastes. Non-hazardous liquid wastes from natural gas extraction (spent brine) represent 26% of the total influent wastes. For elevated salinity this waste is strongly inhibitory for traditional biological processes. The implementation of the treatment solution is represented by advanced oxidation with ozone in a separate line to remove the ammonia nitrogen with the direct transformation in nitrogen gas. The ratio of bromides/nitrogen greater than 0.4 was evaluated as being the determining factor to activate the process. Ammonia, without the formation of secondary nitrogen compounds, decreases up to 21 mgL−1dosing 300 mgO3 L−1and equal to 0 mgL−1at maximum ozone. In addition, the catalytic effect of bromides determines a reduction of nitrate to final concentrations of 5 mgL−1. Any carcinogenic compounds, such as bromates, or residual stripped ammonia were not noted. The economical evaluation was reported. [ABSTRACT FROM AUTHOR]

The produced nitrogen oxides from the biological treatment of swine and dairy anaerobic supernatant are evaluated. The quantification of the emissions has been conducted in a continuous way and coupled with batch tests to determine the mechanisms of formation. Using a continuous monitoring system, N2O and NO forms are present in higher quantities than NO2. The elevated emissions are linked with the increment of the influent nitrogen load both in the daily variations and in the long period. The NH4–N and NO2–N accumulations are recognized as the main parameters which determine the great nitrogen oxide emissions even at dissolved oxygen concentration of around 2 mgL−1. The nitrogen oxides’ impacts are between 0.0034 and 0.0044N% for the N2O and between 0.0020 and 0.0026N% for NO. A strict dependence between the N2O and the oxidation reduction potential is found. [ABSTRACT FROM AUTHOR]

The biological solution proposed to reduce the wasted sludge production is based on a process of alternating phases realized in a specific reactor (alternate cycles in sludge line (ACSL)) where a quote of the recycle sludge is treated and sent back to the main activated sludge process. The ACSL process was applied in two urban wastewater treatment plants (WWTPs). The reduction was tested by changing the hydraulic retention time and the conditions of oxidation reduction potential. The main mechanism of the process is recognized in the metabolic uncoupling. In fact, an increase in the specific oxygen uptake rate in the biological reactors was recorded (up to 20 mg/g VSS/h), which was stimulated by the fasting condition in the ACSL. The process is able to reduce the observed sludge yield on average of 25–30% with final average values reaching 0.179 kg VSS/kg chemical oxygen demand (COD) for WWTP1 and 0.117 kg VSS/kg COD for WWTP2. [ABSTRACT FROM PUBLISHER]

The treatment of industrial liquid wastes is placed in a wide context of technologies and is related to the high variability of the influent physical-chemical characteristics. In this condition, the achievement of satisfactory biological unit efficiency could be complicated. An alternate process (AC) with aerobic and anoxic phases fed in a continuous way was evaluated as an operative solution to optimize the performance of the biological reactor in a platform for the treatment of industrial liquid wastes. The process application has determined a stable quality effluent with an average concentration of 25 mg TN L-1, according to the law limits. The use of discharged wastewaters as rapid carbon sources to support the anoxic phase of the alternate cycle, realizes a reduction of TN of 95% without impact on the total operative costs. The evaluation of the micro-pollutants behaviour has highlighted a bio-adsorption phenomenon in the first reactor. The implementation of the process defined 31% of energy saving during period it and 19% for the periods 2, 3 and 4. [ABSTRACT FROM AUTHOR]