Waste Water Pollution Levels from a primary treatment lagoon in Mexico

Water  quality out of a primary treatment lagoon in Mexico receiving waste from the city of Ojinaga show extremely high Fecal Coliform counts and a large amount of biological material  in the water with a high BOD (28.6-42.5 mg/l). The BOD levels in clean rivers are around 5 mg/l. After the water was discharged from the lagoon and pasted through an oxbow section of the delivery channel, both the fecal coliform and BOD decreased to the levels that  the water could be applied through a trickle irrigation system to irrigate trees without plugging the trickle irrigation system as long as the system has proper design and operation.

Table 1. Selected chemical characteristics for the irrigated wastewater.










Electrical Conductivity (EC)

2.9-3.4 ds/m

2.7-3.1 ds/m

Total Dissolved Solids (TDS)

2167-2670 mg/l

1948-2217 mg/l

Sodium Adsorption Ratio (SAR)



Fecal Coliform

4-800 CFU per 100 ml

230,000-640,000 CFU per 100 ml

Biochemical Oxygen Demand (BOD5)

13.2-14.6 mg/l

28.6-42.5 mg/l

Chemical Oxygen Demand (COD)

67-99 mg/l

100-117 mg/l

Kjeldahl N

5.4 16 mg/l

14.1-37 mg/l


795-1079 mg/l

729-1067 mg/l


240-284 mg/l

201-233 mg/l




Source of this data: New Mexico State University-Ojinaga Pilot Study.

CFU: Colony forming units.