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Learning objective : to become familiar with basic functions of various physical, chemical and biological processes. Physical ~ screening and filtration,

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Presentation on theme: "Learning objective : to become familiar with basic functions of various physical, chemical and biological processes. Physical ~ screening and filtration,"— Presentation transcript:

1 Learning objective : to become familiar with basic functions of various physical, chemical and biological processes. Physical ~ screening and filtration, sedimentation, flotation C hemical ~ coagultation/flocculation, adsorption, precipitation, UV-radiation Biological ~ microbial decomposition, predation, uptake in plants 4.6 Physical, biological and chemical treatment processes What compounds can be removed from wastewater? How can Nature assist or react?

2 Treatment results for small and large water utilities More than 2,000 persons Less than 2,000 persons J-O Drangert, Linköping University, Sweden

3 B: Physical processes Possible combinations of physical processes Jan-Olof Drangert, Linköping university, Sweden screeningforced micro- filtration flotation and sedimentation

4 Screening of debris and other solid items Solids trapped by a screen in a city wastewater treatment plant Organics from kitchen pipe sorted out in a plastic screen Jan-Olof Drangert, Linköping university, Sweden

5 Flotation and sedimentation processes Inlet of wastewater Baffels Outlet of treated water Inspection hole Floating grease, particles, organisms Jan-Olof Drangert, Linköping university, Sweden Sludge built up

6 Filtration – mainly by gravity Saturated flow of wastewater Partially unsaturated flow Jan-Olof Drangert, Linköping university, Sweden

7 Forced micro-filtration Manufactured porous material Direction of filtered water flow Applied pressure Jan-Olof Drangert, Linköping university, Sweden

8 C: Chemical processes Adsorption of charged particles G. Jacks, Royal Institute of Technology, Stockholm OH H 2 PO Fe OH H 2 PO Al OH Adsorption of phosphate on ferric hydroxide Adsorption of phosphate on aluminium hydroxide particles

9 The three important kinds of charged soil particles are : 1.Organic matter RCOOH RCOO - + H + (a negative pH-dependent charge) R is phenolic ring derived from lignite in residues of plants 2. Clay minerals Clay mineral consist of Al-Si-sheets with different cations (Na +, K + etc.) in between the sheets. There is a negative charge on sides and edges: 3. Ferric hydroxides Fe(OH) 3 Fe(OH) 2- + H + (a pH-dependent positive charge) R-COO - Pb 2+ R-COO - Organic overcoat on a soil mineral - - K + K + Mg Cu 2+ OH Fe(III) + HAsO 4 - OH Adsorption of charged particles to soil medium G Jacks, Royal Institute of Technology, Stockholm Mineral grain

10 Adsorption of chemical compounds differ Copper (Cu) and Zink (Zn) are positively charged, and adsorb easily on organic matter and clays when the pH > 7 Arsenic (As) is negatively charged and adsorbs easily on ferric hydroxides when pH < 7 G Jacks, Royal Institute of Technology, Stockholm

11 Precipitation – a chemical reaction between dissolved compounds to form solids Flocculation - an aggregation process (or processes) leading to the formation of larger particles from smaller particles G. Jacks, Royal Institute of Technology, Stockholm Precipitation and flocculation

12 Source: Ubomba-Jaswa et al TheMethod.htm UV-radiation by sunlight Inactivation of micro- organisms by UVA- radiation and increased temperature

13 More diffuse stratification Strong algal stratification K Tonderski, Linköping University Sweden Courtesy of Duncan Mara, University of Leeds, UK Vertical view of the pond Shallow ponds with a dense population of algae

14 Ozonation and chlorination

15 D: Biological processes Karin Tonderski, Linköping university, Sweden

16 Biological processes - with air Oxygen is vital for most living organisms, including bacteria and viruses. When oxygen is present, organic matter (measured as BOD) is efficiently decomposed by organisms into CO 2 + water: + oxygen Unsaturated soil profile Aerobic bacteria Jan-Olof Drangert, Linköping university, Sweden Organic matter

17 Biological processes - without air Many microorganisms can survive in environments with no oxygen and they use other compounds for their survival: + e.g. nitrate, sulphate or iron ions ( Fe 3+ ) Organic matter in waste- water CO 2 + e.g. N 2, S 2-, Fe 2+ Saturated soil profile with little or no oxygen Anaerobic micro- organisms Jan-Olof Drangert, Linköping university, Sweden

18 Microorganisms attached to surfaces are more stable than those suspended in water Grain particle Jan-Olof Drangert, Linköping university, Sweden

19 O 2 H 2 O (oxygenisation) NO 3 - N 2, N 2 O (denitrification) MnO 2 Mn 2+ Fe(OH) 3 Fe 2+ SO 4 2- H 2 S (sulphate-reduction) CO 2 CH 4 (methanogenesis) When microorganisms descend the redox-ladder they first use O 2 as an electron acceptor, then nitrate NO 3, and further down other compounds as electron acceptors. The blue arrow indicates a reaction with energy-rich organic substances (electron donors) in the wastewater Gunnar Jacks, Royal Institute of Technology, Stockholm Redox-ladder Decrease in oxygen

20 Gunnar Jacks, Royal Institute of Technology, Stockholm Changes in concentrations of electron acceptors when organic matter (TOC) decomposes

21 What happens in the root zone? O 2, sugars, proteins, etc Jan-Olof Drangert, Linköping university, Sweden Water, nutrients, heavy metals, gases (e.g. CO 2 ) Organic matter, O 2, NO 3 -, SO 4 2-, CO 2 etc

22 Predation on microorganisms stimulates decomposition Courtesy of Frida Lögdberg, Linköping university

23 Soil organisms vary tremendously in size and numbers Modified from Sylvia, D. et al Principles and applications of soil microbiology A teaspoon soil ~ one gram

24 Organic matter is decomposed most efficiently in the top soil Million organisms per gram soil 10 6 Depth in meter Anaerobic bacteriaAerobic bacteria 0.5 m Courtesy of G. Jacks, Royal Institute of Technology, Stockholm Soil surface 0


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