Total Ammoniacal Nitrogen Concentrations Research Articles

Influence of key factors on ammonia and nitrous oxide emission factors for excreta deposited by livestock and land-applied manure

Ammonia (NH3) and nitrous oxide (N2O) emissions from livestock manure management have a significant impact on air quality and climate change. There is an increasing urgency to improve our understanding of drivers influencing these emissions. We analysed the DATAMAN (“DATAbase for MANaging greenhouse gas and ammonia emissions factors”) database to identify key factors influencing (i) NH3 emission factors (EFs) for cattle and swine manure applied to land and (ii) N2O EFs for cattle and swine manure applied to land, and (iii) cattle urine, dung and sheep urine deposited during grazing. Slurry dry matter (DM) content, total ammoniacal nitrogen (TAN) concentration and method of application were significant drivers of NH3 EFs from cattle and swine slurry. Mixed effect models explained 14–59 % of the variance in NH3 EFs. Apart from the method of application, the significant influence of manure DM, manure TAN concentration or pH on NH3 EFs suggests mitigation strategies should focus on these. Identifying key factors influencing N2O EFs from manures and livestock grazing was more challenging, likely because of the complexities associated with microbial processes and soil physical properties impacting N2O production and emissions. Generally, significant factors were soil-related e.g. soil water content, pH, clay content, suggesting mitigations may need to consider the conditions of the receiving environment for manure spreading and grazing deposition. Total variability explained by terms in mixed effect model was on average 66 %, with the random effect ‘experiment identification number’ explaining, on average, 41 % of the total variability in the models. We suspect this term captured the effect of non-measured manure, soil and climate factors and any biases in application and measurement technique effects associated with individual experiments. This analysis has helped to improve our understanding of key factors of NH3 and N2O EFs for inclusion within models. With more studies over time, insights into the underlying processes influencing emissions will be further improved.

Model for calculating ammonia emission from stored animal liquid manure

Ammonia (NH3) emissions from agriculture have increased by 90% from 1970 to 2005, and agriculture is now the largest source of NH3 to the atmosphere. Calculated national NH3 emissions from agriculture using static emission factors do not reflect regional conditions. We propose, parameterize and test a simple model to calculate emission rates which incorporates effects of temperature, pH, total ammoniacal nitrogen (TAN) concentration, exposed storage area, and storage cover. This is the first time that several known algorithms were combined in this semi-dynamic user-friendly model concept and that model parameters (uploaded on the internet) were estimated from a unique database comprising 44 studies. The calculator is designed to be used correctly even if there exists only little knowledge about manure chemistry or micrometeorology, and can calculate emissions with a low demand for input data Calculations using the new model are as accurate as the standard method. The proposed approach has two advantages compared to the standard alternative: it does not require an estimate of TAN flow through the store, and calculated values reflect management (e.g., storage area or covers), TAN concentration, pH and temperature based on well-established principles. The simple and process-related approach has the potential to deliver more accurate estimates after a more precise parameterization from dedicated studies where the focus is on emission measurements, slurry composition characterization, air and slurry temperature and turbulence. To facilitate this approach, data need to be collected over relatively short time intervals (less than twice per day) to ensure that they cover cardinal diurnal conditions at the same time and right place. A spreadsheet implementation of the model is publicly available from https://github.com/sashahafner/AMOSTO.

Does feeding more phases reduce ammonia concentrations from broiler litter?

