Organic Waste Recycling

388 Organic waste reuse and recycling: technology and management

Table 8.3 Expected quality of treated water from land treatment processesa (U.S. EPA
1981)
Slow rateb Rapid infiltrationc Overland flowd
Constituents Avera
ge

Upper

range

Average Upper

range

Average Upper
range
BOD 5
Suspended solids
Ammonium nitrogen as N
Total nitrogen as N
Total phosphorus as P
Fecal coliforms, no/100
ml

< 2

<1

<0.5

3 e

<0.1

0

<5

<5

<2

<8e

<0.3

<10

5

2

0.5

10

1

10

<10

<5

<2

<20

<5

<200

10

10

<4

5 f

4

200

<15

<20

<8

<10f

<6

<2,000

Units in mg/L unless otherwise noted

a Quality expected with loading rates as the mid to low end of the range shown in Table

8.2.

b Percolation of primary of secondary effluent through 1.5 m (5 ft) of unsaturated soil.

c Percolation of primary or secondary effluent through 4.5 m (15 ft) of unsaturated soil;

phosphorus and fecal coliform removals increase with distance of wastewater flow.

d. Treating comminuted, screened wastewater using a slope length of 30-36 m (100-120 ft).

e Concentration depends on loading rate and crop.

f Higher values expected when operating through a moderately cold winter or when using

secondary effluent at high rates.

In general maximum cost effectiveness for both municipal and industrial

wastewater systems will be achieved by applying the maximum possible amount

of wastewater to the smallest possible land area. This will in turn limit the

choice of suitable vegetation and possibly the market value of the harvested

crop. Optimization of a system for wastewater treatment usually results in the

selection of perennial grasses because of the longer application season, higher

hydraulic loadings, and greater nitrogen uptake, compared to other agricultural

crops. Annual planting and cultivation can also be avoided with perennial

grasses.

Forest systems also offer the advantage of a longer application season and

higher hydraulic loadings than typical agricultural crops, but may be less

efficient than perennial grasses for nitrogen removal depending on the type of

tree, its stage of growth and the general site conditions.