Nitrification in Aquarium 2 (Lab Journal)

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This is the detailed lab journal of the Nitrification in Aquarium 2 experiment. For a structured summary, please refer to the report of the experiment.

General comments

The aquariophilic kits and pH strips we use are color-based indicators, and can be quite imprecise. The small variations of concentration can be considered as insignificant.

Day 0 - 12/08/2015 - 22h

We started the NA2 experiment on this day.

Culture

We started the culture for NA2 from 15 l of the mix from NA1.

Recalling the main concentrations for NA1 culture at 7 pm :

  • pH = 7.4
  • Ammonium concentration = 1.5 mgN/l
  • Nitrate concentration = 20 mgN/l
  • Nitrite concentration = 0.8 mgN/l

However, we measured different values when measuring in our new “bioreactor”

  • pH = 7.4 (stable)
  • Ammonium concentration = 3 mgN/l
  • Nitrate concentration = 10 mgN/l
  • Nitrite concentration = 0.8 mgN/l

(We took out 30 ml of culture for analysis purposes.)

This difference in our measurements most probably comes from the inaccuracy of our analysis kits.

Bioreactor

This culture was poured in a 20 L bucket , in which a pump (the one used for NA1) was dripping 380l/h of air through two diffusers.

Urine

We fed the culture with 25 ml of urine, from the batch started on August 12th.

The pH of urine slightly increased to 7.2, urea hydroloysis has probably not happened yet.

Day 1 - 13/08/2015 - 16h

Culture

We took out 35 ml of culture for analysis purposes.

The measured pH of the culture was 7.4 (stable).

We measured a stable ammonium concentration of 3 mgN/l.

We measured a stable nitrate concentration of 10 mgN/l.

We measured a stable nitrite concentration of 0.8 mgN/l.

Urine

We fed the culture with 25 ml of urine, from the batch started on August 12th.

The pH of urine was measured at 7.2 (stable), urea hydroloysis has probably not happened yet.

Day 2 - 14/08/2015 - 12h30

Culture

We took out 35 ml of culture for analysis purposes.

The measured pH of the culture was 7.4 (stable).

We measured a slightly increasing ammonium concentration of 5 mgN/l.

We measured a sloghtly decreasing nitrate concentration of 6 mgN/l.

We measured a slightly increasing nitrite concentration of 1 mgN/l.

Urine

We fed the culture with 25 ml of urine, from the batch started on August 12th.

The pH of urine was measured at 7.4 (slightly increasing), urea hydroloysis has probably not happened yet.

20h30

Culture

We took out 70 ml of culture for analysis purposes.

We think that ammonia may be evaporating, and that the amount of ammonia evaporated may be increased by increased aeration. We therefore decided to measure ammonium concentration again a few hours after feeding the system with urine.

In eight hours, we observed a slight decrease in ammonium concentration to 3 mgN/l (-2 mgN/l). This may indicate an evaporation of ammonia, but the measurement error margins being quite large, we cannot be certain.

Urine

We fed the culture with 40 ml of urine, from the batch started on August 12th.

Day 5 - 17/08/2015 - 19h

Culture

We took out 70 ml of culture for analysis purposes.

We measured a slightly increasing ammonium concentration of 5 mgN/l.

We measured a drastically increasing nitrate concentration of 80 mgN/l.

We measured an increasing nitrite concentration of 10 mgN/l.

Urine

We fed the culture with 65 ml of urine, from the batch started on August 12th.

The pH of urine was measured at 7.4 (stable), urea hydroloysis has probably not happened yet.

Day 6 - 18/08/2015 - 21h

Culture

We took out 25 ml of culture for analysis purposes.

The measured pH of the culture was 7.4 (stable).

We measured a stable ammonium concentration of 5 mgN/l.

We measured a stable nitrate concentration of 80 mgN/l.

We measured a stable nitrite concentration of 10 mgN/l.

Urine

No urine was fed to the culture, as the nitrite level stayed high.

Day 7 - 19/08/2015 - 15h

Culture

We took out 20 ml of culture for analysis purposes.

We measured a stable ammonium concentration of 5 mgN/l.

We measured a drastically increasing nitrate concentration of 160 mgN/l.

We measured a slightly decreasing nitrite concentration of 9 mgN/l.

The level of the culture surface got about 3 cm lower overnight.

Urine

As the culture seems to consume ammonium, we fed the culture with 65 ml of urine, from the batch started on August 12th.

The pH of urine was measured at 7.7 (slightly increasing), urea hydroloysis may be happening.

Day 9 - 21/08/2015 - 15h30

Culture

We took out 30 ml of culture for analysis purposes.

The measured pH of the culture was 7.1 (stable).

We measured a slightly decreasing ammonium concentration of 4.5 mgN/l.

We measured a stable nitrate concentration of 160 mgN/l.

We measured an increasing nitrite concentration of 16 mgN/l.

We ended the experiment at that stage.