We compared a 3- and 5-phase feeding program in terms of ammonia concentrations measured at litter level, litter composition and quality, nitrogen (N) utilization, performance, welfare, and meat deposition in broilers. A total of 744 Ross 308 male broilers was divided into 2 treatments, each with 6 replicates. The 3-phase diets were formulated to CP and digestible lysine contents of 205 and 11.5 g/kg (0 to 9 d), 195 and 10.8 g/kg (9 to 24 d), and 183.3 and 10.15 g/kg (24 to 39 d), respectively. The 5-phase diets had additional phases from 17 to 24 d and 32 to 39 d with CP and digestible lysine contents of 188 and 10.4 g/kg and 177 and 9.8 g/kg, respectively. Feeding 5 phases reduced the NH3 concentrations at litter level by 37.95% and 20.81% at 23 (P < 0.05) and 37 d of age (P < 0.05), respectively. There was a tendency for a lower litter total ammoniacal nitrogen concentration for the 5-phase treatment than the 3-phase treatment at 24 and 39 d of age (P < 0.1 for both). Total N concentration of the litter also tended to be lower for the 5-phase treatment at 39 d of age (P < 0.1). The lower NH3 coincided with a lower average litter pH at 24 and 32 d of age (P < 0.05 for both). Birds fed the 5-phase treatments had a lower incidence of foot lesions at 24 d of age (P < 0.001). Performance as well as carcass yield could be maintained, except for FCR, which was higher for the 5-phase treatment between 17 and 24 d of age and the overall period (P < 0.05 and < 0.001, respectively). The impact of the 5-phase treatment regarding the utilization of N (digestibility, excretion, and retention) was less clear, however the NH3 volatilized from the litter was significantly reduced. Feeding 5 phases may therefore potentially reduce the NH3 emitted from broiler houses which has several environmental and health benefits. Although the 5-phase treatment resulted in a significant decrease in feed efficiency, growth performance and meat deposition were maintained.

Treatment of a slaughterhouse wastewater by anoxic-aerobic biological reactors followed by UV-C disinfection and microalgae bioremediation.

In this study, removal of organic matter and nitrogen from a cattle slaughterhouse wastewater was investigated in a two-stage anoxic-aerobic biological system, followed by UV-C disinfection. Ecotoxicity of the raw, biotreated, and disinfected wastewater against the microalgae Scenedesmus sp. was evaluated in short-term tests, while the potential of the microalgae as a nutrient removal step was addressed in long-term experiments. Throughout 5 operational phases, the biological system was subjected to gradual reduction of the hydraulic retention time (8-1.5day), increasing the organic (0.21-1.11kgCOD·m-3 ·day-1 ) and nitrogen (0.05-0.28kgN·m-3 ·day-1 ) loading rates. COD and total ammoniacal nitrogen (TAN) removal ranged within 83%-97% and 83%-99%, respectively. While providing alkalinity source, effluent TAN concentrations were below 5mg·L-1 . Nitrate was the main nitrification product, while nitrite levels remained low (<1mgN·L-1 ). Upon supplementation of external COD as ethanol, total nitrogen removal reached up to 90% at the highest load (0.28kgN·m-3 ·day-1 ). After UV-C treatment, 3-log reduction of total coliforms was attained. The 96-hr ecotoxicity tests showed that all non-diluted samples tested (raw, biologically treated and UV-C irradiated wastewater) were toxic to microalgae. Nevertheless, these organisms were able to acclimate and grow under the imposed conditions, allowing to achieve nitrogen and phosphorous removal up to 99.1% and 43.0%, respectively. PRACTITIONER POINTS: The treatment of a slaughterhouse wastewater in an anoxic-aerobic biological system followed by a UV-C disinfection step was assessed. The pre-denitrification system showed efficient simultaneous removal of organic matter and nitrogen from the wastewater under increasing applied loads. UV-C disinfection worked effectively in reducing coliforms from the biotreated effluent, boosting the performance of microalgae on nutrients removal. Despite the toxicity to microalgae, they were capable to acclimate to the aqueous matrices tested, reducing efficiently the nutrients content. The combined stages of treatment presented great capacity for depleting up to 97% COD, 99% nitrogen, and 43% phosphorous.

