Water Pollution Notes PDF

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

Department of Energy & Environment Water Pollution THAPAR INSTITUTE Department of Energy & UEN008: Energy and 1 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Water Cycle THAPAR INSTITUTE Department of Energy & UEN008: Energy and 2 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Water Pollution THAPAR INSTITUTE Department of Energy & UEN008: Energy and 3 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Water Pollution “The loss of any of the actual or potential bene cial 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 Department of Energy & UEN008: Energy and 4 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Characteristics of Water Characteristics- Physical – Solids, temperature, colour, odour, turbidity, oil and grease, conductivity, Chemical – Organics: proteins, carbohydrates, lipids, surfactants, phenols pesticides, emerging org., Inorganics: pH, chlorides, alkalinity, nitrogen, phosphorus, heavy metals Gases: Oxygen, hydrogen sul de, methane Aggregate organics – BOD, COD, TOC Biological – pathogens, indicators, viruses, invertebrates THAPAR INSTITUTE Department of Energy & UEN008: Energy and 5 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Sources of water pollution ❖ Point – single large sources ❖ Non-point - a di use source of pollution that cannot be a ributed to a clearly identi able, speci c physical location or a de ned discharge channel. general runo of sediments pesticide spraying fertilisers from farms THAPAR INSTITUTE Department of Energy & UEN008: Energy and 6 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment Point and non point sources of water pollution THAPAR INSTITUTE Department of Energy & UEN008: Energy and 7 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment Major Water Pollutants and Their Sources THAPAR INSTITUTE Department of Energy & UEN008: Energy and 8 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment Contaminants affecting water bodies Biodegradable organic ma er 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 Department of Energy & UEN008: Energy and 9 OF ENGINEERING & TECHNOLOGY 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, arti cial hormones – from domestic and animal wastes ❖ Stock pollutants : Pollutants that the environment has li le 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 Department of Energy & UEN008: Energy and 10 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment Nature and Characteristics of Wastewater THAPAR INSTITUTE Department of Energy & UEN008: Energy and 11 OF ENGINEERING & TECHNOLOGY 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 di usion 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 Department of Energy & UEN008: Energy and 12 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Water Quality Dissolved Oxygen Good 8–9 Slightly 6.7–8 pollute d Moderatel 4.5–6.7 y polluted Heavily 4–4.5 polluted Gravely Below 4 polluted THAPAR INSTITUTE Department of Energy & UEN008: Energy and 13 OF ENGINEERING & TECHNOLOGY 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 & ow weighted composite THAPAR INSTITUTE Department of Energy & UEN008: Energy and 14 OF ENGINEERING & TECHNOLOGY 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 Department of Energy & UEN008: Energy and 15 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Conti… Chemical Oxygen Demand (COD) Measures pollution potential of organic ma er organic ma er + oxidant ⇒ CO2 + H2O Does not di erentiate between biologically degradable & non-biodegradable organic ma er so COD value of samples are always higher than BOD's. Chemical oxygen demand (COD) is de ned as the amount of a speci ed 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 Department of Energy & UEN008: Energy and 16 OF ENGINEERING & TECHNOLOGY 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 Department of Energy & UEN008: Energy and 17 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Numerical on COD Problem A sewage water sample of 35 ml volume was re uxed 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  Biochemical Oxygen Demand (BOD) BOD is the traditional, most widely used test to establish concentration of organic ma er in wastewater samples (i.e., relative strength). BOD is based on the principle that if su cient oxygen is available, aerobic biological decomposition (i.e., stabilization of organic waste) by microorganisms will continue until all organic ma er 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 ve-day period in which the sample is held in dark, incubated conditions (i.e., 20°C or 68°F). THAPAR INSTITUTE Department of Energy & UEN008: Energy and 19 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Aggregate organics Biochemical Oxygen Demand (BOD) BOD is not a measure of any speci c pollutant A measure of amount of oxygen required by microorganisms engaged in stabilizing decomposable organic ma er 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 rst 5 days THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & Environment (DEE) UEN008: Energy and Environment 20  Aggregate organics Biochemical Oxygen Demand (BOD) Exponential decay curve THAPAR INSTITUTE Department of Energy & UEN008: Energy and 21 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Biochemical Oxygen Demand (BOD) Brie y, 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 bo le kept at 20⁰ C for 5 days. After 5 days again titrate the sample. The strength of waste water is determined by taking di erence BOD between = (DO –the DO initial ) *D DO and nal DO and then multiply by dilution Where t factor. i f BODt = biochemical oxygen demand at t days, [mg/L] DOi = initial dissolved oxygen in the sample bo le, [mg/L] DOf = nal dissolved oxygen in the sample bo le, [mg/L] D = Dilution Factor D = Vb/Vs Vb = sample bo le volume, usually 300 mL Vs = sample volume, [mL] THAPAR INSTITUTE Department of Energy & UEN008: Energy and 22 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Dilution Factor THAPAR INSTITUTE Department of Energy & UEN008: Energy and 23 OF ENGINEERING & TECHNOLOGY 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 Department of Energy & UEN008: Energy and 24 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Numerical on BOD Proble m Solution  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 e ciency of organic treatment by biological methods (value less than 0.3 would indicate non biodegradable waste) THAPAR INSTITUTE Department of Energy & UEN008: Energy and 27 OF ENGINEERING & TECHNOLOGY 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 Department of Energy & UEN008: Energy and 28 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Physical Parameters Solids Residue remaining after wastewater sample has been Total Solids evaporated (TS) and dried at a speci c temperature (103 – 105 deg. C) Total Volatile Burn o 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 lter of 2micro-m and suspended measured after drying the lter paper at 105 deg.C solids (TSS) Total Solids that passed through 2micro-m which dissolved comprises of colloidal and dissolved solids solids (TDS) THAPAR INSTITUTE Department of Energy & UEN008: Energy and 29 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Physical Parameters Solids Volatile suspended Burn o solids when TSS is ignited to 500 deg. solids (VSS) C Fixed suspended Residue after TSS ignition solids (FSS) Total volatile Solids that burn o when TDS is ignited to 500 dissolved solids deg.C (TVDS) Fixed dissolved The residue of the TVDS solids (FDS) Se le able solids Suspended solids that se le over time THAPAR INSTITUTE Department of Energy & UEN008: Energy and 30 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Physical Parameters Turbidity Measure of light transmi ing properties of water Measurement is based on comparison of intensity of light sca ered by sample vs that of standard (formazin solution) Analytical Techniques – Nephelometry Units – Nephelometric Turbidity Units (NTU) THAPAR INSTITUTE Department of Energy & UEN008: Energy and 31 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Conti… Colour Measured by Spectrophotometer Units – Platinum Cobalt Units (PCU) Temperature An important parameter as it a ects 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 UEN008: Energy and OF ENGINEERING & TECHNOLOGY Department of Energy & 32 Environment (DEE) Environment  Physico-chemical characteristics Aggregate organics Physical Chemical - Alkalinity - Nitrogen - Phosphorous - Sulphur - Metallic constituents THAPAR INSTITUTE Department of Energy & UEN008: Energy and 33 OF ENGINEERING & TECHNOLOGY 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 Department of Energy & UEN008: Energy and 34 OF ENGINEERING & TECHNOLOGY 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 sul de 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 Department of Energy & UEN008: Energy and 35 OF ENGINEERING & TECHNOLOGY 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 Department of Energy & UEN008: Energy and 36 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment Typical Unit Operations of a Wastewater treatment plant THAPAR INSTITUTE Department of Energy & UEN008: Energy and 37 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment Primary and Secondary Sewage Treatment (using Suspended Growth process) THAPAR INSTITUTE Department of Energy & UEN008: Energy and 38 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Screen First unit operation Objective -Removal of coarse and ne 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 39 Environment (DEE) Environment  Primary clari cation/sedimentation Separate the suspended solids, which can se le by gravity It used to remove Organic, residual inorganic solids and Chemical ocs produced during chemical coagulation and occulation The velocity of the ow 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 Department of Energy & UEN008: Energy and 40 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Sludge removal – circular clari er Scraper THAPAR INSTITUTE Department of Energy & UEN008: Energy and 41 OF ENGINEERING & TECHNOLOGY 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 in uence 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 Department of Energy & UEN008: Energy and 42 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Activated sludge processes (ASPs) ASP is an aerobic, continuous ow, treatment system that uses sludge with active populations of microorganisms to breakdown organic ma er in wastewater Activated sludge is a occulated mass of microbes The organic load (generally coming from primary treatment operations such as se ling, screening or otation) enters the reactor where the active microbial population (activated sludge) is present. The reactor is continuously aerated. The mixture then passes to a secondary se ling tank where the cells are se led. The cells are recycled in order to maintain su cient biomass to degrade the organic load as quickly as possible THAPAR INSTITUTE Department of Energy & UEN008: Energy and 43 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Activated Sludge Process THAPAR INSTITUTE Department of Energy & UEN008: Energy and 44 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Trickling lters A trickling lter (TF) is a aerobic a ached growth type wastewater treatment system that biodegrades organic ma er and can also be used to achieve nitri cation. 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 a ach themselves to the bed (also known as the lter media), which is covered with bacteria. The bacteria break down the organic waste and remove pollutants from the wastewater. THAPAR INSTITUTE Department of Energy & UEN008: Energy and 45 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Trickling Filter THAPAR INSTITUTE Department of Energy & UEN008: Energy and 46 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Trickling filters THAPAR INSTITUTE Department of Energy & UEN008: Energy and 47 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Anaerobic uidized bed process A combination of suspended growth and a ached 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 Department of Energy & UEN008: Energy and 48 OF ENGINEERING & TECHNOLOGY 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 Department of Energy & UEN008: Energy and 49 OF ENGINEERING & TECHNOLOGY Environment (DEE) Environment  Disinfection methods Chemical Physical Mechanical Radiation Halogens (Cl) Heating Chemical Gamma rad.& Ozone Solar insolation precipitators Cobalt-60 rad. Phenolics and bio lters Alcohols Metals Detergents, etc. THAPAR INSTITUTE Department of Energy & UEN008: Energy and 50 OF ENGINEERING & TECHNOLOGY 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 in uence action Contact time Concentration (chemical) Intensity/nature (physical) Temperature Organisms Nature of w/w THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY Department of Energy & Environment (DEE) UEN008: Energy and Environment 51 Thank Thank you You