The sludge produced from the aeration tank of the activated sludge process has a solid content of 2% (by weight) is introduced in sludge thickener, where the sludge volume is reduced to half. Assuming that the amount of solid in supernatant from the thickener is negligible, the specific gravity of sludge solids is 2.2 and density of water is 1000 kg/m3 and density of sludge is 1011 kg/m3. What is the solid content (by weight) of the thickened sludge? 4.24% 3.36% 4% 3.96%

A wastowater sample of 100 ml. was filtered through the filter paper and the filtered wator was collected in a beaker. Based on the information provided in Table 1, calculato total solids, suspended solids, dissolved solids in wastowater (mg/1.). Table 1: Description Weight of filter paper (gm) Weight of tilter paper +solids (gm) after oven dry at 105 'C Weight of filter paper +solids (gm) after oven dry at 105 C Weight of beaker (gm) Weight of beaker + water after oven-dried at 105 "C (qm) Weight 0.05 0.1 7.76 50 51.5 O Suspended solids - 76.6 mg/; dissolved solids 15 mg/ and Total solids 91.6 mg/ Suspended solids 86.6 mg/L; dissolved solids - 15 mg/L and Total solids - 101.6 mg/ Suspended solids - 76.6 mg/L; dissolved solids = 10 mg/L and Total solids - 86.6 mg/L Suspended solids 70.6 mg/L; dissolved solids = 25 mg/L and Total solids = 95.6 mgt.

1. A CM reactor receives influent containing 10 mg/L of tracer dye for 2 hours. The tracer addition is terminated but the flowrate of water is maintained. The volume of the reactor is 10 L and the flowrate is 2 L/hr. What is the concentration of tracer in the reactor 1 hr after the dye addition is terminated? The reactor had an initial concentration of tracer of 1 mg/L when the tracer addition commenced.

A 2-tank Step Aeration Activated Sludge (SAAS) system has the following characteristics: V1 V2 Q Waste Recycle Oxygen demand (L) (L) (L/min) Ratio Ratio of Cells 500,000 450,000 100 0.45 0.5 1.2 Xv1 Xv2 Xd1 Xd2 SO S1 S2 Xrv Xrd (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 1500 ☐ 14 1400 200 150 150 10 2 2000 1000 1. What is the mean cell residence time and hydraulic residence time in days? 2. Write the mass balance equation for required oxygen in tank #1. 3. What is the oxygen requirement for tank #1 in kg/day? (equation will be in units of mg/min)

2. Domestic "tap" water generally has a conductivity in the range 0.5 - 1.0 ms/cm. Based on your experimental results in Part A, offer an explanation on the difference in conductivity of deionized (DI) water and tap water.

A bio-tower composed of a modular plastic medium of 6 m is used as secondary treatment component in a municipal wastewater treatment plant. Flow from the primary clarifier is 25000 m³/day with 200 mg/1 BOD. The treatability constant is 0.06 per min. To produce an effluent with a soluble BOD of 20 mg/1, the surface area as per Eckenfelder (coefficient related to medium is 0.5) is approximately:

An ion exchange softener of 5 m3 volume is used to treat the raw water for a community. The absorptive capacity of medium is 90 kg/m3 at particular flow rate. The rate of flow from source is 25000 m3 /day. Determine the limiting hardness in treated water if ion exchanger softener is regenerated on daily basis

Biomass and substrate mass balance equations can be merged giving QwXR/VX=Y/X (Qo/V) (So-S)-kd (i) Prove that X= SRT/HRT Note that HRT = t and SRT = tc. (ii) If you are an engineer working in a wastewater consultancy company, and obtained the following data: - SRT = 20 days HRT 20 hours = (Y(So-S)/1+kd(SRT)). So = 350 mg/L S = 100 mg/L Y = 0.15 kd = 0.22 per day Calculate the increment of MLSS (%) required in the aerobic tank if the discharge BOD5 in the effluent needs to achieve 10 mg/L.

the TOC of a wastewater sample is 75mg/L. what is the ultimate BOD of the sample. The organic matters in the sample are assumed completely degradable.

2. The suspended solids content is determined by filtering a portion of the sample through a glass-fiber filter disk, drying the disk at 105°C, and igniting the residue by placing the dried sample in a muffle furnace at static (?). The following masses are recorded: • Volume of sample: 30 mL • Mass of filter disk: 0.1170 g a) The total suspended solids content is: b) The volatile suspended solids content is: Mass of disk and dry solids: 0.1278 g Mass of disk and ignited solids: 0.12489 g c) The fixed suspended solids content is: