Nitrate aquarium

This experiment describes a semester-long project in which the concentration of several ions in a fresh water aquarium are monitored. Ions that are monitored using potentiometric electrodes include H+ (pH electrode), Gh (chloride electrode), HG03 (GO2 electrode), NH4+ (NH3 electrode), and N03 (NH3 electrode). Nitrate concentrations were determined following its conversion to ammonia. 

R/0 unit Reverse Osmosis Unit for water purification in small aquariums and miniature yard-ponds, utilizes a membrane under pressure to filter dissolved solids and pollutants from the water. Two different filter membranes can be used the CTA (cellulose triacetate) membrane is less expensive, but only works with chlorinated water and removes 50-70% of nitrates, and the TFC membrane, which is more expensive, removes 95% of nitrates, but is ruined by chlorine. R/0 wastes water and a system that cleans 100 gallons a day will cost ft-om 400 to 600 with membrane replacement adding to the cost. A unit that handles 140 gallons a day will cost above 700,00. 

Managing a salt-water aquarium. A tank at the New Jersey State Aquarium has a volume of 2.9 million liters.7 Bacteria are used to remove nitrate that would otherwise build up to toxic levels. Aquarium water is first pumped into a 2 700-L deaeration tank containing bacteria that consume 02 in the presence of added methanol ... 

Students at Harvey Mudd College monitor a saltwater aquarium to study the chemistry of a marine ecosystem. When fish and food are introduced into the aquarium on day 0 in panel a, organic compounds are metabolized to produce NH3. Anunonia is toxic to marine animals when the level exceeds 1 ppm but, fortunately, it is removed by Nitrosomonas bacteria, which colonize the aquarium filter and oxidize NH3 to nitrite (NO2). Alas, NO2 is also toxic at levels above 1 ppm, but it is further oxidized to nitrate (NO J) by a second colonization of Nitrobacter bacteria. The natural process of oxidation of NH3 to NO2 and NOJ is called nitrification. 

Box 6-1 stated that nitrogen compounds derived from animals and plants are broken down to ammonia hetm>trophic bacteria. Ammonia is oxidized first to nitrite 02 ) and then to nitrate (NO J) by nitrifying bacteria. In Section 6-3 we saw how a permanganate titration was used to standardize a nitrite stock solution. The nitrite solution is used here to pr xue standards for a spectrophotometric analysis of nitrite in aquarium water. 

Excess NADH is then oxidized to NAD to eliminate interference with color development when NO2 from Reaction 18-9 is measured colorimetrically by reactions such as 18-7. For quantitative analysis in the field, a small, battery-operated spectrophotometer can be used with a set of nitrate standards. Alternatively, color can be compared visually with a chart showing colors from several standards. Commercial field kits allow analysis in the range 0.05-10 ppm nitrate nitrogen. Laboratory apparatus provides a precision of 2% when measuring 0.2 ppm NO3 nitrogen, with a detection limit of 3 ppb. Nitrate reductase has been applied to the measurement of nitrate in a classroom aquarium. ... 

Figure 23-15 Measurement of nitrate in aquarium water (Box 6-1) by capillary electrophoresis. At the detection wavelength of 222 nm, many species in the water have too little absorbance to be observed, (a) Standard mixture containing 15 pig/mL nitrate (NO3),... 

From Figure 23-15, estimate the concentration of nitrate in the aquarium water. Aquarium water was diluted from 1 mL to 100 mL, and the final solution contains the same 10 ppm of internal standard IO4 as in the standard mixture. For an estimate, use peak height instead of peak area. There is no need to use normalized peak area = peak area/migration time because migration times are nearly the same in both electropherograms. 

A water-gel explosive called WGE-1 consists of approximately 46 wt% ammonium nitrate, 24 wt% TNT, 15 wt% sodium nitrate, 13.2 wt% water, 1.2 wt% ethylene glycol, and 0.6 wt% thickener) and has a density of 1.5 g/cc. In a 20 cm diameter charge, the detonation speed is 0.481 cm//rsec as described in reference 33. This is well below the BKW ideal detonation speed of 0.73 cm/nsec and C-J pressure of 187 kbar. A BKW calculation, under the assumption that no ammonium nitrate reacts, gives a velocity of 0.495 cm/ijLsec and a pressure of 71 kbar. The aquarium test data could be reproduced for WGE-1 with no ammonium nitrate reacting at the C-J plane and all the ammonium nitrate remaining inert behind the detonation wave. 

Detonation performance tests have been performed for many ammonium salts containing propellants and explosives. Some of the propellants and commercial explosives that have been examined and the nature of their nonideality are summarized in Table 2.5. The first two explosives in the table are common commercial explosives. Aquarium tests were performed for both explosives. To reproduce the observed performance, all of the ammonium nitrate and some of the aluminum had to be treated as inert. The aquarium test for the first commercial explosive required no additional reaction of the ammonium nitrate behind the C-J state. The aquarium test for the second commercial explosive required some additional reaction of the aluminum or ammonium nitrate below the C-J state. The ammonium perchlorate containing systems in Table 2.5 are various propellants. As the amount of ammonium perchlorate is increased in the propellants with corresponding decrease in HMX, the degree of nonideality increases. The propellant with 36% ammonium perchlorate also had the air isentrope state determined. The measured air isentrope particle velocity was 0.6 cm/ sec and 0.6 kbar, which is in agreement with the isentrope for all the ammonium nitrate remaining inert. 

Using BKW one can program additional reaction of the remaining ammonium nitrate along the isentrope to approximate the additional energy release that the aquarium data requires. Several rates of additional ammonium nitrate reaction were therefore programmed into BKW and the isentropes were used to calculate the position of the interface and water shock. Several of the rates could reproduce the observations one such rate is shown in Figure 2.18. The observed detonation velocity of about 0.35 cm/)usec can be reproduced if 55% of the ammonium nitrate is assumed to not react at the C-J point. 

The air isentrope state for 10-cm-diameter ANFO was measured and is shown in Figure 2.20, along with three release isentropes for ANFO corresponding to complete reaction, 55% inert ammonium nitrate with no additional burn, and 55% inert ammonium nitrate with additional burn to completion. The air isentrope data are in good agreement with the assumption of 45% reaction at the C-J plane followed by additional burn to completion that was required to describe the aquarium data. 

Aquarium tests were also performed for a 15-cm and a 20-cm-diameter ANFO charge in clay pipe surrounded by water. The measured detonation velocities and partially reacted ammonium nitrate interpretations obtained from the aquarium tests follow. 

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