The influence of the nitrate load on the denitrification capacity
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Typ
Examensarbete på grundnivå
Program
Publicerad
2011
Författare
Eriksson, Jenny
Modellbyggare
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Sammanfattning
Gryaab AB, which runs the Rya plant in Gothenburg has expanded its wastewater treatment plant with a new nitrogen and phosphorus removal facility, this in order to achieve the new target values concerning emissions of nitrogen and phosphorus. The new conditions is 0.3 mg/l phosphorus and 10 mg/l nitrogen in the effluent per calendar year. The new nitrogen removal is a post-denitrification plant where bacterias are growing in suspended carriers, so called MBBR-technology. Since this type of biological treatment technology is relatively new there is not so much knowledge about how to operate it to obtain the most effective capacity. The post-denitrification plant at the Rya has six denitrification lines, each line consists of three reactor zones. First zone is designed to be used both as a nitrification- and denitrifikation zone. The thesis aims to study how different nitrate load affects the denitrification capacity. The method for studying the capacity is based on having a test line with low nitrate (NO3) load, 85 NO3 kg / day and a reference line with a high nitrate load, 288 NO3 kg / day. A flow control is used to give a constant nitrate load to the line by regulating the flow of the incoming nitrate concentration.. Denitrification tests are performed to study the changes in the capacity when the nitrate load is altered. The tests are designed to to simulate the condition in the full-scale plant, i.e. oxygen free environment and the carriers under constant suspension. The tests shows the denitrification rate of the bacteria in the postdenitrification plant, and thus the denitrification capacity. During 10 weeks the denitrification in the post-denitrification plant were studied. The first experimental period the test-line had low nitrate load, followed by a period in which the test-line had high nitrate load, and finally a period in which the nitrate load was again low. The reference line had during the study high nitrate load, 288 NO3 kg/day. The results show that at low nitrate load the capacity diminishes for 13-14 days and then stabilizes. Repeatability at low nitrate load exists and with a nitrate load of 85 kg NO3 / day the capacity stabilizes at approximately 1,1- 1,3 gN/m2/d. In the study with high nitrate load, 288 NO3 kg/day the capacity has already increased after 9 days from about 1,1 to 1,8 gN/m2/d gN/m2/d. The highest denitrification capacity value observed was 2,2 gN/m2/d.
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Ämne/nyckelord
Kemi , Chemical Sciences