Cork Institute of Technology. Summer 2006 CE4.4 Waste Treatment and Disposal Technology (Time: 3 Hours)

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1 Cork Istitute of Techology Bachelor of Egieerig (Hoours) i Chemical ad Process Egieerig - Award (NFQ Level 8) Summer 006 CE4.4 Waste Treatmet ad Disposal Techology (Time: 3 Hours) Aswer 4 questios. Aswer at least oe questio from each sectio. Use a separate aswer book for each questio. All questios carry equal marks. Examiers: Mr. I. O Sulliva Mr. P. Keedy Ms. O. O Coor Mr. K. Alle Mr. D. O Coor Prof. L. Kershebaum Sectio A Q1 a) What are the objectives of the Water Framework Directive? (5 marks) b) How is it beig implemeted i Irelad? (5 marks) c) Determie the amout of liquid alum (alum stregth by mass) required to precipitate phosphorus i a wastewater that cotais 8mgP/L. Also, determie the required alum storage capacity if a 30-day supply is to be stored at the treatmet facility. Based o laboratory testig, 1.5 mole of Al will be required per mole of P. The flowrate is 1,000m³/d. The followig data are for the liquid alum supply: Formula for liquid alum; Al (SO 4 ) 3.18H O Alum stregth 48% Desity of liquid alum solutio 1.kg/L (15 marks) Q a) The followig data is obtaied durig BOD testig of a wastewater stream i a treatmet plat. Time (days) BOD (mg/l) Calculate, usig the Fujimoto Method, the UBOD ad k values for the wastewater sample. (7 marks)

2 b) Explai briefly the theory behid the Fujimoto Method. (3 marks) c) List 3 limitatios of the BOD test (6 marks) d) BOD loadig to a waste-water treatmet plat may be equalized by usig a equalizatio basi. List the beefits ad drawbacks of flow equalizatio i treatmet plats. (9 marks) Sectio B Q3 (a) Usig the data give below for a complete mix activated sludge tak, determie (i) (ii) (iii) The system SRT How much oxyge is required i kg/d if the effluet soluble COD 5 mg/l The oxyge uptake rate (mg/lh) Aeratio tak MLVSS 3000 mg/l Aeratio tak volume 1000 m 3 Ifluet flowrate 5000 m 3 /d Waste sludge flowrate 59 m 3 /d Waste sludge VSS cocetratio 8000 mg/l Ifluet soluble COD cocetratio 400 mg/l (b) A complete mix activated sludge process is used to treat a dairy wastewater at a flowrate of 1000 m 3 /d with a degradable ifluet COD of 3000 mg/l ad BOD of 1875 mg/l. The MLSS cocetratio is 800 mg/l, MLVSS/MLSS ratio is 0.80, effluet TSS cocetratio is 0 mg/l, τ is 4 hours, recycle MLSS cocetratio is mg/l ad waste sludge flowrate from the recycle lie is 85.5 m 3 /d. Usig the give iformatio determie (i) the system SRT (ii) the F/M ratio (gbod/gmlvss.d) (iii) volumetric BOD loadig (kg/m 3 d) (iv) the observed yield (gtss/bod ad gtss/gcod) (v) the sythesis yield assumig that k d 0.1 gvss/gvssd ad f d 0.15 gvss/gvss

3 Q4 (a) Give the followig itrified effluet flow ad characteristics, desig a post aoxic suspeded growth system to achieve a effluet NO 3 -N cocetratio of.0 g/m 3. Determie (i) The required methaol dose (ii) The aoxic volume ad detetio time (iii) The waste sludge productio Flow 4000 m 3 /d NO 3 -N 60 mg/l Temperature 15 C TSS 0 mg/l (b) The followig desig iformatio is give for a domestic wastewater Flow m 3 /d BOD 60 mg/l Miimum temp 15 C TSS 40 mg/l Overflowrate m 3 /m d Miimum wettig rate 0.5 l/m s Usig the above iformatio, ad assumig 30 % BOD removal i primary clarificatio, a packig depth of 6.1 m, ad a value of of 0.5, determie the followig desig parameters for a tricklig filter treatmet system (i) Primary ad secodary clarifier diameters (m) (ii) Tricklig filter tower diameter (m) (iii) Packig volume (m 3 ) (iv) Recirculatio ratio if required 3

4 Sectio C Q5 (a) A aaerobic digester with a capacity of kg/d of sludge is to be treated by circulatio of sludge through a exteral hot water heat exchager. Assumig that the followig coditios apply, fid the heat required to maitai the required digester temperature. If all the heat were cut off for 4 h, what would be the average drop i temperature of the tak cotets, assumig that the feed ad drawoff is maitaied? Cocrete digester dimesios: Diameter 18 m Side depth 6 m Middepth 9 m Heat trasfer coefficiets: Dry earth embaked for etire depth U 0.68 W/m C Floor of digester i groud water U 0.85 W/m C Roof exposed to air U 0.91 W/m C Temperatures Air -5 C Earth ext to wall 0 C Earth below floor 5 C Icomig sludge 10 C Sludge cotets i digester 3 C Specific heat of sludge 400 J/kgK Desity of sludge 1000 kg/m 3 4

5 (b) The ultimate elemetal aalysis of a dried sludge yields the followig data Elemet Percet Carbo 5.1 Oxyge 38.3 Hydroge.7 Nitroge 6.9 Total 100 How may kg of air will be required per kg of sludge for its complete oxidatio? (c) Compute the fuel value of the sludge from a primary settlig tak havig a compositio by weight of 64.5 % C, 8,5 % Hydroge, 1 % Oxyge ad 4% Sulpher if (a) o chemicals are added ad (b) if the coagulatig solids amout to 10% by weight of the dry sludge. The amout of volatile solids preset is 75% Q6 Your local ewspaper is plaig a supplemet o the eviromet ad has approached you for a cotributio. The editor kows most of the relevat buzz words but does t seem to have a grasp of what they mea. Oe of his favourites is absorbtio equipmet. Write a short article, startig with a defiitio of absorbtio ad goig o to describe the various idustrial equipmet that is used. 5

6 Useful Equatios AR T 760 A T AR A PO 1 1 Dair 353 T C T H S A / Q S A / Q s S k D 1 S 1 k1 D S TA 0 AR T> 0 AR T N p 10.33(D)e 5 ( )( L / A) R 0kg/kg 0.80e 9LB 0.17LB O + 1.e PF k k (1.035) T 0 T 0 v P NP g AR 3 ( R OQSO)( 3.58m / kgo) 0 3 ( 10 g / kg)( 1440mi/ d) S S e o e kd q T T1 Tm l T / T 1 6

7 QY(S S) 1 (f )(k )YQ(S S)SRT 1 P + + QX + Q(TSS VSS ) o d d o X,TSS o,i o o 1 + (k d)srt (k d)srt 0.85 K[1 + (k)srt] S d S [SRT(Yk k d )] 1 ( o ) YS SSRT X 1+ kd SRT τ R Q S S 1.4P o o X,bio r Yr k X g su d C O a b H c N d + ( a + 0.5b 0.5b) O aco + 0.5cH O + 0.5dN Y Y 1+ k SRT d Q 3389C H P XV SRT ( O ) + 940S 8 bcod NO N Y 7