MICROBIAL ECOLOGY_2023_24 LAAO-home slides3.pdf

Kwame Nkrumah University of Science & Technology, Kumasi, Ghana BIOL 252: MICROBIAL ECOLOGY 2023/2024 Name: Prof. (Mrs.)Linda Aurelia Ofori (PhD) Email: [email protected] /[email protected] Phone...

Kwame Nkrumah University of Science & Technology, Kumasi, Ghana BIOL 252: MICROBIAL ECOLOGY 2023/2024 Name: Prof. (Mrs.)Linda Aurelia Ofori (PhD) Email: [email protected] /[email protected] Phone Number: 0244220064  Water Treatment www.knust.edu.gh 7/15/24 2023/2024 1  www.knust.edu.gh 7/15/24 2023/2024 2  Drinking water should be essentially free of disease-causing microbes, but often , this is not the case. – A large proportion of the world’s population drinks microbially contaminated water, especially in developing countries. Using the best possible source of water for potable water supply and protecting it from microbial and chemical contamination is the goal. The burden of providing microbially safe drinking water supplies from contaminated natural waters rests upon water treatment processes – The efficiency of removal or inactivation of enteric microbes and other pathogenic microbes in specific water treatment processes – The ability of water treatment processes and systems to reduce waterborne diseases www.knust.edu.gh 7/15/24 2023/2024 3 Sustainable Development Goals (SDGs) www.knust.edu.gh 7/15/24 2023/2024 4 Render water safe, palatable, clear, colorless, odorless etc. Pre-Treatment Pass through a series of core screens to remove debris Cascade and settle it in the open ü settling particulate matter ü microbes exposed to lethal effect of sunlight ü reduce color by bleaching ü oxidizing the impurities that may affect taste. Sometimes pre-chlorination may be done when the bacterial count in the raw water is high with low turbidity BUT this may sometimes be a waste and expensive www.knust.edu.gh 7/15/24 2023/2024 5  www.knust.edu.gh 7/15/24 2023/2024 6  A schematic flow chart of a typical water treatment plant Raw water reservoir Storage Distribution system Disinfection Mixing chamber (Chlorination, UV, Ozone) Coagulation Filtration www.knust.edu.gh 7/15/24 2023/2024 7  The treatment process 1. Mixing Chamber Raw water mixed with a flocculant (a substance that promotes clumping) Examples of flocculants: Aluminum sulphate (ALUM) Aluminum hydroxide Ferrous sulphate NOW , Organic POLYMERS such as cellulose, lignin, and other starch derivatives Role: Encourages sedimentation, removes high numbers of microbes www.knust.edu.gh 7/15/24 2023/2024 8 Flocculation: Slow mixing (flocculation) provides some time to promote the aggregation and growth of the insoluble particles (flocs). The particles collide, stick together and grow larger. The resulting large floc particles are subsequently removed by gravity sedimentation (or direct filtration) Smaller floc particles are too small to settle and are removed by filtration. www.knust.edu.gh 7/15/24 2023/2024 9 2. Coagulation Removes suspended particulate and colloidal substances from water, including microorganisms. Coagulation: Colloidal destabilization Add alum (Aluminum Sulphate) or Ferric Chloride or Sulphate to the water by rapid mixing and controlled pH conditions. Insoluble aluminum or ferric hydroxide and aluminum or iron hydroxo complexes form These complexes entrap and adsorb suspended particulate and colloidal material. www.knust.edu.gh 7/15/24 2023/2024 10 3. Filtration This is through a series of clean sands of different sizes. Aim: Removes most microbes, particularly the protozoans (Giardia, Cryptosporidium) Rapid granular media Slow sand and other biological filters Membrane filters: micro-, ultra-, nano- and reverse osmosis Other physical-chemical removal processes Chemical coagulation, precipitation and complexation Adsorption: e.g., activated carbon, bone char, etc., Ion exchange: synthetic ion exchange resins, zeolites, etc. If the filter becomes blocked due to biofilms and retention of debris, it is cleaned by forcing clean water back through the filter (backwashing) **Cryptosporidium outbreak in Milwaukee and Oxford www.knust.edu.gh 7/15/24 2023/2024 11 4. Disinfection Physical: Reverse osmosis, heat, membrane filters Chemical: Chlorine, ozone, chlorine dioxide, iodine, other antimicrobial