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Lecture One Lecture One

INTRODUCTION TO BASICS OF WASTEWATER, SANITATION AND DRAINAGE

Introduction Introduction

Water Use Cycle

WastewaterWastewater is simply that part of the water supply to the

community or to the industry which has been used for different purposes and has been mixed with solids either suspended or dissolved.

Wastewater is 99.9% water and 0.1% solids.

The main task in treating the wastewater is simply to remove most or all of this 0.1% of solids.

WastewaterWastewater People excrete 100-150 grams wet

weight of feces And 1-1.3 liters of urine per person

per day.

DIFINITIONSDIFINITIONS Sewer: Sewers are under ground pipes

or conduits which carry sewage to points of disposal.

Sewage: The Liquid waste from a community is called sewage. Sewage is classified into sewage. The non domestic sewage is classified into industrial, domestic-non and domestic commercial, institutional and any other sewage that is not domestic.

DIFINITIONS (DIFINITIONS (contdcontd…) …) Sewerage: The entire system used for

collection, treatment and disposal of Liquid waste. This includes pipes, manholes, and all structures used for the above mentioned purposes.

Infiltration: It is the water which inters the sewers from ground water through Leaks from loose joints or cracks.

Inflow: It is the water which inters the sewers from the manholes during rainfall events.

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Classification of wastewater Classification of wastewater Gray water: Washing water from the

kitchen, bathroom, laundry (without faeces and urine)

Black water: Water from flush toilet (faeces and urine with flush water)

Yellow water: Urine from separated toilets and urinals

Brown water: Black water without urine or yellow water

Quality of wastewater Quality of wastewater

The quality of wastewater determines the type and degree of treatment required.

Example: in case of biological treatment amount of organic matter in domestic wastewater determines the degree of biological treatment required.

Quality of wastewater Quality of wastewater

Many parameters have been used to measure the concentration of organic matter in wastewater.

The following are the most common used methods:

Biochemical Oxygen Demand (BOD) Chemical oxygen demand (COD) Total Organic Carbon (TOC)

Biochemical Oxygen Demand Biochemical Oxygen Demand (BOD)(BOD) BOD5 is the oxygen equivalent of organic

matter.

Example 1. Example 1.

10 mL of a wastewater sample are placed in a 300-mL BOD bottle. The initial DO of the sample is 8.5 mg/L. The DO is 3 mg/L after 5 days. What is the 5-day BOD?

Chemical oxygen demand Chemical oxygen demand (COD)(COD)

It is the amount of oxygen necessary to oxidize all the organic carbon completely to CO2 and H2O.

Is measured by oxidation with potassium dichromate (K2Cr2O7) in the presence of sulfuric acid and silver and expressed in milligram per liter.

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Total Organic Carbon (TOC)Total Organic Carbon (TOC)

This method measures the organic carbon existing in the wastewater by injecting a sample of the WW in special device in which the carbon is oxidized to carbon dioxide then carbon dioxide is measured and used to quantify the amount of organic matter in the WW. This method is only used for small concentration of organic matter.

Total Organic Carbon (TOC)Total Organic Carbon (TOC)

Theoretical oxygen (Theoretical oxygen (ThODThOD)) If the chemical formula of the organic matter

existing in the WW is known the ThOD may be computed as the amount of oxygen needed to oxidize the organic carbon to carbon dioxide and a other end products.

Example 2Example 2 Calculate the Theoretical Oxygen Demand

(ThOD) for sugar C12 H22 O11 dissolved in water to a concentration of 100 mg/L. Calculate "TOC".