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Development of digesters with an external zeolite column facilitates the convenient removal of the zeolite with TAN, without disturbing the continuous anaerobic digestion process. A digester with an inside zeolite bed (In-Zeo) and digester without adding zeolite (No-Zeo) were employed to compare the process performance with digester with external zeolite column (EX-Zeo). The cumulative, CH4 yields were 5% and 15% greater in the EX-Zeo, and the In-Zeo digesters respectively compared to the No-Zeo digesters. Also, the % VS reduction was 49%, 55% and 41%, respectively in the Ex-Zeo, In-Zeo and No-Zeo digesters. The results indicated that treatment with 7% zeolite during anaerobic digestion has the potential to improve biodegradation of swine manure. The addition of zeolite appeared to reduce TAN from the digestate, thereby enhancing the CH4 yield. Zeolite could be used either internally or externally to enhance CH4 production through anaerobic digestion of swine manure. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the feasibility of using natural and NaCl-treated Australian zeolites to simultaneously remove excess nutrients from anaerobically digested swine manure. Ion adsorption and desorption properties of Australian zeolite during the anaerobic digestion of swine manure were investigated. Two experiments were conducted: the first was an adsorption experiment with multi-component solutions that corresponded with the ionic composition of swine manure digestates. The second experiment determined the effects of zeolite dose rates during anaerobic digestion of swine manure on the removal of N, P and K from solution. Adsorption isotherms confirmed selectivity for K+over NH4+by Australian natural and sodium zeolites. Therefore, NH4+removal was considerably reduced when there was simultaneous K+uptake. Natural zeolite desorbed more Ca2+during K+and NH4+adsorption than sodium zeolite. The ion exchange reaction was independent of the presence of P. P removal was very dependent on the pH of the medium. Natural Australian zeolite was shown to be a potential sorbent for the removal of NH4+, K+and P during the anaerobic digestion of swine manure. However, the application of high concentrations of zeolite at higher pH values (> 7.5) might not be appropriate for anaerobic digestion, because zeolite desorbed more Ca2+ions into the solution at the higher doses of zeolite and then availability of P for microbial growth might be reduced as a result of PO43−precipitation with Ca2+at the higher pH. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is one of the most effective methods for treating swine manure by converting it into green energy, and efficiently reducing methane (CH 4 ) emission to the atmosphere. Low C/N ratio of swine manure and the production of high levels of total ammoniacal nitrogen (TAN) during acidogenesis due to the high N contents of swine manure considerably reduce CH 4 yield. The reduction of N during anaerobic digestion by the addition of zeolite improves CH 4 production and reduces potential environmental threats associated with ammonia (NH 3 ) emissions from anaerobic digestion of swine manure. The main objective of this study was to determine the optimum Australian zeolite dose that produces maximum NH 4 + recovery at optimum CH 4 production. In laboratory experiments, swine manure was treated with natural and sodium zeolites at 0, 10, 40, 70, 100 mg/L and digested anaerobically for 60 days. Natural zeolite at a dose of 40 g/L resulted in the largest increase (29%) in total CH 4 yield from swine manure compared to the nil zeolite treatments. The lag phase of digestion was decreased with increasing zeolite doses up to 100 g/L. Natural and sodium zeolites at a dose of 100 g/L reduced NH 4 + by 50% and 52% in the media, respectively, compared to the nil zeolite treatments. However, the increases in CH 4 yield of natural and sodium zeolites at a dose of 100 g/L were only 10% and 12%, respectively. Variations of cation concentrations in the digesters caused by adding zeolite at different rates might be a reason for variation of biogas and CH 4 productions from various rates of zeolites digesters. [ABSTRACT FROM AUTHOR]

Removal of ammonium nitrogen (NH4+-N) particularly from sources which are highly rich in nitrogen is important for addressing environmental pollution. Zeolites, aluminosilicate minerals, are commonly used as commercial adsorbents and ion-exchange medium in number of commercial applications due to its high adsorption capacity of ammonium (NH4+). However, detailed investigations on NH4+ adsorption and ion exchange capacities of Australian natural zeolites are rare, particularly under higher NH4+ concentrations in the medium. Therefore, this study was conducted to determine NH4+ adsorption characteristics of Australian natural zeolites at high NH4+ concentrations with and without other chemical compounds in an aqueous solution. Results showed that initial NH4+ concentration, temperature, reaction time, and pH of the solution had significant effects on NH4+ adsorption capacity of zeolite. Increased retention time and temperature generally had a positive impact on adsorption. Freundlich model fitted well with adsorption process of Australian natural zeolites; however, Langmuir model had best fitted for the adsorption process of sodium (Na+) treated zeolites. NaCl treatment increased the NH4+ adsorption capacity of Australian zeolites by 25% at 1000 mg-N, NH4+ solution. The maximum adsorption capacity of both natural Australian zeolites and Na+ treated zeolites were estimated as 9.48 and 11.83 mg-N/g, respectively, which is lower than many zeolites from other sources. Compared to the NH4+ only medium, presence of other competitive ions and acetic acid in the medium (resembling composition in digested swine manure slurries) reduced NH4+ removal of natural and Na+ treated zeolites by 44% and 57%, respectively. This suggests detailed investigations are required to determine practically achievable NH4+ -N removal potential of zeolites for applications in complex mediums such as animal manure slurries. [ABSTRACT FROM AUTHOR]