chemicals UV radiation www.knust.edu.gh 7/15/24 2023/2024 12 Physical methods: Reverse Osmosis (RO) Separation of particles contained in water from the aqueous component. It is primarily used for the desalination of seawater Advantage: It is relatively low in energy consumption Disadvantages: Potential clogging of RO membranes Chemical reaction with RO membranes (e.g. cellulose acetate membranes) if feed water is too acidic or alkaline www.knust.edu.gh 7/15/24 2023/2024 13  www.knust.edu.gh 7/15/24 2023/2024 14 Physical method: Distillation Uses heat to separate the aqueous phase of water from the solid phase or particulates It provides the purest water which is often free from all pathogens Disadvantage Not a practical alternative as a means for the production of potable water. Requires high energy input www.knust.edu.gh 7/15/24 2023/2024 15 Chemical method Chlorine may be added as the gas(Cl2), as Sodium Hypochlorine (NaOCl) Chlorine gas introduced into water hydrolyzes according to the following equation: Cl2+H20 ↔ HOCl + H+ + Cl- Chlorine gas Hypochlorous acid Hypochlorous acid dissociates in water according to the following: HOCl ↔ H+ + OCl- Hypochlorous acid Hypochlorite ion www.knust.edu.gh 7/15/24 2023/2024 16 Chlorination Chlorine can be added by gas, liquid or solid Chlorine hydrolyses to form hypochlorous acid which dissociates to produce hypochlorite Chlorine ensures microbiological safety in water supplies Residual chlorine is usually 0.1 to 0.3 mg/l high enough to kill most bacteria within 30mins but not high for protozoans and enteric viruses High chlorine affects taste www.knust.edu.gh 7/15/24 2023/2024 17  Mechanism of action of Chlorine Chlorine causes two types of damage to bacterial cells: Disruption of cell permeability: Free chlorine disrupts the integrity of the bacterial cell membrane, thus leading to loss of cell permeability and to the disruption of other cell functions. Exposure to chlorine leads to a leakage of proteins, RNA and DNA Damage to nucleic acids and enzymes. Chlorine also damages the bacterial nucleic acids as well as enzymes like catalase. www.knust.edu.gh 7/15/24 2023/2024 18 UV radiation: Thymine dimerization OZONE Protozoan cysts Bacteria spores Viruses Vegetative bacteria www.knust.edu.gh 7/15/24 2023/2024 19 Advantages of UV Efficient deactivation of bacteria and viruses No production of any known undesirable carcinogen No taste or odour problems No handling and storage of chemicals Small space required Disadvantages No disinfection residual in treated water Difficulty in determining UV dose Biofilm formation on the lamp Problems of cleaning and maintenance High cost of disinfection than chlorine Potential problems of photo-reactivation www.knust.edu.gh 7/15/24 2023/2024 20  Factors influencing disinfection Type of disinfectant Some disinfectants are stronger oxidants than others Type and age of microorganisms Spore forming bacteria are more resistant than vegetative bacteria Young microbes are easily destroyed than older ones Disinfectant concentration and contact time Inactivation of pathogens with disinfectants increases with time and ideally should follow a first order kinetics www.knust.edu.gh 7/15/24 2023/2024 21 Effect of pH-depends on the chemical in use E.g. pH controls the amount of Hypochlorous acid and hypochlorite ion in solution (Best pH range 5.5 and 7.5) Disinfection effectiveness increases with pH Temperature Pathogen and parasite inactivation increases as temperature increases Increase in temperature can also decrease disinfection because the disinfectant falls apart or is volatized Protective effect of Macro invertebrates www.knust.edu.gh 7/15/24 2023/2024 22  Other Considerations To maintain water quality during distribution: Construction materials should NOT promote growth. Non-metallic materials should comply with BS 6920, which includes a test for growth promotion. An equivalent standard does exist for metals which although they can become colonised with biofilms, cannot provide organic nutrients for growth www.knust.edu.gh 7/15/24 2023/2024 23  5. Storage Reservoirs, aquifers & other systems: store water protect it from contamination Factors influencing microbe reductions (site-specific) Detention time Temperature