Compartmental process-based model for estimating ammonia emissions from stored liquid dairy manure

This study developed a compartmental process-based model (PBM) as an alternative approach to estimate ammonia emission from liquid dairy manure during storage to improve the accuracy of quantification tools for nitrogen cycling at the farm level compared to the currently used non-compartmental PBM. The compartmental PBM developed partitions stored manure into several layers in the vertical domain to facilitate the spatial temperature and substrate concentration calculations. In contrast, the non-compartmental PBMs currently used consider the bulk stored manure as a material with homogenous properties. The models used similar equations and processes from the well-established principles of heat and mass transfer and pertinent known biogeochemical processes for the production and emission of ammonia. The models were calibrated, and their performance assessed using literature-based experimentally derived ammonia emission rates. Additionally, a scenario analysis was conducted to compare ammonia emission rate estimates by the models from stored liquid manure at a dairy farm during two (cold and warm) storage periods. Model outputs were sensitive to ambient air temperature, manure pH, wind speed, manure total ammoniacal nitrogen concentration, and the two-way interactions of ambient air temperature, pH, and wind speed. Ammonia emission rates by the models and literature-based experimentally derived ammonia emission rates were similar (p > 0.05). In general, the compartmental PBM predicted lower ammonia emission rates compared to the non-compartmental PBM. Also, the compartmental PBM had a relatively better performance compared to the non-compartmental PBM. Compared to the non-compartmental PBM, the compartmental model estimated lower ammonia emission rates, i.e., 28% and 34%, for the cold and warm periods, respectively.

Ammonia Volatilization Losses during Irrigation of Liquid Animal Manure

Ammonia loss resulting from land application of liquid animal manure varies depending on the composition of the manure and the method used to apply manure to cropland. High levels of ammonia volatilization result in an economic loss to the farmer based on the value of the nitrogen and have also been shown to be a source of air pollution. Using irrigation as a method of applying liquid manure to cropland has generally been accepted as a method that increases the volatilization of ammonia. However, only three studies available in the literature measured the amount of ammonia lost during the irrigation process. Only one of the three studies concluded that ammonia loss during irrigation was significant. A pooled statistical and uncertainty analysis of the 55 available observations was performed to determine if ammonia loss occurred during irrigation of animal manure. Data on the total solids content of the manure were also included as an indicator of evaporation losses. Volatilization losses during irrigation were not found to be statistically significant, and evaporation losses were small, 2.4%, and agreed with previous studies on irrigation performance. Furthermore, the range of ammonia loss reported in previous studies was determined to be within the errors associated with the measurement of total ammoniacal nitrogen concentrations and the calculation of per cent differences.

Insights from using in-situ ultraviolet–visible spectroscopy to assess nitrogen treatment and subsurface dynamics in a regenerative stormwater conveyance (RSC) system

Regenerative stormwater conveyance (RSC) is a recently developed stormwater control measure that marries the concepts of bioretention and stream restoration. RSC mitigates stormwater runoff by converting surface flow to subsurface seepage using a series of pools and riffles built over a sand media bed. Subsurface seepage flows through media and exits the RSC beneath the outlet weir. Previous studies on RSC pollutant mitigation have focused on surface flow discharges from the RSC. To date, no known research has been conducted on the potential pollutant contributions of RSC seepage, despite the fact that this water also enters receiving waters. This research used Multi-Point Sampling coupled with in-situ ultraviolet–visual spectroscopy to measure nitrogen in seepage during simulated storm events (n = 9) at a field-scale RSC in Raleigh, North Carolina. Calibrations between light absorbance and concentrations were acceptable (Nash-Sutcliffe coefficient > 0.65) for nitrate and total ammoniacal nitrogen (TAN) and very good (Nash-Sutcliffe coefficient > 0.90) for total Kjehdahl nitrogen (TKN). Early storm simulations revealed some initial nutrient flushing from the substrate, which subsided by the third simulation. Overall, subsurface seepage nitrate, TAN, and TKN concentrations were lower by 29%, 57%, and 4% relative to storm inflow concentrations, respectively. Computed subsurface nitrogen concentrations demonstrated temporal variability, highlighting dynamic transport and biogeochemical transformations in saturated and unsaturated conditions. Nitrogen concentrations were lower in seepage than in surface flow; however, due to the high volume of runoff converted to seepage, nitrogen loads discharged in seepage can be larger than those of surface flow. Further research is needed to examine subsurface pollutant reductions under varying hydrologic and seasonal conditions.

