Production and Utilization of Municipal Wastewater Sludges
Laaksonen, Petteri Matti Eemil (2011)
Laaksonen, Petteri Matti Eemil
2011
Ympäristö- ja energiatekniikan koulutusohjelma
Luonnontieteiden ja ympäristötekniikan tiedekunta - Faculty of Science and Environmental Engineering
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Hyväksymispäivämäärä
2011-09-07
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-2011091614806
https://urn.fi/URN:NBN:fi:tty-2011091614806
Tiivistelmä
Present wastewater treatment processes, among which the activated sludge process is the most widely used, produce massive volumes of excess sludge that requires proper treatment. Excess sludge typically consists of feasible organic substances such as enzymes and proteins, and can offer many beneficial utilization possibilities. Thus, it is reasonable that in addition to being perceived as bare waste, new techniques and methods for sludge utilization and disposal are being constantly studied. Recent concerns on the climate change and depletion of mineral oil have awakened interest on recovering the lipids from the excess sludge. Techniques for converting the sludge into biodiesel exist, but the current technology is not economically feasible. Thus, novel and more cost effective techniques are being developed. One possibility is to combine biological wastewater treatment and enhanced production of lipid rich sludge.
The main goal of this thesis was to study if microbial lipid accumulation in municipal wastewater treatment plant’s sludge could be enhanced by manipulating the carbon to nitrogen ratio (C/N ratio). Experiments were conducted using batch bottle cultivations, and the C/N ratio was manipulated by adding glucose. With initial glucose addition, the lipid content (mass-% of dried sludge) and concentration (mg lipids/L cultivation) increased from initial in three out of four batch bottle experiments. The highest lipid content (9.2 mass-% compared to initial 6.3 mass-%) was achieved with initial glucose addition of 4 g/L. The highest lipid concentration (570 mg/L compared to initial 516 mg/L) was achieved with initial glucose addition of 10 g/L. In addition, over 100 mg/L increases in lipid concentration were detected with initial glucose addition of 10 g/L in both activated sludge and excess sludge experiments.
In addition to batch bottle experiments, a laboratory scale activated sludge reactor was constructed mainly for gathering useful insight into future experiments. Sludge and lipid production was studied using municipal wastewater as an influent. In order to simulate different organic loadings, glucose was added to the influent wastewater. With higher organic loadings, slightly higher lipid content (mass-% of dried sludge) was achieved compared to initial. Sludge’s lipid concentration (mg/L) was lower because of the decreased concentration of suspended solids in the laboratory scale reactor. /Kir11
The main goal of this thesis was to study if microbial lipid accumulation in municipal wastewater treatment plant’s sludge could be enhanced by manipulating the carbon to nitrogen ratio (C/N ratio). Experiments were conducted using batch bottle cultivations, and the C/N ratio was manipulated by adding glucose. With initial glucose addition, the lipid content (mass-% of dried sludge) and concentration (mg lipids/L cultivation) increased from initial in three out of four batch bottle experiments. The highest lipid content (9.2 mass-% compared to initial 6.3 mass-%) was achieved with initial glucose addition of 4 g/L. The highest lipid concentration (570 mg/L compared to initial 516 mg/L) was achieved with initial glucose addition of 10 g/L. In addition, over 100 mg/L increases in lipid concentration were detected with initial glucose addition of 10 g/L in both activated sludge and excess sludge experiments.
In addition to batch bottle experiments, a laboratory scale activated sludge reactor was constructed mainly for gathering useful insight into future experiments. Sludge and lipid production was studied using municipal wastewater as an influent. In order to simulate different organic loadings, glucose was added to the influent wastewater. With higher organic loadings, slightly higher lipid content (mass-% of dried sludge) was achieved compared to initial. Sludge’s lipid concentration (mg/L) was lower because of the decreased concentration of suspended solids in the laboratory scale reactor. /Kir11