ESE2401: WATER SCIENCE AND TECHNOLOGY SEMESTER 2, AY2014/15 TUTORIAL SESSION 9 TUTORIAL 5 SHI XUEQING 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.carbonaceous biological matter oxidizing nitrogenous matter: mainly ammonium and nitrogen in biological matter.ammoniumnitrogen removing phosphates.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

SUMMARY 1.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

SUMMARY PROTON 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)