Microbial activity Water quality: particulates, dissolved solids, salinity Sunlight Sedimentation Land use Precipitation Runoff or infiltration www.knust.edu.gh 7/15/24 2023/2024 24  Ecological Sanitation (Eco-San) www.knust.edu.gh 7/15/24 2023/2024 25  What does sanitation include? Main Focus of Ecosan üsafe collection, storage, treatment and recycling M.Wafler of human excreta (faeces and urine) and sewage effluents üdrainage and disposal (re-use, recycling) of household grey water ümanagement/ recycling of (organic) solid wastes ütreatment and disposal/ recycling of drainage of stormwater ücollection and management of industrial waste E.Menger-Krug products ümanagement of hazardous wastes, including hospital wastes, and chemical/radioactive and other dangerous substances. www.knust.edu.gh Source: (3) 7/15/24 2023/2024 26 J.Heeb  Problems we currently face: Not working Sanitation… Users not involved in sanitation decisions Users do not acknowledge importance of sanitation Sanitation not adapted to local conditions No sense of ownership by the people No or insufficient maintenance à Sanitation systems are working improperly… or not at all www.knust.edu.gh 7/15/24 2023/2024 27  www.knust.edu.gh 7/15/24 2023/2024 28  Why EcoSan? www.knust.edu.gh 7/15/24 2023/2024 29  www.knust.edu.gh 7/15/24 2023/2024 30  www.knust.edu.gh 7/15/24 2023/2024 31  …are “flush and forget” sanitation solutions, where human wastes are flushed away with huge amounts of scarce freshwater, polluting rivers and the drinking water of people living further downstream. What happens at the end of the pipe? www.knust.edu.gh 7/15/24 2023/2024 32 What happens at the end of the pipe? If we are very lucky, there might be a “state of the art” conventional Sewage Treatment Plant: Which will need: Long sewer network & pumps to get the wastewater to the plant Electricity for aeration, pumps and other moving parts Skilled (and thus expensive) operation & maintenance staff Backup generator for powercuts Diesel for generator à Who will pay for this? www.knust.edu.gh 7/15/24 2023/2024 33  www.knust.edu.gh 7/15/24 2023/2024 34  www.knust.edu.gh 7/15/24 2023/2024 35  www.knust.edu.gh 7/15/24 2023/2024 36  www.knust.edu.gh 7/15/24 2023/2024 37  Alternative, sustainable solutions are needed! We need to rethink our sanitation approach; a new philosophy is needed! Sustainable sanitation solutions : 1. should be eco-friendly (no pollution of ground- and surface water) 2. need to be user-friendly 3. should need low maintenance 4. should be cost effective 5. should produce and not require energy (e.g. biogas) 6. are usually decentralized 7. should reuse nutrients, and water contained in wastewater www.knust.edu.gh 7/15/24 2023/2024 38 P. K.Jenssen Conradin J. Heeb J. Heeb K. Conradin K. Conradin P. Jenssen  The basic principle of ecological sanitation is to close the loop between sanitation and agriculture without compromising health www.knust.edu.gh 7/15/24 2023/2024 39  www.knust.edu.gh 7/15/24 2023/2024 40  www.knust.edu.gh 7/15/24 2023/2024 41  Double-vault Urine diverting composting Toilet www.knust.edu.gh 7/15/24 2023/2024 42  www.knust.edu.gh 7/15/24 2023/2024 43  www.knust.edu.gh 7/15/24 2023/2024 44  www.knust.edu.gh 7/15/24 2023/2024 45 Reuse Possibilities: Biogas as a sustainable energy source from wastewater: ð For cooking ð For heating ð For lights ð For electricity production Reuse of water after treatment: ð Irrigation in agriculture ð Industry, flush for toilets ð Recharge of groundwater www.knust.edu.gh 7/15/24 2023/2024 46  www.knust.edu.gh 7/15/24 2023/2024 47  www.knust.edu.gh 7/15/24 2023/2024 48  www.knust.edu.gh 7/15/24 2023/2024 49  www.knust.edu.gh 7/15/24 2023/2024 50  www.knust.edu.gh 7/15/24 2023/2024 51  Advantages of Ecosan Systems Improvement of health Promotion of recycling Conservation of resources Preference for modular, decentralised partial-flow systems Contribution to the preservation of soil fertility Improvement of agricultural productivity and hence contributes to food security Increasing user comfort/security, in particular for women and girls Source: (18) Promotion of a holistic, interdisciplinary approach. Cyclic Material-flow instead of disposal. www.knust.edu.gh 7/15/24 2023/2024 52  Sanitation conditions in Sub-Saharan Africa Figure 1.