Ammonia stress on a resilient mesophilic anaerobic inoculum: Methane production, microbial community, and putative metabolic pathways

Short term inhibition tests, 16S rRNA tag sequencing and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt), were employed to visualise the effects of increasing total ammoniacal nitrogen (TAN) concentration (3400–10166 ppm TAN) on microbial community structure and metabolic pathways for acetate degradation. The rate of methane production on acetate was significantly reduced by TAN concentrations above 6133 ppm; however, methane continued to be produced, even at 10166 ppm TAN (0.026 ± 0.0003 gCOD.gVS−1inoculum.day−1). Hydrogenotrophic methanogenesis with syntrophic acetate oxidation (SAO) was identified as the dominant pathway for methane production. A shift towards SAO pathways at higher TAN concentrations and a decrease in the number of ‘gene hits’ for key genes in specific methanogenesis pathways was observed. Overall, the results highlighted potential for inhibition activity testing to be used together with PICRUSt, to estimate changes in microbial metabolism and to better understand microbial resilience in industrial AD facilities.

Characterising and modelling free ammonia and ammonium inhibition in anaerobic systems

Inhibition by ammoniacal nitrogen, consisting of free ammonia (NH3) and ammonium ion (NH4+), has been widely investigated for anaerobic digestion. However, despite the large amount of research on the subject, ammoniacal nitrogen inhibition still threatens many anaerobic digesters. This paper presents (i) a method to reliably characterise ammoniacal nitrogen inhibition and (ii) a robust inhibition modelling approach. Results showed that NH3 and NH4+ inhibition need to be jointly determined, which can only be done by performing inhibition tests at various total ammoniacal nitrogen (TAN) concentrations and pH values. These test conditions were reliably achieved using the salts NH4HCO3 and NH4Cl without pH adjustment, rather than by using NH4Cl with pH adjustment. The use of only salts showed a lower pH change during the inhibition test (∼1.5 days), thereby decreasing the uncertainty in TAN speciation and strengthening the test and model outputs. A threshold inhibition function satisfactorily described (R2 > 0.99) the joint inhibition of NH3 and NH4+ on three distinct inocula, and provided a better description of the inhibition testing results than a non-competitive inhibition function (R2 ∼0.70). The key advantage of the proposed threshold inhibition function is its capacity to identify the inhibition lower limit (concentration where inhibition starts; KImin) and upper limit (concentration where inhibition is complete; KImax). The threshold inhibition function also identifies the 50% inhibition concentration (KI50) at the midpoint of KImin and KImax. Finally, experimental and model results show that at pH 7.3–7.7 and TAN concentrations above 2000 mgN·L−1, both NH3 and NH4+ contribute significantly to overall inhibition.

Ammonia emissions from the field application of liquid dairy manure after anaerobic digestion or mechanical separation in Ontario, Canada

Anaerobic digestion (AD) and solid-liquid separation (SLS) are manure treatment strategies used on dairy farms. These treatments change manure characteristics, such as pH, dry matter, and total ammoniacal nitrogen (TAN) which affect ammonia (NH3) emissions after field application. This study used eight wind tunnels (1 m2 each) to compare the effects of application season and dairy manure treatment (AD vs SLS) on NH3 emissions. The highest cumulative NH3 emissions were seen in the spring from the AD manure treatment, which had higher TAN and pH compared to SLS. On the other hand, when normalized by TAN application rate there was no significant difference between AD and SLS manure in either spring (52 and 54% of TAN after 22 d, respectively) or fall (26% and 27% of TAN after 15 d, respectively). This suggests that if farmers adjusted application rates based on TAN content, NH3 emissions from applied AD manure could be minimized. Results were compared to the Ammonia Loss from Field Applied Manure (ALFAM) model. The model characterized the temporal pattern of emissions reasonably well in spring, but not fall. The model generally overestimated NH3 emissions during the first 24 h after application, and underestimated emissions after incorporation from day 2 to 22.

