Total Carbonate Carbon Research Articles

Modelling recovery of ammonium from urine by electro-concentration in a 3-chamber cell

Electro-concentration enables treatment and nutrient recovery from source-separated urine, and is a potential technology for on-site treatment using a 3 compartment configuration that has anode, cathode and middle concentrate compartments. There is a particular focus on driving concentration towards the precipitation threshold in the concentrate compartment to generate solid ammonium salts, including ammonium bicarbonate. To evaluate controlling mechanisms and the feasibility of achieving high concentrations, a dynamic mechanistic model was developed and validated using experiments with synthetic urine. It was identified that high concentrations are prevented by increased back diffusion (diffusion from the middle chamber to the anolyte and catholyte) due to large concentration gradients, and the preferential migration of protons or hydroxide ions due to a loss of buffering capacity in the anolyte and catholyte (due to pH extremes). Model-based sensitivity analysis also identified that electrolyte ion concentrations (including buffer capacity) were the main controlling mechanisms, rather than membrane or electrolyte current transfer capacity. To attain high concentrations, operation should be done using a) a high current density (however there is a maximum efficient current density); b) feed at short hydraulic retention time to ensure sufficient buffer capacity; and c) a feed high in ammonium and carbonate, not diluted, and not contaminated with other salts, such as pure ureolysed urine. Taking into account electron supply and bio-anodic buffer limitations, model testing shows at least double the aqueous concentrations observed in the experiments may be achieved by optimising simple process and operational parameters such as flow rate, current density and feed solution composition. Removal of total ammonium nitrogen (TAN) and total carbonate carbon (TCC) was between 43–57% and 39–53%, respectively. Balancing the sometimes conflicting process goals of high concentrations and removal percentage will need to be considered in further application. Future experimental work should be directed towards developing electrodes capable of higher current densities. In addition it would be desirable to use ion exchange membranes with higher resistance to water fluxes and which limit back diffusion. Future modelling work should describe osmotic and electro-osmotic water fluxes as a function of the concentration gradient across the membranes and ionic fluxes, respectively. More generalised wastewater physico-chemistry speciation models should identify best methods where relatively simple Davies activity corrections do not apply.

Omega-3 Fatty Acid Supplementation Affects Selected Phospholipids in Peripheral White Blood Cells and in Plasma of Full-Sized and Miniature Mares

Dietary omega-3 fatty acids (n-3 PUFA), notably eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), impart health benefits in humans and animals. In horses, dietary n-3 PUFAs elevate EPA and DHA and may promote anti-inflammatory effects. No reports document effects of dietary n-3 PUFA on fatty acyl components of circulating and cellular phospholipids in horses nor whether responses to dietary n-3 PUFA are similar among horse breeds. Ten Quarter Horse and 10 American Miniature Horse mares were assigned to n-3 PUFA (64.4 mg· kg body weight [BW]−1·d−1) or control diet for 56 days. Blood was sampled at 0, 28, and 56 days. Apparent phospholipid molecular species from several classes (phosphatidylcholine [PC]; “ether-linked” phosphatidylcholine [i.e., alk(en)yl, acyl glycerophosphocholine] [ePC]; phosphatidylethanolamine [PE]; phosphatidylinositol [PI]; and phosphatidylserine [PS]) were determined in plasma and peripheral blood mononuclear cells (PBMC) by mass spectrometry. Statistical analysis showed that six phospholipid species had diet × day interactions (P < .05) for both plasma and PBMC. Further evaluation of these species demonstrated that the mole percentage of PC(38:6), PC(40:7), PC(42:10), PE(38:5), PE(40:6), and PE(40:7) (where x:y represents total acyl carbon:total carbon-carbon double bonds) in both plasma and PBMC phospholipids was elevated in horses fed n-3 PUFA (P < .001 for all). Analysis of the acyl product ions revealed that these contained an acyl chain of mass consistent with an n-3 PUFA. Thus, supplementation increased n-3 PUFA in selected plasma and PBMC phospholipids. The absence of breed effects suggests that miniature and full-size horses responded similarly to dietary treatment.

Stable isotope geochemistry of organic matter alteration in Animikie Basin sediments within the thermal aureole of the Duluth Ccomplex

We have determined total organic carbon (TOC), total carbonate carbon (TCC), and δ 13C values for TOC in samples from the Early Proterozoic Animikie Basin sediments (Virginia and Biwabik Iron Formations) that have been variably metamorphosed by the Duluth Complex. TOC values for the variably metamorphosed Virginia Formation show no systematic variation with distance from the intrusion (TOC from 0.06 to 2.54%). In the Biwabik Iron Formation, samples outside the thermal aureole of the intrusion have TOC generally below 1% compared to 1.7–6.2% for samples within the thermal aureole. This enrichment may reflect extensive remobilization of organic carbon within the thermal aureole. However, δ 13C org values measured for both the Virginia and Biwabik Iron Formations within the thermal aureole are not significantly different from those outside the thermal aureole. It thus appears that, in the Iron Formation, the thermal shock caused by the intrusion induced migration of labile organic carbon that was isotopically similar to the residual kerogen. The relatively low TCC in samples within the thermal aureole of the intrusion appear to indicate decarbonation of the Iron Formation also occurred.

Determination of trace levels of total carbonate-carbon by indirect photometric ion chromatography with nitrogen purging

Purging with nitrogen substantially prevented atmospheric carbon dioxide from dissolving in the eluent used in indirect photometric ion chromatography. Total carbonate-carbon at trace levels could be determined as hydrogencarbonate by this method. By using an analytical column (250 × 4.6 mm I.D.) packed with MCI SCA-02 and 5.0 · 10 −4 M sodium hydrogenphthalate—1.5 · 10 −4 M N-2-hydroxyethyl-piperazine-N′-2-ethanesulphonic acid (HEPES) (pH 6.5) as the eluent, hydrogen-carbonate was detected as a negative peak at 250 nm. The detection limit (signal-to-noise ratio = 2) was 1.4 · 10 −11 mol (7 · 10 −7 M with an injection volume of 20 μl) and the calibration graph was linear from 3.0 · 10 −11 to 3.8 · 10 −9 mol ( r = 0.994). The coefficient of variation was less than 2% on injection of 4 · 10 −10 mol. Total carbonate-carbon at levels as low as 10 −4-10 −6 M level could be determined accurately. The errors in the analysis of practical samples by the method without nitrogen purging are demonstrated.