Characteristics of wastewater Prepared By Brian Patel Enrollment No. 130370106020

Introduction Two types of wastewater Domestic wastewater (Sewage) Industrial waste water Wide variation in quality of Industrial waste water Less variation in the characteristics of sewage

Composition of Sewage Contain organic & Inorganic matter, some gases & living organisms (mainly micro-organisms) Organic & Inorganic matter may be in suspended, colloidal & dissolved form. Organic matter include Carbohydrate like cellulose, starch, Sugar, cotton etc. Fats & Oil received from kitchen, garbage Nitrogeneous compound like protein & their decomposed product, including waste from urea, animal, fatty acid etc. Inorganic matter consist of salt & mineral like sand, gravel, dissolved salts, chlorides, sulphates etc.

Decomposition of Sewage Chemical process Biological Process Two type of Biological Process Aerobic Biological Process COHNS + Bacteria + O2  CO2 + H2O +Bacteria + Energy Anaerobic Biological Process In the absence of Oxygen & end product is Methane, H2S & ammonia.

Characteristics of Sewage Physical Characteristics Colour : Fresh sewage brown & yellowish colour With the passage of time it become septic -black colour Odour Fresh sewage not offensive odour Stale sewage – offensive odour ( All the oxygen disappeared from the sewage)

Temperature Higher temperature –biological Activity more means demand of oxygen more but solubility of DO at higher temp. decrease Turbidity Due to suspended solids Measured by Jackson turbiditymeter Nephelometric turbidity meter

Chemical Characteristics Solids : Sewage contain 99.9 % sewage & 0.1 % solid Solids may be organic or inorganic T.S. = S.S + D.S. 45% organic solids & 55 % inorganic solids pH : pH > 7 Alkalinity pH< 7 Acidic pH = 7 Neutral Fresh sewage is alkaline, with the passage of time acidic pH determination is important in biological treatment, Chemical coagulation, chlorination(Disinfection)

Nitrogen Compound One or more of the following form Free amonia – First stage of decomposition Organic Nitrogen – Total Organic nitrogen Nitrite – Partly decomposition of organic matter Nitrate – fully decomposition of organic matter Chloride content Main sources in sewage kitchen waste, human feces & urinary discharge Industry like ice-cream plant, meat salting etc.

Fat, Oil & grease Main sources – from garage, kitchen of hotel & restaurant, discharge of animal & vegetable matter Major problem in biological process – due to scum on the surface & affect oxygen diffusion Toxic Compound Copper, lead, silver, Chromium, Arsenic, Phenol, boron, Cyanide etc are toxic compound Major source – Industrial wastewater Affect biological treatment

Sulphide, sulphate & Hydrogen Sulphide Gases In Aerobic decomposition Sulphur  Sulphide  Sulphate In Anaerobic Decomposition Sulphur  Sulphide with H2S + CH4 Dissolved Oxygen Amount of oxygen dissolve in water For the survival of Dissolve oxygen minimum 4 mg/lit dissolve oxygen is essential It prevent the formation of obnoxious odour Factor affect D.O. Temperature TDS of water

BOD (Biochemical Oxygen Demand) Two type of organic matter Biodegradeable & Non biodegradable BOD means amount of oxygen required by bacteria for the decomposition of biodegradable organic matter under aerobic condition Widely used to determine the pollution strength of domestic & industrial waste Useful in the design of wastewater treatment plant First stage BOD- related to the carbonaceous organic matter Second stage BOD – Related to the nitrogeneous matter Measured for 5 days at 20 degree centigrate or 3 day 27 degree centigrate degrr

Equation for the first stage BOD Yt = L [1- (10)-kdt] (Kd)t = (Kd)20.[1.047]t-20 Limitation of BOD Measure only biodegradable organic matter Very long duration i.e. 5 days Pretreatment is needed if toxic COD (Chemical Oxygen Demand) Measure both biodegradable & Non biodegradable organic matter Takes 3 hrs Value is always higher than BOD

BOD/COD ratio If BOD/COD > 0.6 biological treatment is feasible. If BOD/COD between 0.3 to 0.6 acclimatization is essential If BOD/COD is < 0.3 Biological treatment is not possible Relative Stability S = 100(1-0.794) t20 S = 100(1-0.630) t37

Characteristics of Industrial wastewater Organic substance Inorganic substance Acid & alkalies Toxic Substances Color producing substance Oil

Treatment of Industrial waste water Equalization – to get uniform quality of wastewater Neutralization- Neutralize excess acidity or alkalinity Physical treatment Sedimentation- For the removal of settalable solid Biological Treatment If BOD/COD > 0.6 highly biodegradable If BOD/COD < 0.3 Biological treatment is not feasible If BOD/COD between 0.3 to 0.6 acclimatization is needed for the biological treatment Chemical Treatment Chemical coagulation Adsorption Chemical Oxidation

Disposal of Sewage Disposal of sewage by Natural method – Dilution, on Land Artificial Method Screening & detritus removal Sedimentation with or without chemical Biological Treatment Types of receiving water body Ocean or Sea – More dilution factor, high TDS Lakes – Stagnant water Perennial river- Flowing water Estuaries

Self Purification of Natural Stream Normal Biological cycle in stream

Natural force Dilution – Higher dilution ratio– Aerobic condition exit Sedimentation – Concentration of wastewater get reduced Sunlight – stimulate the growth of algue Oxidation – continue till complete oxidation of organic matter take place. Most important action responsible for effecting self purification

Factors Affecting Self Purification Temperature Velocity Rate of re-aeration Amount & type of organic matter Available initial DO Types of micro-organism present

Factors Affecting Self Purification Temperature - Higher temp. biological activity more but solubility of dissolved oxygen less Velocity – if high- Oxygen diffusion rapidly if low – oxygen diffusion slowly Rate of re-aeration – Greater the rate, rapid the self purification Amount & type of organic matter – more biodegradable organic matter , more oxygen demand- D.O. decrease

Available initial DO – Greater at the time of discharge earlier the self purification Types of micro-organism present – Algue present with bacteria – Oxygen added by algue

Zone of Pollution in River or Stream Zone of degardation Zone of Active Decomposition Zone of recovery Zone of clear water

Zone of Pollution

Oxygen Sag Curve

Oxygen Sag Curve Deoxygenation & Reoxygenation occur simultaneously If deoxygenation > Reoxygenation  Oxygen deficit incresing If deoxygenation = Reoxygenation Critical Point If deoxygenation < Reoxygenation  Oxygen deficit decreasing & ultimately goes to Zero

Sewage Sickness Clogging of soil pore Measure to prevent sewage sickness Primary treatment of sewage – Sedimentation Choice of land – Sandy soil Giving rest to the land Rotation of crop Applying shallow depth