Evaluating the potential of dietary crude protein manipulation in reducing ammonia emissions from cattle and pig manure: A meta-analysis

Dietary manipulation of animal diets by reducing crude protein (CP) intake is a strategic NH3 abatement option as it reduces the overall nitrogen input at the very beginning of the manure management chain. This study presents a comprehensive meta-analysis of scientific literature on NH3 reductions following a reduction of CP in cattle and pig diets. Results indicate higher mean NH3 reductions of 17 ± 6% per %-point CP reduction for cattle as compared to 11 ± 6% for pigs. Variability in NH3 emission reduction estimates reported for different manure management stages and pig categories did not indicate a significant influence. Statistically significant relationships exist between CP reduction, NH3 emissions and total ammoniacal nitrogen content in manure for both pigs and cattle, with cattle revealing higher NH3 reductions and a clearer trend in relationships. This is attributed to the greater attention given to feed optimization in pigs relative to cattle and also due to the specific physiology of ruminants to efficiently recycle nitrogen in situations of low protein intake. The higher NH3 reductions in cattle highlights the opportunity to extend concepts of feed optimization from pigs and poultry to cattle production systems to further reduce NH3 emissions from livestock manure. The results presented help to accurately quantify the effects of NH3 abatement following reduced CP levels in animal diets distinguishing between animal types and other physiological factors. This is useful in the development of emission factors associated with reduced CP as an NH3 abatement option.

Transformation of Organic Matter and the Emissions of Methane and Ammonia during Storage of Liquid Manure as Affected by Acidification.

Acidification of livestock manure can reduce emission of the greenhouse gases methane (CH) and nitrous oxide (NO), as well as ammonia (NH). We examined the relation between emission of these gases and transformation of organic matter as affected by acidification. Liquid cattle manure was acidified with sulfuric acid to pH 5.5 at a pilot scale (100 L), and we measured effects on CH, NO, CO and NH emissions and on transformation of pH buffer components and organic matter. Acidification reduced NH emissions by 62% (47 d) and emission of CH by 68% (57 d). Emissions of NO were negligible, probably due to the absence of a surface crust. Reductions in NH and CH emission were highest at the start but declined over time concomitantly with a gradual increase in the stored liquid manure pH. Acidification did not significantly affect CO emissions. Emission of CO was high, five- to ten-fold of CH emissions, until Day 16 of storage, after which the CO emission rate declined to around twice the CH emission rate; consequently, the majority of C loss during the early stages of storage was CO. Cumulative emission of C in CO and CH closely matched depletion of dissolved organic carbon (DOC), suggesting that DOC may be a predictor for CH emission from dilute slurries. volatile fatty acid and total ammoniacal nitrogen concentrations in surface layers were substantially higher than at the center of stored liquid manure, perhaps resulting from microbial activity at the surface. This pattern deserves attention when predicting NH emission from stored slurry.

Dewatering of source-separated human urine for nitrogen recovery by membrane distillation

The nitrogen content of a synthetic ammonia wastewater was concentrated using direct contact membrane distillation (DCMD). The ratio of transferred ammonia to water (i.e., specific ammonia transfer: SAT) was controlled by operational conditions. With 20°C on the permeate side, and a high temperature of 70°C on the feed side, the process exhibited low SAT values for PTFE/PP (PTF045LD0A), PTFE/PP (TF-450), and PVDF (HVHP-14250) membranes. This was because the increase in water flux (>24L/m2h) was greater than that of ammonia transfer. A positive relationship between SAT and free ammonia concentration was identified under different total ammoniacal nitrogen concentration and pH. The acidification pretreatment to pH 5 led to further reduction in the SAT value (as low as 6.91×10−5g-N/g-H2O). As a practical application, the dewatering process of source-separated human urine by DCMD required an additional filtration step to prevent fouling, but the filtration had an insignificant effect on the SAT. For the acidified and filtered source-separated human urine, total ammoniacal nitrogen was successfully concentrated with a low SAT value (<2.06×10−3g-N/g-H2O).

