IEK 211 EQUIPMENT DESIGN FOR WATER TREATMENT [REKABENTUK PERALATAN PENGOLAHAN AIR]

Transcription

1 UNIVERSITI SAINS MALAYSIA Second Semester Examination 9/1 Academic Session April/May 1 IEK 11 EQUIMENT ESIGN FOR WATER TREATMENT [REKABENTUK ERALATAN ENGOLAHAN AIR] uration: hours Masa: [ jam] lease check that this examination paper consists of SEVEN pages of printed material before you begin the examination. [Sila pastikan bahawa kertas peperiksaan ini mengandungi TUJUH muka surat yang bercetak sebelum anda memulakan peperiksaan ini.] Instructions: Answer FIVE (5) questions. You may answer the questions either in Bahasa Malaysia or in English. [Arahan: Jawab LIMA (5) soalan. Anda dibenarkan menjawab soalan sama ada dalam Bahasa Malaysia atau Bahasa Inggeris.] In the event of any discrepancies, the English version shall be used. [Sekiranya terdapat sebarang percanggahan pada soalan peperiksaan, versi Bahasa Inggeris hendaklah diguna pakai.] /-

2 - - [IEK 11] 1. alculate the necessary amounts of lime and soda ash to soften a water which contains a total hardness of 15 mg/l as ao, alkalinity of 185 mg/l as ao, Mg mg/l as Mg +, Na + 8 mg/l as Na +, SO mg/l as SO 4 -, l - 1. mg/l as l -, NO - 1. mg/l as N, O 5.8 mg/l as O, and has a ph of A rapid-mix unit is to be designed for 5,-m /day raw water. Using a detention time of s, determine the size of the tank V and the motor horsepower of the mixer R i, assuming a shaft h and a motor efficiency M of 75% and 9%, respectively. Assume a water temperature of. Given: G = f μ µ = 1(1-4 ) kg/ms R i = R f / h M G = 8 s -1 One hp = Watts. The prototype detention time and overflow rate of a settling basin were calculated to be 44 min and.1m/min respectively. esign a rectangular settling basin using these values for a flow rate of m /d. Given: Z =υ t Z WZL υ = Q u h = horizontal velocity =.8m/h /-

3 - - [IEK 11] 4. A raw water to be treated by the lime-soda process to the minimum hardness possible has the following characteristics: O =.mg/l, a + =8mg/L, Mg + =1.mg/L, Na + = 46.mg/l, HO - = 15.5 mg/l and SO 4 - =16.mg/L. (a) heck if the numbers of equivalents of positive and negative ions are balanced. (5 marks) (b) For a flow of 5, m /day, calculate the chemical requirements and the mass solids and the volume of sludge produced. Assume that the lime used is 9% pure and the soda ash used is 85% pure. Also, assume that the specific gravity of the sludge is 1.4. = 1, O = 16, a = 4, M g= 4, Na =, H = 1., S =. For O : O + ao + HO ao + H O For Mg(HO ) : Mg(HO ) + ao + H O Mg(OH) + ao + H O For a(ho ) : a(ho ) + ao + HO ao + H O For aso 4 : aso 4 + Na O ao + Na SO 4 (5 marks) 5. A water treatment plant is being designed to process 5, m /d of water. Jar testing and pilot plant analysis indicate that an alum dosage of 4 mg/l with flocculation at a Gt value of 4. x 1 4 produces optimal results at the expected water temperatures of 15. etermine: (a) (b) The monthly alum requirement. The flocculation basin dimensions if three cross-flow horizontal paddles are to be used. The flocculator should be a maximum of 1 m wide and 5 m deep in order to connect appropriately with the settling basin. 4/-

4 - 4 - [IEK 11] (c) The power requirement. = υ A ρ A = dimensionless coefficient of = area of paddle blades, m ρ = density of water, kg/m drag, 1.8 for flat blades = G = A ρυ A ρυ Vμ 1/ 5/-

5 - 5 - [IEK 11] 1. Kira jumlah kapur dan serbuk soda yang diperlukan untuk melembutkan air yang mengandungi jumlah kekerasan 15 mg/l ao, kealkalian 185 mg/l ao, Mg mg/l sebagai Mg +, Na + 8 mg/l sebagai Na +, SO mg/l sebagai SO 4 -, l - 1. mg/l sebagai l -, NO - 1. mg/l sebagai N, O 5.8 mg/l sebagai O, dan mempunyai ph of Satu unit rapid-mix perlu direka untuk air mentah sebanyak 5,-m /hari. engan menggunakan masa retensi selama s, tentukan saiz tangki V dan kuasa motor pengkacau R i tersebut. Anggap keefisienan aci-enjin h dan motor M adalah 75% dan 9% masing masing serta suhu air adalah. iberi: G = f μ µ = 1(1-4 ) kg/ms R i = R f / h M G = 8 s -1 One hp = Watts. Masa pemendapan (retensi) bagi satu tangki prototaip dan kadar limpah ialah 44 min dan.1m/min masing-masing. Rancangkan suatu tangki pengendap segiempat tepat dengan menggunakan nilai-nilai yang diberi untuk kadar aliran sebanyak m /hari. iberi: Z =υ t Z WZL υ = Q u h = halaju mendatar =.8m/h 6/-

6 - 6 - [IEK 11] 4. Air mentah yang perlu dirawat melalui proses lime-soda untuk mengurangkan kekerasannya mempunyai sifat-sifat berikut: O =.mg/l, a + =8mg/L, Mg + =1.mg/L, Na + = 46.mg/l, HO - = 15.5 mg/l and SO 4 - =16.mg/L. (a) Tentukan sama ada nombor imbangan ion positif dan negative adalah seimbang. (5 markah) (b) Bagi kadar 5, m /hari, kirakan keperluan kimia dan berat pepejal serta isipadu endapan (sludge) yang dihasilkan. Anggap bahawa kapur yang digunakan adalah 9% tulen dan soda ash yang digunakan adalah 85% tulen. Anggap graviti spesifik endapan (sludge) adalah 1.4 = 1, O = 16, a = 4, Mg = 4, Na =, H = 1., S =. For O : O + ao + HO ao + H O For Mg(HO ) : Mg(HO ) + ao + H O Mg(OH) + ao + H O For a(ho ) : a(ho ) + ao + HO ao + H O For aso 4 : aso 4 + Na O ao + Na SO 4 (5 markah) 5. Satu loji rawatan air telah direkabentuk untuk memproses 5, m /d air. Jar test dan pilot plant analysis mendapati bahawa dos alum sebanyak 4 mg/l penggumpalan pada nilai Gt 4. x 1 4 menghasilkan keputusan optimum pada anggaran suhu air 15. Tentukan: (a) Keperluan alum dalam sebulan. (b) imensi tangki penggumpalan jika tiga palang padel aliran melintang digunakan. Alat penggumpal tersebut perlu bersaiz maksimum 1 m lebar dan 5 m dalam supaya sesuai disambungkan dengan tangki pemendakan. 7/-

7 - 7 - [IEK 11] (c) Kuasa yang diperlukan. = υ A ρ A = dimensionless coefficient of drag,1.8 for flat blades = area of ρ = density of paddle blades, m water, kg/m = G = A ρυ A ρυ Vμ 1/ - oooooo -