Water Pollution - UEN008 PDF

Department of Energy & Environment Water Pollution THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 1 Environment (DEE) Environment ...

Department of Energy & Environment Water Pollution THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 1 Environment (DEE) Environment  Water Cycle THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 2 Environment (DEE) Environment  Water Pollution THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 3 Environment (DEE) Environment  Water Pollution “The loss of any of the actual or potential beneficial uses of water caused by any change in its composition due to human activity". Water pollution is the contamination of water bodies, usually as a result of human activities. Water bodies include lakes, rivers, aquifers, ground water. Water pollution results when contaminants are introduced into the natural environment in excess concentrations. THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 4 Environment (DEE) Environment  Sources of water pollution Point – single large sources Non-point - a diffuse source of pollution that cannot be attributed to a clearly identifiable, specific physical location or a defined discharge channel. general runoff of sediments pesticide spraying fertilisers from farms THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 5 Environment (DEE) Environment Point and non point sources of water pollution THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 6 Environment (DEE) Environment Major Water Pollutants and Their Sources THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 7 Environment (DEE) Environment Contaminants affecting water bodies  Biodegradable organic matter  Suspended, colloidal and dissolved solids  Nutrients  Pathogens  Acidic, basic and ionic species  Soaps and detergents  Pesticides  Colour and odour causing substances  Volatile organics  Recalcitrant and refractory organics  Thermal / Radioactive material THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 8 Environment (DEE) Environment  Categories  Fund pollutants : Fund pollutants are those for which the environment has some absorptive capacity Degradable – organic residuals that are broken down by bacteria Thermal – injection of heat into water source Eutrophic – excessive nutrients (nitrogen, phosphorous) leading to too much aquatic plant growth Persistent pollutants – inorganic/synthetic chemicals that are only partially broken down Bacteria, viruses, artificial hormones – from domestic and animal wastes  Stock pollutants : Pollutants that the environment has little or no absorptive capacity is called stock pollutants Minerals and inorganic/organic chemicals that cannot be removed by natural processes (lead, cadmium, mercury, some agrochemicals, persistent synthetic chemicals, non-biodegradable plastics, and heavy metals) THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 9 Environment (DEE) Environment Nature and Characteristics of Wastewater THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 10 Environment (DEE) Environment  Dissolved Oxygen (DO)  Important measure of water quality  Oxygen is marginally soluble in water & inversely proportional to temperature  Maximum DO at water temperature of 16 deg.C is 10 mg/L  DO analysis measures the amount of gaseous oxygen (O2) dissolved in an aqueous solution  Oxygen gets into water by diffusion from the surrounding air, by aeration (rapid movement), and as a product of photosynthesis.  As dissolved oxygen levels in water drop below 5 mg/l, aquatic life is put under stress. THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 11 Environment (DEE) Environment  Water Quality Dissolved Oxygen Good 8–9 Slightly 6.7–8 polluted Moderately 4.5–6.7 polluted Heavily 4–4.5 polluted Gravely Below 4 polluted THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 12 Environment (DEE) Environment  Physio-chemical characteristics Aggregate organics Total Organic Carbon (TOC) Chemical Oxygen Demand (COD) Biochemical Oxygen Demand (BOD) Chemical Organics – Proteins, carbohydrates, lipids, surfactants, phenols, pesticides, etc. Inorganics – pH, chlorides, alkalinity, nitrogen, phosphorous, heavy metals, Gases - hydrogen sulphide, methane, etc. Physical Solids, temperature, colour, odour, turbidity, oil and grease, conductivity Sampling – Grab, composite & flow weighted composite THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 13 Environment (DEE) Environment  Conti… ThOD This is the total amount of oxygen required to completely oxidize a known compound to CO2 and H2O. It is a theoretical calculation that depends on simple stoichiometric principles. It can only be calculated on compounds of known composition. C6H12O6 + 6O2 = 6CO2 + 6H2O Molecular weight of C6H12O6 = 180 = 192/180 = 1.067 g O2/g of C6H12O6 = 1067 mg/l THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 14 Environment (DEE) Environment  Conti… Chemical Oxygen Demand (COD) Measures pollution potential of organic matter organic matter + oxidant ⇒ CO2 + H2O Does not differentiate between biologically degradable & non-biodegradable organic matter so COD value of samples are always higher than BOD's. Chemical oxygen demand (COD) is defined as the amount of a specified oxidant that reacts with the sample under controlled conditions. Potassium dichromate (K2Cr2O7) is used as an oxygen source to oxidize the organic carbon present in the sample Expressed in equivalent amount of oxygen. THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 15 Environment (DEE) Environment  Aggregate organics Procedure The chemical oxygen demand (COD) of a waste is measured in terms of the amount of potassium dichromate (K2Cr2O7) reduced by the sample during 2 h at 150°C Sample is titrated with Ferrous Ammonium Sulphate(FAS) by using ferroin indicator. The following formula is used to calculate COD: COD(mg/l as O2) = where B is the volume of FAS used in the blank sample, S is the volume of FAS in the original sample, and M is the molarity of FAS 8000 = milli equivalent weight of oxygen (8) ×1000 mL/L. If milliliters are used consistently for volume measurements, the result of the COD calculation is given in mg/L. THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 16 Environment (DEE) Environment  Numerical on COD Problem A sewage water sample of 35 ml volume was refluxed with 10 ml of 0.25 N K2Cr2O7 solution. The remaining dichromate was titrated against 0.2 N ferrous ammonium sulfate (FAS) and volume of FAS consumed was 3.5 ml. Titration of the digested blank sample consumed 30 ml of FAS (0.2 N). Calculate the COD of the sewage. Solution: The formula of COD is COD = (Blank-Test)*M*8*1000 Volume of sample 30−3.5 ×0.2×8×1000 𝐶𝑂𝐷 = 35 COD = 1211.43 mg/l  Biochemical Oxygen Demand (BOD) BOD is the traditional, most widely used test to establish concentration of organic matter in wastewater samples (i.e., relative strength). BOD is based on the principle that if sufficient oxygen is available, aerobic biological decomposition (i.e., stabilization of organic waste) by microorganisms will continue until all organic matter is consumed. The BOD test is also known as "BOD5" since it is based on the accurate measure of DO (dissolved oxygen) at the beginning and end of a five-day period in which the sample is held in dark, incubated conditions (i.e., 20°C or 68°F). THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 18 Environment (DEE) Environment  Aggregate organics Biochemical Oxygen Demand (BOD) BOD is not a measure of any specific pollutant A measure of amount of oxygen required by microorganisms engaged in stabilizing decomposable organic matter Important factors of variations - Temperature; Time; Light BOD measurements – BOD5 & BOD3 BOD5 – BOD test carried out in an BOD incubator at 20 deg.C for 5 days Why 5 day BOD ? Oxidation of biochemical oxygen demanding substances is an exponential decay curve. Decay constant is usually that most of these substances are oxidized (85%) in the first 5 days THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 19 Environment (DEE) Environment  Aggregate organics Biochemical Oxygen Demand (BOD) Exponential decay curve THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 20 Environment (DEE) Environment  Biochemical Oxygen Demand (BOD) Briefly, the BOD test employs a bacterial seed to catalyze the oxidation of 300 mL of full-strength or diluted wastewater. The initial sample is titrated with N/40 Sodium Thiosulfate using starch as indicator. Another bottle kept at 20⁰ C for 5 days. After 5 days again titrate the sample. The strength of waste water is determined by taking difference between the initial DO and final DO and then multiply by dilution factor. BOD = (DO – DO ) *D t i f Where BODt = biochemical oxygen demand at t days, [mg/L] DOi = initial dissolved oxygen in the sample bottle, [mg/L] DOf = final dissolved oxygen in the sample bottle, [mg/L] D = Dilution Factor D = Vb/Vs Vb = sample bottle volume, usually 300 mL Vs = sample volume, [mL] THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 21 Environment (DEE) Environment  Dilution Factor THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 22 Environment (DEE) Environment  Method for the measuring of BOD BODt = UBOD (1-e-kt) BODt = BOD after t days (mg/l) UBOD = Ultimate BOD (mg/l) k = BOD rate constant at particular temperature (day-1) t = Time in days THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 23 Environment (DEE) Environment  Numerical on BOD Problem For a sample of sewage, 𝐵𝑂𝐷5 is 350 mg/l at 20°C which is 57% of the ultimate BOD. Calculate 𝐵𝑂𝐷4 of the sample at 30 °C. Consider the value of θ as 1.047. Solution Since BOD5 is 57% of UBOD UBOD = BOD5/0.57 = 350/0.57 = 614.03 mg/l Using equation 𝐵𝑂𝐷5 = 𝑈𝐵𝑂𝐷 1 − 𝑒 −𝑘𝑡 350 = 614.03 1 − 𝑒 −5𝑘 k = 0.17 per day at 