Influence of Temperature and Ammonia on the High Solids Co-Digestion of Poultry Manure

Abstract. Solid-state anaerobic digestion (SSAD) of poultry manure was assessed to determine optimal operating ranges for temperature, moisture content and total ammoniacal nitrogen (TAN). SSAD was evidenced to be most efficient in mesophilic temperature ranges with influent total solids (TS) between 15% and 25%. Digestion at psychrophilic temperatures was infeasible and evidenced a steep decline in biogas yield in comparison to digestion at mesophilic temperatures. Digestion at thermophilic temperatures was inferior to mesophilic digestion, particularly at TAN concentrations above 3.5 g/L. Increases in TAN at 35°C resulted in slight process inhibition within the range investigated (2.5-4.5 g/L). At higher temperatures, TAN had a larger inhibitory effect on biogas yield. Co-digestion of poultry manure with grease and corn silage evidenced increased biogas yields of 22% and 44%, respectively, in comparison to digestion of poultry manure alone.

Effect of pH level and acid type on total ammoniacal nitrogen (TAN) retention and fouling of reverse osmosis membranes processing swine wastewater

Wastewaters fed to reverse osmosis (RO) membranes sometimes need to be acidified to prevent inorganic fouling and increase total ammoniacal nitrogen (TAN) retention. In this project, the effect of pH level (6.5–7.1) and acid type (HCl vs. H2SO4) on membrane fouling and cleaning as well as permeate flux and quality during the processing of swine wastewater with a spiral-wound RO membrane was investigated. The use of H2SO4 to lower pH produced slightly higher permeate fluxes than HCl and there was no indication of sulfate precipitates on the membrane. Membrane fouling intensity and flux recovery upon cleaning were not affected by pH level or acid type. Lowering swine wastewater pH from 7.1 to 6.5 with HCl reduced TAN concentration in permeate from 142 to 59 mg/L. Using H2SO4 to lower pH to 6.5 further decreased TAN concentration to 39 mg/L. At pH 6.5 with both acid types, the concentration of unionized NH3 in the permeate was below the Canadian guideline of 0.019 mg/L for the release of wastewater to an aquatic environment. The use of H2SO4 would be recommended with swine wastewater, because of lower cost and volumetric input required to lower pH, as well as higher permeate quality and flux.

Assessment of a rainwater harvesting system for pollutant mitigation at a commercial location in Raleigh, NC, USA

Low Impact Development (LID) and Water Sensitive Urban Design have as one of their tenets the use of rainwater harvesting (RWH) systems to provide water for use on site. Historically implemented in arid or semi-arid regions, RWH has recently surged in popularity in more humid regions, such as the southeastern USA, due to increased interest in water conservation during severe drought conditions. An LID commercial site in Raleigh, NC, incorporated RWH with other stormwater control measures to mitigate runoff quantity and improve runoff quality. A 57,900-liter RWH tank used for landscape irrigation was monitored to determine influent and effluent water quality. Samples were analyzed for total nitrogen, total phosphorus, total Kjeldahl nitrogen (TKN), total ammoniacal nitrogen (TAN), nitrite-nitrate (NOX), orthophosphate (Ortho-P) and total suspended solids (TSS). Low concentrations were observed for all pollutants monitored; for example, influent and effluent TP concentrations were 0.02 and 0.03 mg/L, respectively. Statistical testing showed significant increases in TAN and organic nitrogen (ON) concentrations by 33 and 38%, respectively, from inflow to outflow. NOX and TSS concentrations decreased significantly by 23 and 55%, respectively. Concentrations of all other pollutants were not significantly different between the inflow and outflow. Influent concentrations to the RWH tank were less than previously published rainfall pollutant concentrations, indicating potentially irreducible concentrations onsite. While a single case study, this RWH system appears to offer some pollutant mitigation, especially for TSS.

Total ammoniacal nitrogen biofiltration of wastewaters from aquaculture systems using Macrocystis spp.

