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The efficiency of the NIOO-KNAW proposed decentralized sanitation system in removal of Coliforms and Escherichia coli

how efficient is a 55 °C thermophilic UASB followed by an algae based photo bioreactor in removal of Coliforms and Escherichia coli

The efficiency of the NIOO-KNAW proposed decentralized sanitation system in removal of Coliforms and Escherichia coli

how efficient is a 55 °C thermophilic UASB followed by an algae based photo bioreactor in removal of Coliforms and Escherichia coli

Samenvatting

With increasing world population, more wastewater is produced which all need purification treatment. Removal of pathogenic organisms is important because they can cause problems to human health. This experiment will focus on the removal of human bacterial pathogens. The problem of human bacterial pathogens is that infections can emerge when there is contact between wastewater and humans. A bacterium is defined pathogenic when it causes disease to a human; therefore not all bacteria are pathogenic.In the Netherlands the water boards start cooperating together in order to conduct energy from the wastewater treatments instead of consuming energy for the treatment of wastewater. The demand for new sanitation systems developed several new techniques including a decentralized sanitation system. The Black Water (BW) of the Netherlands Institute of Ecology (NIOO KNAW) is highly concentrated waste water. The BW is treated in a 55 °C thermophilic up flow Anaerobic Sludge Blanket reactor (UASB). The BW from the NIOO-KNAW only consist of urine, faeces and 1 litre of groundwater flush. The effluent of the UASB is referred to as Digested Black Water (DBW). The NIOO-KNAW wants to use a thermophilic UASB operating at 55 °C because it is supposed that the pathogen removal is higher compared to a mesophilic UASB 20-42 °C due to higher temperatures. In the UASB mostly biological activity takes place and the organic carbons are converted into biogases including methane (CH4) which are collected and reused for heating up the UASB. The NIOO-KNAW does not has a UASB system operational and therefore 25 °C mesophilic effluent samples are derived from Sneek. Because the NIOO KNAW does not have a 55 °C thermophilic UASB in operation 55 °C thermophilic effluent is mimicked by incubating the 25 °Cmesophilic UASB at 55 °C for 4 days.The effluent of the UASB flows directly towards algea filled photo bioreactors(PBR). The algal filled PBR’s are used because of the bactericidal properties of algae. Therefore the NIOO-KNAW desires to implement an algal based photobioreactor. The algal specie inoculated in the PBR’s of the NIOO-KNAW is Chlorella sorokiniana, this species is commonly used in the scientific world because of broad growth spectrum. Identification of all the human pathogen bacteria species is expensive, therefore indicator species are used. The Total Coliform (TC) and the Escherichia coli (E. coli) bacteria are most commonly used as indicator species. The E. coli bacteria is most preferred as indicator species because this species is exclusively found in faeces and E. coli can outlive high temperatures and circumstances compared to other bacterial species. In the experiment there are three PBR’s filled with Chlorella sorokiniana. Each PBR present a different Hydraulic Retention Time (HRT), respectively 12 hours, 21 hours and 30 hours. The HRT is the variable for the removal of coliforms and E. coli’s. These HRT’s are based on the growth rate of Chlorella sorokiniana. The HRT times are based on the growth of the algae because the algae wash out with the effluent of the PBR.To detect TC and E. coli a culture plating technique is used. Three different mediums are selected: The m-Endo LES medium, the 1604 medium, and the 3M coliform/E-coli Petri films. The incubation time and temperatures are the samefor the 3 mediums, 35 °C± 0, 5 °C and the time is set at 24± 2 hours, for the 3M Petri film the coli forming units other than E. coli are counted after 24 hours incubation time, and on the same Petri film the E. coli after 48 hours of incubation time.According to the data the mimic 55 °C thermophilic UASB effluent still contain TC bacteria and E. coli bacteria. The results from the effluent of the PBR’s filled with Chlorella sorokiniana do not contain any E. coli bacteria, However, they do contain TC other than E.coli. The PBR with a HRT of 12 hours has the lowest amount of TC other than E. coli compared to the two other HRT’s. However, the effluent of the PBR with a HRT of 12 hours contains more TC than the effluent of the mimic thermophilic UASB. In the blank experiment only the 3M Petri films are used due to lack of time. The results was almost no growth at all. However it could be that the uv-light eliminated the bacteria because there were no algae to block the light. The overall conclusion is that the 55 °C thermophilic UASB could be efficient in removing TC and E. coli bacteria but more data is required. The PBR removes E. coli bacteria; however the algae enriches the effluent with TC growth. The amount of data is not sufficient enough to calculate approved statistical analyses. Although sufficient data is not available for approved statistical analyses, further data collection would make it possible to make a steady conclusion. With this data not a steady conclusion can be drawn, further investigation at this subject is necessary.

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OrganisatieVan Hall Larenstein
AfdelingMilieukunde
PartnersHogeschool Van Hall Larenstein
Netherlands Institute of Ecology
Datum2015-06-25
TypeBachelor
TaalEngels

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