20 oC Using van’t Hoff-Arrhenius model 𝑘 𝑇 = 𝑘20 𝜃 𝑇−20 𝑘30 = 0.17(1.047)30−20 k30 = 0.27 per day Using equation 𝐵𝑂𝐷4 = 𝑈𝐵𝑂𝐷 1 − 𝑒 −𝑘𝑡 𝐵𝑂𝐷4 = 614.03 1 − 𝑒 −0.27𝑥4 BOD4 = 405.51 mg/l  Aggregate organics BOD and COD relationship COD values are higher than BOD values in nearly all cases, because COD includes both degradable and non-biodegradable substances whereas BOD contains only bio-degrabable Greater BOD to COD ratio – higher the efficiency of organic treatment by biological methods (value less than 0.3 would indicate non biodegradable waste) THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 26 Environment (DEE) Environment  Aggregate organics Total Organic Carbon (TOC) It is used to express the pollution load in terms of carbon content It is measured directly by using the instrument called TOC analyzer Theoretical calculation can be done if the chemical formula of the given compound is known. THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 27 Environment (DEE) Environment  Physical Parameters Solids Residue remaining after wastewater sample has been Total Solids evaporated and dried at a specific temperature (103 – 105 (TS) deg. C) Total Volatile Burn off solids when TS is ignited to 500 deg.C solids (TVS) Total Fixed Left out solids after ignition of TS solids (TFS) Total Portion of TS retained in filter of 2micro-m and measured suspended after drying the filter paper at 105 deg.C solids (TSS) Total Solids that passed through 2micro-m which comprises of dissolved colloidal and dissolved solids solids (TDS) THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 28 Environment (DEE) Environment  Physical Parameters Solids Volatile suspended Burn off solids when TSS is ignited to 500 deg.C solids (VSS) Fixed suspended Residue after TSS ignition solids (FSS) Total volatile dissolved solids Solids that burn off when TDS is ignited to 500 deg.C (TVDS) Fixed dissolved solids The residue of the TVDS (FDS) Settle able solids Suspended solids that settle over time THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 29 Environment (DEE) Environment  Physical Parameters Turbidity Measure of light transmitting properties of water Measurement is based on comparison of intensity of light scattered by sample vs that of standard (formazin solution) Analytical Techniques – Nephelometry Units – Nephelometric Turbidity Units (NTU) THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 30 Environment (DEE) Environment  Conti… Colour Measured by Spectrophotometer Units – Platinum Cobalt Units (PCU) Temperature An important parameter as it affects the chemical and biochemical reactions and the rates of these reactions Electrical Conductivity A measure of the ability of solution to conduct electric current EC is surrogate measure of TDS [TDS mg/L = EC x 0.55 to 0.70] Units - MilliSiemens/ meter THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 31 Environment (DEE) Environment  Physico-chemical characteristics  Aggregate organics  Physical  Chemical - Alkalinity - Nitrogen - Phosphorous - Sulphur - Metallic constituents THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 32 Environment (DEE) Environment  Conti… Alkalinity Hydroxides, carbonates and bicarbonates Common – Ca & Mg bicarbonates Importance – Biological treatment Nitrogen Importance – Nutrient Forms – NH3, NH4+, NO2- and NO3- & Org. N Measurements – Amm. N., Inorg. N., Kjeldahl N., Org. N THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 33 Environment (DEE) Environment  Physico-chemical characteristics Phosphorous Aqueous forms – Orthophosphates, polyphosphate & organic phosphates Importance as nutrient Sulphur Aqueous form – sulphate Reduced to sulphide and further to hydrogen sulfide Formation of sulphuric acid and pipe corrosion Metallic constituents Priority pollutants – Cd, Cr, Cu, Fe, Pb, Mn, Hg, Ni & Zn Micronutrients / Toxicants Measurable forms – dissolved, suspended, acid extractable THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 34 Environment (DEE) Environment  Wastewater Treatment Primary – Removes Solids Physical Operations – Screening , Sedimentation Secondary – Removes Organics Biological and Chemical Operations Tertiary – Removes Nutrients Biological and Chemical Operations THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 35 Environment (DEE) Environment Typical Unit Operations of a Wastewater treatment plant THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 36 Environment (DEE) Environment Primary and Secondary Sewage Treatment (using Suspended Growth process) THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 37 Environment (DEE) Environment  Screen First unit operation Objective -Removal of coarse and fine objects, which may get entangled in mechanical equipment e.g., grit chambers, sedimentation tanks, etc. -Protection of pump impellers. -Used to remove Rocks, leaves, paper, plastic rags and other materials Coarse