The results of total ammoniacal nitrogen (NH3 + NH4 +) removal in aquaculture systems using two experimental sets, aquatic seedlings produced in laboratory controlled conditions and wild seaweed (Macrocystis spp.) in reproductive state, are shown in this work. Biofiltration assays were carried out using a load of total ammoniacal nitrogen (TAN) of 1 mg/L. Absorption rates were measured taking into account a previous surface characterization, which gave values of 44 ± 14 cm2/g and 18 ± 6 cm2/g for aquatic seedlings and wild algae, respectively. The following parameters were measured during the experimental runs: temperature, pH, O2, illuminance or light intensity, salinity and total solids. TAN removals of 61% and 70% were achieved for the seedlings and Macrocystis spp., respectively, after 17 h of treatment. The TAN absorption results were expressed as a function of surface and mass achieving the following values: 3.0 nmol N cm−2 h−1 and 111 nmol N g−1 h−1 for the seedlings, and 6.9 nmol N cm−2 h−1 and 122.4 nmol N g−1 h−1 for the macroalgae. In the light of these biofiltration processes, the initial TAN concentration decreased by 90% for the seedlings and wild algae over approximately 110 and 41 h, respectively. In addition, TAN removals achieved with Macrocystis spp. were always higher than those obtained with aquatic seedlings for the same operating periods.

Co-digestion of source segregated domestic food waste to improve process stability

Cattle slurry and card packaging were used to improve the operational stability of food waste digestion, with the aim of reducing digestate total ammoniacal nitrogen concentrations compared to food waste only. Use of cattle slurry could have major environmental benefits through reducing greenhouse gas emissions associated with current management practices; whilst card packaging is closely linked to food waste and could be co-collected as a source segregated material. Both options increase the renewable energy potential whilst retaining organic matter and nutrients for soil replenishment. Co-digestion allowed higher organic loadings and gave a more stable process. A high ammonia inoculum acclimated more readily to cattle slurry than card packaging, probably through supplementation by trace elements and micro-organisms. Long-term operation at a 75-litre scale showed a characteristic pattern of volatile fatty acid accumulation in mono-digestion of food waste, and allowed performance parameters to be determined for the co-digestion substrates.

Technical Note: Feasibility of Extracting Ammonia from Broiler Litter and Scale-Up Considerations

Air inside the broiler litter bed has high ammonia concentrations. The feasibility of extracting ammonia from the broiler litter bed for use as a fertilizer was investigated. Suction was applied to six -in. (12.7-mm) CPVC pipes with perforations placed 0.15 m below the litter surface in a pen stocked with 150 birds. Litter air was pulled into a phosphoric acid reactor where the ammonia was converted to ammonium phosphate, a fertilizer. Over 51 d, 72.6 g of ammonia was recovered and the pipes did not clog. Ammonia recovery could have been higher had litter ammonia concentrations been comparable with commercial broiler houses. Ammonia removal from the pen did not impact ammonia concentrations above the litter or bird performance. Placing the pipes close to the litter surface where total ammoniacal nitrogen concentrations would have been higher due to fecal loading may have reduced ammonia concentrations in the pen. Litter moisture content was reduced by the ammonia extraction system. A modified scaled-up system may be technically feasible but not cost-effective. Economic feasibility of the system can be improved if pipes placed closer to the surface improve bird performance by reducing in-house ammonia concentrations.

Concentration of ammoniacal nitrogen in effluent from wet scrubbers using reverse osmosis membrane

Sulphuric acid is commonly used in acid scrubbers as a highly efficient ammonia trap and results in the production of ammonium sulphate. The disposal of the large amount of effluent produced from an acid scrubber is one of the major issues that limit its application. Two reverse osmosis membranes were tested for their effectiveness in concentrating the ammoniacal nitrogen, which can be used as a fertiliser, from acid scrubber effluent. The permeate flux was substantially affected by membrane type, feeding total ammoniacal nitrogen (TAN) concentration, applied pressure, and feeding flow rate. However, TAN retention was only significantly affected by membrane type. The highest TAN retention of 98.1% was achieved with the SG membrane at a feeding TAN concentration of 6.4 g l−1, applied pressure of 5.5 MPa, and feeding flow rate of 3.1 l min−1.