Organic Waste Recycling

Land treatment of wastewater 433

8.6.5 Case studies

The followings are successful case studies for the three-land treatment processes
operated at full-scale in the USA.

Table 8.11 Monitoring program for a large slow-rate system (U.S.EPA 1973)

Frequency analysis

Groundwater

Parameters
Applied
water

Soil Plants

Onsite

wells

Perimet

er wells

Background
wells
Flow C - - - - -
BOD 5 of TOC W - - Q Q Q
COD W - - Q Q Q
Suspended solids W - - - - -
Nitrogen, total W 2A A Q Q Q
Nitrogen, nitrate - - - Q Q Q
Phosphorus, total M 2A A Q Q Q
Coliforms, total W - - Q Q Q
pH D Q - Q Q Q
Total dissolved
solids

M - - Q Q Q

Alkalinity M - - Q Q Q
SAR M Q - Q Q Q
Static water level - -- - M M M
Legend: C = continuously 2A = Two samples per year
D = Daily A = Annually
Q = Quarterly M = Monthly
W = Weekly SAR = Sodium absorption ratio
Note: Wastewater applied and groundwater should be tested initially and periodically
thereafter, as appropriate, for heavy metals, trace organics, or other constituents of
environmental concern.

Slow rate process

The city of San Angelo in Texas, USA, owns and operates a wastewater
irrigation system with an area of 259 ha and a capacity of 1.9x10^4 m^3 /day. The
surface soil is clay and clay loam. A hay crop is grown, which is baled and sold,
and an average of 500 cattle are grazed on the pasture land (Crites and Pound
1976). Primary treatment of the wastewater precedes surface irrigation, and
about 1 week of storage capacity is available when irrigation is not needed.
Operating and performance data of this system are shown in Table 8.12.