Ammonia removal from anaerobically digested dairy manure by struvite precipitation

Ammonia is one of the most important contaminants impairing the quality of water resources. When this is considered along with the fact that the global demand for nitrogenous fertilizers is in constant rise, the need for recovery as well as removal of nitrogen is well justified. Crystallization of N and P in the form of struvite (MgNH4PO4 center dot 6H(2)O), which is a slow releasing and valuable fertilizer, is one possible technique for this purpose. This study investigated the removal of NR4+ through struvite precipitation from the effluents of one- (R1) and two-phase (R2) anaerobic reactors digesting dairy manure. To force the formation of struvite in the anaerobic reactor effluents, Ma(2+) ion was added by using both Mg(OH)(2) and MgCl2 center dot 6H(2)O. To prevent the effect of different total phosphorus (TP) concentration in the effluents of RI and R2, as well as to not limit the formation of struvite, an excess amount Of PO43- (0.14 M) was added in the form of NaHPO4. Different stoichiometric Mg2+:NH4+:PO43- ratios were tested to determine the required Mg2+ concentrations for maximum NH4+ removal by keeping NH4+:PO43- ratio constant for the effluents of reactors RI and R2. The results revealed that very high NH4+ removal efficiencies (above 95%) were possible by adding Mg 21 ions higher than 0.06 M concentration in the effluents from reactors RI and R2. It was also observed that the initial pH adjustment to 8.50 using NaOH did not result in any significant increase in the removal of NH4+ and the removal of NH4+ in the reactors treated with MgCl2 center dot 6H(2)O was higher than those treated with Mg(OH)(2) for the same Mg2+ concentration. (c) 2005 Published by Elsevier Ltd

Comparison of methods for estimating carbonaceous BOD parameters

The performance of seven different methods (Differential, Fujimoto, Thomas, Graphical, Integral, Log-Difference, and Nonlinear Regression) for estimating first-stage, carbonaceous biochemical oxygen demand (CBOD), curve parameters, namely k and L-0 were compared using synthetic data generated by Monte Carlo simulation technique. The comparison of the methods was made based on their efficiency in retrieving the original values of k and L-0 which were selected to generate the synthetic data. In the first part of the study, five sets of "true" data (without error substitution) with different k and L-0 value pairs, (k (d(-1))-L-0 (mg l(-1)): 0.23-10,000; 0.23-250; 0.23-50; 0.10-250; and 0.50-250) were used to obtain information about the effect of different k-L-0 combinations and of using 5-day and 20-day CBOD data on the performance of the methods. In the second part, the same methods were used to calculate k and L-0 for ten sets of synthetic data with log-normally distributed random errors at the coefficient of variation (COV) levels of 0.1, 0.2, and 0.3 for a single k-L-0 value pair, (0.23 d(-1); 250 mg l(-1)). The results indicated that: (1) different combinations of k-L-0 values had no significant effect on the performance of CBOD curve parameter estimation methods with the "true" data; (2) use of CBOD20, data, i.e., CBOD data collected for 20 days, provided better estimates fork and L-0; (3) the Integral and Nonlinear Regression techniques were found to be the most reliable methods for the estimation of CBOD curve parameters among the other methods considered in this study

Control of trichloroethylene emissions from sparging systems by horizontal bio- and chemo-barriers

The scope of this study was to develop a continuous system to clean-up a trichloroethylene (TCE) contaminated gas stream, where biotic and abiotic removal mechanisms are undertaken sequentially simulating the horizontal bio- and chemo-barriers proposed for the in-situ remediation of the contaminated sites. The bio- and chemo-barriers were simulated by using glass columns packed with granular anaerobic mixed culture and Fe(0) filings, respectively. The effect of gas residence time, which is adjusted by the gas flowrate, on the TCE removal efficiency of the reactor system was investigated. TCE removal efficiency of over 90% was achieved at gas residence times above 1hr. Furthermore, the effluent of reactor system contained only ethane and ethylene, which are non-toxic by-products of TCE reduction reactions, along with trace amounts of TCE

Wzbogacanie pożywki anaerobowych osadów ściekowych przez współstrącanie N i P w mezofilowym fermentatorze anaerobowym

Copper One of the techniques used for the stabilization of sewage sludge is anaerobic digestion. The effluent from anaerobic digesters usually requires further treatment since they contain high concentrations of N and P as a result of volatile solids destruction. In this study, a control was developed over the nutrient ions within the anaerobic digester by using substrate with high concentration of Mg2+ ion. The amount of Mg2+ ion added was determined based on the release rate of N and composition of magnesium ammonium phosphate. The results showed 50% removal of NH4+ and PO43- can be achieved without compromising the performance of the reactor in COD and VSS removal and biogas formation.Jedną z technik użytych do stabilizacji osadów ściekowych jest fermentacja beztlenowa. Ścieki z komór fermentacyjnych zwykle wymagają dalszej obróbki ze względu na fakt, że zawierają wysokie stężenia N i P jako rezultat rozkładu substancji stałych. W referacie zamieszczono wyniki kontroli nad jonami substancji odżywczych w obrębie komory fermentacyjnej przez użycie substratu o wysokim stężenie jonów Mg2+. Ilość dodanych jonów Mg2+ określono na podstawie stopnia uwolnienia N i składu fosforanu amonu magnezu. Wyniki pokazują 50% usuwalność NH4+ i PO43- co może być osiągnięte bez kompromisu pomiędzy wydajnością reaktora COD a usuwalnością VSS i tworzeniem biogazu

Removal of ammonium and phosphate from the supernatant of anaerobically digested waste activated sludge by chemical precipitation

The removal of ammonium (NH4+) and phosphate (PO43 -) from supernatant of anaerobic digestion by magnesium ammonium phosphate (MAP) formation was studied. To be able to find out the loss of NH4+ by its transformation to NH3, rates of NH4+ removal by aeration and by MAP formation combined with aeration were compared. NH4+ removal by aeration was found to be insignificant. The kinetics of MAP formation was fast. The removal rate of NH4+ and Mg2+ was the smallest and the largest, respectively based on rate constants calculated. The removal of NH4+ showed sensitivity to Mg2+ and PO43 - concentrations and controlled the purity of MAP precipitate. The removal of PO43 - was found to be sensitive to mainly Mg2+ ion. These results also indicated that as the supernatant solution became more saturated in terms of MAP forming ions, the effect of pH increase became insignificant in the removal of ions from the solution

Anaerobic digestion of dairy manure with enhanced ammonia removal

Poor ammonia-nitrogen removal in methanogenic anaerobic reactors digesting animal manure has been reported as an important disadvantage of anaerobic digestion (AD) in several studies. Development of anaerobic processes that are capable of producing reduced ammonia-nitrogen levels in their effluent is one of the areas where further research must be pursued if AD technology is to be made more effective and economically advantageous. One approach to removing ammonia from anaerobically digested effluents is the forced precipitation of magnesium ammonium phosphate hexahydrate (MgNH4PO4-6H(2)O), commonly called struvite. Struvite is a valuable plant nutrient source for nitrogen and phosphorus since it releases them slowly and has non-burning features because of its low solubility in water. This study investigated coupling AD and controlled struvite precipitation in the same reactor to minimize the nitrogen removal costs and possibly increase the performance of the AD by reducing the ammonia concentration which has an adverse effect oil anaerobic bacteria. The results indicated that Lip to 19% extra COD and almost 11% extra NH3 removals were achieved relative to a control by adding 1750 mg/L of MgCl2-6H(2)O to the anaerobic reactor