Physical-Chemical Reactor Essay

3.1.1 Physical-chemical parameters

The temperature of the reactor was stable at about 30 (±5)°C. Immediately after filling the reactor the pH was 5.5 and after one day the pH increased to 6.3 due to the addition of methanogenic leachate of pH 7. Afterwards the pH decreased progressively from 6.2 to 5.5 during the first 200 days. After day 200, pH increased steadily up to 7.3 at day 400 and remained steady until the end of the experiment at day 700. Conductivity increased from 22mS cm-1 to 36mS cm-1 due to the dissolution of salts into the leachate. The conductivity reached its lowest level (9.5 mS cm-1) at day 700 and seemed to increase towards the end of the experiment (day 700). The dissolved oxygen was depleted during the first two weeks of operation reaching values that fluctuated between 0 and 0.1 mgO2 L-1

3.1.2 Biological parameters Production of biogas started slowly during the first 180 days of operation, where approximately 3 m3 of biogas were produced, mainly composed of CO2. However from day 180, the biogas production started to increase dramatically until day 500, in which period the biogas composition changed to 65%CH4 -

Ammonia levels decreased drastically within the period between day 400 and 430 to values in the range of 0.79g L-1 and remained constant the next 300 days. Finally, ammonia levels dropped in the last stage of the experiment to values around 0.6g L-1. No NO3-, NO2- or NH3 were detected on incidental measurements before day 350. However, NO3- was detected in minimal quantities (2 -5mg NO3-L-1) from day 350 up to an average of 30mg NO3-L-1 at the end of the experiment. Since the total Kjeldahl nitrogen (TKN) was composed of 75 - 80% ammonia, which was identical to a large extent of ammonia trend. Organic nitrogen was low and showed a decreased trend towards the end of the