Organic Waste Recycling

Land treatment of wastewater 435

Overland flow process

The Campbell Soup Company in Paris, Texas, USA, operates a complete line of
heat-processed soups as well as beans and spaghetti products. Its 364-ha
overland flow treatment site is planted with water tolerant grasses, such as reed
canary grass, perennial rye grass, bermuda grass, tall fescue, and native
vegetation (Loehr et al. 1979). The soils at the site are sandy loam, clay, and
clay loam. Study of the fate of the applied wastewater indicates that about 20%
percolates down through the soil, 10-30% is lost by evapo-transpiration, and the
remaining 60% returns to the surface stream as runoff (Loehr et al. 1979). A
sprayed effluent is allowed to flow down 45-60 m slopes ranging from 2 to 6
percent. Grasses are harvested two or three times a year as cash hay crops. The
purified water (or runoff) is discharged to the receiving stream via prepared
waterways. Table 8.14 shows the design, operation and performance data of this
system.
This overland flow system operates as well in winter as in other seasons.
Although the removal of phosphorus was about 42%, a later change in the
operating procedure, to provide a longer rest period between applications with
no change in the total wastewater volume, has increased phosphorus removal to
nearly 90% without affecting the BOD or nitrogen removals.

Table 8.14 Design, operation and performance data of overland flow process of the
Campbell Soup System, Paris, Texas (Loehr et al. 1979; Hinrichs et al. 1980)

Length of slope

Slope

Size of sprinkler nozzles

Distance between sprinklers

Operating pressure at sprinkler heads

Pretreatment

Volume of wastewater treated

Number of months working in a year

Wastewater application rate

Wastewater application schedule

45-60 m

2-6%

6.5 (50 L/min)-8 (80 L/min) mm

25 m

340-480 kPa

Screen and degrease

22,700 m^3 /day

12 months/yr

5-7.6 (cm/wk)

6-8 hr/day on, 16-18 hr/day off

Mean concentration (mg/L) Removal (%)

Parameter

Influent Effluent Concentration Mass (based on

runoff)

TSS

BOD

N

P

263

616

17.4

7.6

16

9

2.8

4.3

93.5

98.5

83.9

42.5

98.2

99.1

91.5

61.5