1. The following information is provided for an activated sludge system design: Parameter Symbol Value Units Flow rate Q 10000 m³/d Influent BOD So 150 mg/L Effluent BOD S 2 mg/L Hydraulic residence time Ꮎ 4 hr Mean cell residence time Oc 6 d Maximum specific growth rate μm 3 1/d Half saturation constant Ks 40 mg/L Yield coefficient Y 0.5 Endogenous decay coefficient b 0.08 1/d Death rate coefficient γ 0.04 1/d Determine: a) The aeration tank biomass concentration (X) in mg/L b) The aeration tank oxygen requirement in kg/d c) The rate of biomass wasting in kg/d

An activated sludge system using CSTR with sludge recycle has an influent flow rate (Q°) of 2.5 MGD that contains BOD of 200 mg/L. The volume of the aeration tank (CSTR) is 0.6 million gallons. The MLVSS (assume this is X,) in the aeration tank is 2000 mg VSS/L and the decay rate (b) is 0.1/day. The effluent from the secondary clarifier meets NPDES standards for suspended solids and BOD. The concentration of the settled sludge exiting the bottom of the secondary clarifier is 15,000 mg VSS/L. The sludge waste flow rate (Q") is 1 % of the influent flow rate, and the effluent flow rate (Qª) is ~99% of the influent flow rate. а) What is the hydraulic retention time, 0 (d)? b) What is the solids retention time, 0x (d)? Activated sludge with recycle с) What is the F/Ma ratio?

1a. In water and wastewater containing particles that tend to coalesce upon colliding with other particles, and having a range of particle sizes, fast settling larger particles overtake slow settling smaller particles (in accordance with Stokes' law) possibly colliding and coalescing with these smaller particles. Under these conditions, particles tend to grow in size and settle at still higher downward velocity. This is known as __________ settling.  b. Based on concentration and the tendency of particles to interact, particle settling in a water or wastewater       clarifier can be described as:  a) compression  b) discrete particle settling c) Any or all of these types of settling may occur in a single clarifier d) hindered (also called zone) settling e) flocculent settlin                                                             ?                              ? c. Rectangular clarifiers typically use either chain-and--------- or traveling- ----------type sludge…

(a) A groundwater borehole at USM engineering campus contains 3000 mg/L of TDS. The flow is 0.32 m3 /s. The design TDS concentration of the product water is below 400 mg/L. The net pressure is 40 atm. The membrane manufacturer provides that the membrane has a water flux rate coefficient of 2.2 x 10-6 s/m and a solute mass transfer rate of 1.5 x 10-6 m/s. Calculate the membrane area required for the RO system.   (B)  A water treatment at Nibong Tebal receiving a raw water contains a concentration of 0.5 µg/m3 atrazine from Kerian River. In order to comply with the drinking water quality guideline, the treatment plant should reduce the concentration of Atrazine to 0.1 µg/L. If the dosing of powdered activated carbon have been applied before the coagulation, calculate the minimal dose of PAC in mg/m3 .

At the location of a wastewater discharge, a contaminant is well mixed across a river that is 5 mwide and 1 m deep. The flow in the river is 2 m3/s, the contaminant concentration is 200 mg/L, thelongitudinal diffusion coefficient is 3 m2/s, and the decay constant is 50 d−1. (a) What is the maximum contaminant concentration that is expected at a location 2 km downstream of the wastewater discharge?(b) How would this maximum concentration be affected if the waste discharge is limited to operating for only 30 minutes per day.

Waste activated sludge can be described as a Newtonian fluid with a kinematic viscosity of 20 x 10 ft/sec. At the same temperature, the kinematic viscosity v of water is 10 ft/sec. The relative roughness of the piping system is 0.001. The pressure drop for flow of water at a Reynolds number of 10' in this piping system was determined to be 1.0 psi. If waste activated sludge flows at the same velocity through the piping" system, the pressure drop (psi) is most nearly:

Question 1: True/False questions True or False 1 6 The lower the water turbidity, the higher the allowable scour velocity in sedimentation tank.( ) 2 Coagulation process is the conventional process used to remove color, turbidity and bacteria from water. ( 7 The process in which coagulant is added with to neutralize the negative charge of the colloidal particles and remove the electrical double layer is called compression of electrical double layer ( The required dose of coagulant can be determined by performing jar test. ( ) 3 The axial-flow impeller provides more turbulence 8 and is used for rapid mixing ( ) The process in which high concentration of monovalent cation is added to water to compress the ionic cloud is called sweep coagulation. ( 4 Ferric salts have a wider pH range for effective 9 coagulation than aluminum ( For mixed-media filter the layer of anthracite is used to catch the very fine particles ( ) 5 Water with low turbidity requires more coagulant 10 For filtration…

A mixed liquor sample form an activated sludge plant was settled in a one-litre measuring cylinder for 30 minutes after which time, a volume of 350 m/ of sludge was recorded. When 50 m/ of the mixed liquor were filtered through a GFC paper for the determination of MLSS the gain in weight of the paper was 0.1375 g. Determine the SVI.

H Gy Q#4:The table shows data of a wastewater sample collected from a river with a temperature of 30 °C analyzed for the BODs test. The rate constant is 0.2 day-¹ at the lab temperature (20 C). Find BODs at the river. Initial dissolved oxygen, mg/L 9 What will be the BOD7 at the river? Final dissolved oxygen, mg/L 3.5 Sample volume, ml 35

Given:Flow rate of water = 500 L/minSuspended solids concentration in influent water = 100 mg/LRequired effluent suspended solids concentration = 10 mg/LFiltration rate = 10 m^3/m^2/hrFiltration tank dimensions: Length = 5 m, Width = 3 m, Depth = 4 mCalculate:o Calculate the total suspended solids (TSS) load in the influent water:o Calculate the filtration tank surface area:o Calculate the required filtration tank capacity:o Calculate the required detention time in the filtration tank:   Q2) DisinfectionGiven:Flow rate of water = 2000 m^3/hChlorine residual required in effluent = 0.5 mg/LInitial chlorine concentration in influent water = 2 mg/LChlorine decay rate in disinfection tank = 0.05 per hourDisinfection tank volume = 300 m^3Calculate:o Calculate the chlorine demand in the influent water:o Calculate the chlorine dosage required:o Calculate the chlorine dosage rate:o Calculate the actual chlorine dosage rate considering chlorine decay: