380 Organic waste recycling: technology and management
Give reasons about the types of constructed wetlands you plan to choose, and
draw schematic diagram of the constructed wetlands including the hydraulic
profiles.
7.4 A rural household plans to build a 200 m^2 fish pond to raise Tilapia. It
intends to grow duckweeds as fish feed. To produce a fish yield of 110
kg/pond/yr, a duckweed loading of 4 kg dry weight per pond per day is
needed. If the doubling time of duckweed is 10 days, determined the
required area of the duckweed pond. Assume an average duckweed density
of 8 kg (wet weight)/m^2 and a moisture content of 94% for duckweeds.
7.5 You are to visit a floating aquatic weed pond and a constructed wetland unit
being used for wastewater treatment, and determine the first-order kT values,
as shown in Equations 7.4 and 7.11, respectively. Compare the results and
discuss whether the k values of these two systems should be the same or
different.
7.6 If you are to modify Equations 7.4 and 7.11 to encompass other parameters
responsible for wastewater treatment in constructed wetlands or floating
aquatic weed ponds, what are the parameters to be included and how are
these equation to be modified?
7.7 An international space station (ISS) has 10 astronauts and is producing total
wastewater with the following characteristics:
Flow rate = 1 m^3 /day
BOD 5 = 200 g/m^3
Fecal coliforms = 10^3 no./100 mLAssuming that a floating-aquatic-plant system, employing water lettuce (Pistia
stratiotes), is to be used to treat this wastewater on the ISS at the organic
loading rate of 100 kg BOD 5 /(ha-day) and hydraulic retention time of 5 days.
a) Based on the data given in Figure 7.15, determine the dimension (length
× width × depth) required for the floating-aquatic-plant system to be built
on the ISS and the BOD 5 concentration of the treated effluent. Draw a
schematic diagram of this wastewater treatment system to be installed in
the ISS and suggest a possible method to reuse this treated wastewater in
the ISS. Note: Assuming that sunlight is sufficient at the ISS for plant
growth, but there is no gravitational force.