Biografi

Fasil Ejigu Eregno has over eight years of the development project, research and university teaching experience. Currently, he is working as a research scientist in the Department of Urban Greening and Environmental Engineering, Norwegian Institute of Bioeconomy Research (NIBIO). He received his PhD in Water and Environmental Engineering from the Faculty of Science and Technology (RealTek), Norwegian University of Life Sciences (NMBU), Norway. He has a multidisciplinary academic background and proficient in water quality analysis and modelling, hydrological modelling, decentralised wastewater treatment systems, chemical-microbial health risk assessment. He has an interest in working with water quality analysis and modelling for municipal water services (drinking water, wastewater, stormwater and recreational water) framed around minimal emission of chemical and microbial pollutants, and integrate with chemical-microbial risk assessment (C-MRA) framework to identify management targets for improved eco-health and living conditions.

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Sammendrag

The transmission of pathogens from partially or fully treated wastewater to different water sources are a pervasive risk to public health. To reduce the risk, the integration of source separation, on-site greywater treatment system, and an efficient disposal scheme are the most critical approaches. This study intended to evaluate the removal of nutrient and microbial suspension in the filtration systems used for effluent disposal. The effluent from an on-site greywater treatment plant was loaded into the columns, and the effluent from the columns was monitored for nutrients, total coliform bacteria, Escherichia coli, and Salmonella typhimurium phage 28B (St28B) for one year. Thus, from the range of infiltration systems tested, column-B (15 cm layer of each, Filtralite, fine sand, and till soil) showed the highest removal of total coliforms and E. coli, 3–4 log10 reduction, while the lowest removal observed in column-C (a layer of 25 cm crushed stone and 50 cm till soil), 2–3 log10 reduction. The virus removal efficiency of the columns reduced from 19% to 70% during the simulation of a rainfall event. Moreover, the rise of St28B concentration after rainfall experiment may probably the sign of detachment enhanced by low ionic strength rainwater.

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Sammendrag

Denne rapporten er skrevet på oppdrag fra Bergen kommune i forbindelse med prosjektet «Forurensingsanalyse av drikkevannskilden Jordalsvatnet med vanntilsigsområde». Prosjektet er gjennomført i samarbeid mellom NIBIO, NMBU og SINTEF. Vi har sett på næringsstofftilførsler, algesammensetning, sykdomsfremkallende mikroorganismer, gjeldende restriksjoner og hygieniske barrierer. Hovedutfordringen antas å være økt algemengde og naturlig organisk materiale i råvannskilden, samt næringsstofftilførsler fra Indrevatnet. Det har av det blitt utarbeidet forslag til tiltak for å redusere tilførsler av fosfor fra nedbørfeltet til Indrevatnet. Vi anbefaler også at det gjøres en vurdering av fryse/tine effekter med hensyn til eventuelle lekkasjer fra avløpsledninger, samt en oppfølging av anbefalinger til utvidede klausuleringsbestemmelser som tidligere er gitt av Rådgivende Biologer AS.........