- Coverage with improved sanitation by region in 2004 (WHO and UNICEF, 2006) To achieve the year 2015 goal for urban and rural sanitation coverage in Sub-Saharan Africa – halving the percentage of those without access – 35 million people annually will have to be provided with service. www.knust.edu.gh 7/15/24 2023/2024 53  Cummulative Coverage Data for Sanitation in Regions 90 80 70 60 50 40 30 20 10 0 Western Central Gt. Accra Volta Eastern Ashanti B. Ahafo Northern Upper Upper East West www.knust.edu.gh 7/15/24 2023/2024 54  THE SANITATION LADDER Cost WC Pour flush Ecosan KVIP Not Acceptable Improved Pit Simple Pit Open defecation Fixed place defecation www.knust.edu.gh 7/15/24 2023/2024 55  MAJOR TECHNOLOGY OPTIONS of SANITATION SYSTEMS IN GHANA K(VIP) Aqua Privy Water Closets (WCs) Enviro - Loo Limited sewerage systems in Accra, Tema, Kumasi (some barracks and selected Housing Estates) Pan latrines ** Pit latrines ** Open defaecation *** Bio-Gas “Menu-Sack” Compost Toilet Etc. www.knust.edu.gh 7/15/24 2023/2024 56  www.knust.edu.gh 7/15/24 2023/2024 57  DON’T TOUCH ME !! www.knust.edu.gh 7/15/24 2023/2024 58  “Opportunities” - Practical Cases… WASTECARE Segment 1: Lack of space in “poor” areas Van’s Biological (Compost) Toilet is easily retrofited into existing building. (Accra Ghana) www.knust.edu.gh 7/15/24 2023/2024 59  Willingness-to-Pay versus Affordability ? Cost is important and affects choice! We need to be innovative and use more appropriate lower-cost designs & options if we $50 are $35 0 eac to meet SDGs h www.knust.edu.gh 7/15/24 2023/2024 60  VIP latrines control odour and fly nuisance In VIPs the superstructure is slightly offset from the pit, so that a vertical vent pipe can be installed Vent pipe is key to controlling both flies and odours Excreta are deposited into the pit via the squat-hole, the liquid (mainly urine) infiltrates into the surrounding soil, and the solids are digested anaerobically. www.knust.edu.gh 7/15/24 2023/2024 61  In Odour control wind blowing across the top of the vent pipe sucks out some of the air at the top of the Vent pipe and this is replaced by air from below; so this sets up an airflow pattern in which fresh air enters the pit through the squat-hole. Gases generated in the pit are then sucked up and out of the vent pipe, so leaving the superstructure totally odour-free www.knust.edu.gh 7/15/24 2023/2024 62  In fly control, gravid female flies know that human faeces are a good place to lay their eggs, so they are attracted to latrines by faecal odour. With VIP latrines all the odour comes out of the vent pipe, so this is where the gravid flies fly to. To prevent the flies entering the pit, a fly screen is placed over the top of the vent pipe. However, a few flies will enter the pit via the squat-hole and lay their eggs. www.knust.edu.gh 7/15/24 2023/2024 63  It is not uncommon to see cobwebs at the top of the vent pipe as spiders soon learn that this is a good place to catch their food. www.knust.edu.gh 7/15/24 2023/2024 64  www.knust.edu.gh 7/15/24 2023/2024 65  www.knust.edu.gh 7/15/24 2023/2024 66  Pathogen types potentially present in human excreta Type of Example organisms Examples of diseases caused pathogen by type of pathogen Bacteria Total coliforms Gastroenteritis Faecal coliforms Typhoid fever E. coli Salmonellosis Salmonella Cholera Faecal streptococci Enterococci Protozoa Giardia lamblia Giardiasis Cryoptosporidium Helminths Nematoda Roundworm infestation (worms) Ascaris lumbricoides Dwarf tapeworm Viruses MS2 coliphage Gastroenteritis Hepatitis A virus Respiratory disease Enteroviruses Meningitis, hepatitis Source: Metcalf & Eddy (2003), page 110 www.knust.edu.gh 7/15/24 2023/2024 67  Safe disposal of human excreta is second to the provision of pathogen free drinking water that promotes good health for every population Human faeces contain large numbers of microbes. For example one person with cholera excretes 1013 per day and since infective dose of cholera is 106 one person could infect 10 million people It is therefore important to separate disposal of excreta from drinking water To achieve this we must build latrines or septic tanks that confines excreta www.knust.edu.gh 7/15/24 2023/2024 68