Nitrification in Aquarium 3 (Lab Journal)

This is the detailed lab journal of the Nitrification in Aquarium 3 experiment. For a structured summary, please refer to the report of the experiment.

Day 0 - 12/08/2015 - 22h

We started the NA3 experiment on this day.

Culture

We started the culture for NA3 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 = 7.2 - Ammonium concentration = 3 mgN/l - Nitrate concentration = 10 mgN/l - Nitrite concentration = 0.7 mgN/l

(We took out 35 ml of culture for analysis purposes.)

This difference in theses 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 (comparable to the one used for NA1) was dripping air through two diffusers.

Urine

We fed the culture with 500 ml of urine, from the batch started on August 12th.

A strong smell of urine stays after feeding.

Day 1 - 13/08/2015 - 16h

Culture

We took out 30 ml of culture for analysis purposes.

The measured pH of the culture was 7.4 (slightly increasing).

We measured an increasing ammonium concentration of 8 mgN/l.

We measured a slightly decreasing nitrate concentration of 8 mgN/l.

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

Urine

We fed the culture with 500 ml of urine, from the batch started on August 12th.

We can still smell urine after feeding the culture.

19h30

We added 15 ml of an aquariophilic concentrated nitrifyers culture (10x recommended dose), in order to see if launching a thriving culture helps to increase nitrate concentration.

Day 2 - 14/08/2015 - 12h30

Culture

We took out 20 ml of culture for analysis purposes.

The measured pH of the culture was 7.5 (slightly increasing).

We measured a decreasing ammonium concentration of 2 mgN/l.

We measured an increasing nitrate concentration of 20 mgN/l.

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

Urine

We fed the culture with 500 ml of urine, from the batch started on August 12th.

19h30

Culture

We took out 70 ml of culture for analysis purposes.

The measured pH of the culture was 7.8 (slightly increasing).

We think that ammonia may be evaporating because of aeration. We therefore decided to measure ammonium concentration again a few hours after feeding the system with urine.

We observed an ammonium concentration of 10 mgN/l. This is quite high, but not so high compared to the fact that we fed the culture with 500 ml of urine (supposed concentration of 4k-5k mgN/l) only seven hours earlier. This may indicate an evaporation of ammonia

Day 5 - 17/08/2015 - 19h

Culture

We took out 70 ml of culture for analysis purposes.

The measured pH of the culture was 8.4 (increasing).

We measured an increasing ammonium concentration of 30-60 mgN/l. This may indicate a slow urea hydrolysis, slightly converting urea into ammonium.

We measured an imprecise nitrate concentration, in the range of 2-20 mgN/l.

Urine

The increase in ammonium concentration suggests that nitrogen may be accumulating in the culture in the form of urea, which would be hydrolysed only slowly. To avoid an excessively high concentration of ammonium, leading to a potentially toxic concentration of nitrite, no urine was fed to the culture today.

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

No urine smell detected.

Day 6 - 18/08/2015 - 21h

Culture

We took out 20 ml of culture for analysis purposes.

The measured pH of the culture was 8.5 (increasing).

We measured a drastically decreasing ammonium concentration of 0.5 mgN/l.

We measured a nitrate concentration of 6 mgN/l.

We measured a slightly increasing nitrite concentration of 2 mgN/l.

Urine

We fed the culture with 500 ml of urine, from the batch started on August 12th.

The pH of urine was measured at 7.4-7.7, urea hydroloysis may be starting.

Low urine smell detected.

Day 7 - 19/08/2015 - 15h

Culture

We took out 25 ml of culture for analysis purposes. We also took out 1 l of culture to compensate the volume of urine added, and avoid overflow from our 20 l bioreactor.

The measured pH of the culture was 8.5 (stable).

We measured a drastically increasing ammonium concentration of 50 mgN/l.

We measured an increasing nitrate concentration of 20 mgN/l.

We measured a stable nitrite concentration of 2 mgN/l.

Urine

We fed the culture with 500 ml of urine, from the batch started on August 12th.

The pH of urine was measured at 7.7, urea hydroloysis may be starting.

Low urine smell detected.

Day 9 - 21/08/2015 - 15h30

Culture

We took out 30 ml of culture for analysis purposes.

The pH of the culture reached its highest point at 8.9.

The ammonium concentration remains high, around 50-150 mgN/l.

Nitrate concentration decreased to 8 mgN/l.

Nitrite concentration decreased to 1 mgN/l.

The decrease of nitrate and nitrite concentration may be due to the removal of culture and addition of urine in the context of a quite unstable microbial culture.

Urine

The culture was not fed with urine, as the ammonium concentration is still quite high.

The pH of urine was measured at 8.5, urea hydroloysis has probably happened.

Low urine smell detected.

The experiment was terminated that night.