ESE2401: WATER SCIENCE AND TECHNOLOGY

SEMESTER 2, AY2014/15

TUTORIAL SESSION 9TUTORIAL 5

SHI XUEQINGERISX@NUS.EDU.SG

DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING

NATIONAL UNIVERSITY OF SINGAPORE

Coagulation indicates the process through which colloidal particles and very fine solid suspensions are destabilized so that they can begin to agglomerate if the conditions are appropriate

Flocculation refers to the process by which destabilized particles actually conglomerate into larger aggregates so that they can be separated from the wastewater

Sedimentation

Filtration

In a sewage (or industrial wastewater) treatment plant, the activated sludge process is a biological process that can be used for one or several of the following purposes:

•oxidizing carbonaceous biological matter.

•oxidizing nitrogenous matter: mainly ammonium and nitrogen in biological matter.

•removing phosphates.

•generating a liquor that is low in dissolved or suspended material.

SUMMARY

• Unit conversion

• Material balance

• Residence time

• Molarity/normality

• Water quality parameters

1. Alkalinity

2. Hardness (TH, CH, NCH)

3. TS, TDS, TSS, VSS

4. Ionic strength• Henry’s Law

• Relative humidity

SUMMARY1. Equations

1. Mass conservation

2. Equilibrium

3. Electroneutrality (Charge balance)

4. Proton condition

2. Solid dissolution/precipitation

3. Acid base equilibrium

1. Strong acid/base

2. Weak acid/base

4. Open/closed carbonate system

5. Solving equilibrium problems

1. Analytical approach

2. pC-pH diagram

SUMMARYPROTON CONDITION （ PRL）

ELEMENTRAY REACTION KINETICS （ expression of rate, k, Ƭ）

REDOX STOICHIOMETRY (element oxidation state, element balance, charge balance)

BIOCHEMICAL OXYGEN DEMAND (BOD(t)=BODu-BODt, first order kinetics)

BATCH REACTOR KINETICS (sequential first-order reaction

A →B →C, d[B]/dt=R1-R2=k1 [A]-k2 [B])

THREE　CLASSIC MODELS (batch reactor, CMFR, PFR)