Screens: provide a bar screen with relatively large openings of 25 mm. Medium Screens: Clear openings of 12 mm. Fine Screens: Clear openings of 5 mm THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 38 Environment (DEE) Environment  Primary clarification/sedimentation Separate the suspended solids, which can settle by gravity It used to remove Organic, residual inorganic solids and Chemical flocs produced during chemical coagulation and flocculation The velocity of the flow can be reduced by increasing the length of travel and by detaining the particles for longer time in the sedimentation tank The size of the particles can be altered by adding some chemicals In plain sedimentation tank 60-65% of suspended solids and 30-35% of the BOD removal can be achieved THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 39 Environment (DEE) Environment  Sludge removal – circular clarifier Scraper THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 40 Environment (DEE) Environment  Fundamentals of biological treatment Most of the enzymatic reactions involve redox reactions i.e., addition/removal of oxygen/hydrogen The electron acceptor is based on surrounding medium and cellular characteristics -In anaerobic reactions – an oxidized compound is electron acceptor -In aerobic reactions – oxygen is acceptor Environmental factors influence microbial growth Temperature  Psychrophilic – (-10 to 30 deg.C) opt. 12–18 0C  Mesophilic – (20 to 50 deg.C) opt. 25-40 0C  Thermophilic – (35 to 75 deg.C) opt. 55-65 0C  Facultative THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 41 Environment (DEE) Environment  Activated sludge processes (ASPs) ASP is an aerobic, continuous flow, treatment system that uses sludge with active populations of microorganisms to breakdown organic matter in wastewater Activated sludge is a flocculated mass of microbes The organic load (generally coming from primary treatment operations such as settling, screening or flotation) enters the reactor where the active microbial population (activated sludge) is present. The reactor is continuously aerated. The mixture then passes to a secondary settling tank where the cells are settled. The cells are recycled in order to maintain sufficient biomass to degrade the organic load as quickly as possible THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 42 Environment (DEE) Environment  Activated Sludge Process THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 43 Environment (DEE) Environment  Trickling filters A trickling filter (TF) is a aerobic attached growth type wastewater treatment system that biodegrades organic matter and can also be used to achieve nitrification. The wastewater trickles through a circular bed of coarse stones or plastic material. A rotating distributor (a rotating pipe with several holes across it) evenly distributes the wastewater from above the bed. The microorganisms in the wastewater attach themselves to the bed (also known as the filter media), which is covered with bacteria. The bacteria break down the organic waste and remove pollutants from the wastewater. THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 44 Environment (DEE) Environment  Trickling Filter THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 45 Environment (DEE) Environment  Trickling filters THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 46 Environment (DEE) Environment  Anaerobic fluidized bed process A combination of suspended growth and attached growth process Anaerobic microbes grow on the surface of the medium, expanding the apparent volume of the medium; hence this reactor is also designated an "expanded bed reactor" THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 47 Environment (DEE) Environment  Disinfection Partial destruction of disease causing (pathogenic) organisms Characteristics of an ideal disinfectant Availability Deodorizing ability Homogeneity Extraneous material interaction Non-corrosive and non-staining Toxic to microbes Penetration Solubility and stability THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 48 Environment (DEE) Environment  Disinfection methods Chemical Physical Mechanical Radiation Halogens (Cl) Heating Chemical Gamma rad.& Ozone Solar insolation precipitators and Cobalt-60 rad. Phenolics biofilters Alcohols Metals Detergents, etc. THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 49 Environment (DEE) Environment  Disinfectant action Damage to cell wall and disturbance in cell permeability – phenolics and detergents Damage to protoplasm and cell molecules – Radiation Molecular alterations and Inhibition of enzyme activity – Chlorine and other halogens Factors that influence action Contact time Concentration (chemical) Intensity/nature (physical) Temperature Organisms Nature of w/w THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & UEN008: Energy and 50 Environment (DEE) Environment Thank You