Biosolids generated at the Southwest Clean Water Plant meet the most stringent federal and state regulations for pollutants.

Biosolids Pollutant Levels & Regulated Limits

Metal	2013 SWCWP Biosolids Average mg/kg	Exceptional Quality mg/kg	Ceiling Concentration mg/kg
Arsenic	<4.00	41.0	75.0
Cadmium	2.20	39.0	85.0
Chromium	38.0	1,200	3,000
Copper	376	1,500	4,300
Lead	46.9	300	840
Mercury	0.93	17.0	57
Molybdenum	37.5	18.0	75
Nickel	34.0	420	420
Selenium	<5	36.0	100
Zinc	1,054	2,800	7,500

Note: Exceptional Quality and Ceiling Concentration categories are based on U.S. EPA and Missouri DNR regulation limits.

Nitrogen & Phosphorus Content of Biosolids

Nutrient	Average %
Ammonia	1.20
Nitrate	0.01
Total Kjeldahl Nitrogen	7.00
Total Phosphorus	3.50

Note: Average % data for 2013 dewatered biosolids applied to agriculture land.

Table Explanation
Nitrogen is essential for plant growth. However, excess nitrogen not utilized by plants can leach into groundwater. Nitrogen exists in different forms in the soil. Ammonia is the form most readily available for uptake by plants. In the above table, the percentages for nitrate and nitrite, TKN (Total Kjeldahl Nitrogen), and Ammonia are used for compliance with the Missouri DNR regulations which require calculation of crop nitrogen needs and availability of nitrogen in biosolids applied to land.

Phosphorus is also essential for plant growth, but in excess can be detrimental to the health of lakes and rivers. See the Phosphorus page for more details.