Develop your knowledge of key principles relating to

Question

(a) Develop your knowledge of key principles relating to wastewater system design

(b) to develop technical competence in problem formulation and solution in this discipline area, and

(c) to improve your teamwork and technical communication skills, with particular emphasis on presentation and setting out solutions.)

Part A will be the estimation wastewater flows and Part B will be the design of trickling filter-activated sludge system.

PART A: Estimation of Wastewater Flows

Data on the expected saturation population densities and wastewater flows for the various types of housing in the New Park Development (Figure 1) were derived from the actual records of similar nearby developments and are given in the table (Table 1). The flowrate allowances for the commercial (including the shopping area) and industrial wastewater were estimated to be 25 and 35 m³/(ha.day) respectively.

Figure 1: Classification of land use

On the basis of actual flow records of similar activities, the average peak factors are 2 for the commercial flows and 2.5 for the industrial flows. The planned school within the New Park Development is to serve 2500 students at ultimate capacity. The average flow is 80 L/(student. day), and the peak factor for the school is 4.0.

Assume the average park attendance is 300 persons/day and the flow is 70 L/person.d.  The peaking factor for the park is 4.0. Estimate the expected average and peak wastewater flows from the New Park development at the end of full development.

PART B: Designing of Trickling Filter (TF) /Activated Sludge (AS) Systems

A TF/AS process is used after primary clarification and the primary effluent wastewater characteristics are given below (Table 2). For the following design parameters, compare the effect of designing the plastic tower trickling filter for 40 percent versus 75 percent BOD removal:

1. Trickling filter diameter (m) and hydraulic application rate (L/m².s)

2. Oxygen required in the activated -sludge aeration tank (kg/d)

3. The amount of solids wastes per day (kg/d)

4. The volume (m³) and hydraulic retention time (h) of the aeration tank.

Use the following assumptions for the trickling filter and activated sludge design.

Trickling Filter:

Plastic packing treatability coefficient, k₂₀ = 0.18 (L/s)^0.5/m²

Packing depth = 6.1 m

Number of towers = 2

50 percent of theoretical effluent BOD is soluble

Activates sludge:

SRT = 5.0 day (no nitrification)

MLSS = 3000 mg/L

Biomass yield , Y = 0.6 g VSS/g BOD removed

Endogenous decay, k_d = 0.12 g VSS/g VSS.d

UBOD/BOD = 1.6