[Code of Federal Regulations]
[Title 40, Volume 26]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR503.31]

[Page 844-845]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 503--STANDARDS FOR THE USE OR DISPOSAL OF SEWAGE SLUDGE--Table of Contents
 
          Subpart D--Pathogens and Vector Attraction Reduction
 
Sec. 503.31  Special definitions.

    (a) Aerobic digestion is the biochemical decomposition of organic 
matter in sewage sludge into carbon dioxide and water by microorganisms 
in the presence of air.
    (b) Anaerobic digestion is the biochemical decomposition of organic 
matter in sewage sludge into methane gas and carbon dioxide by 
microorganisms in the absence of air.
    (c) Density of microorganisms is the number of microorganisms per 
unit mass of total solids (dry weight) in the sewage sludge.
    (d) Land with a high potential for public exposure is land that the 
public uses frequently. This includes, but is not limited to, a public 
contact site and a reclamation site located in a populated area (e.g, a 
construction site located in a city).
    (e) Land with a low potential for public exposure is land that the 
public uses infrequently. This includes, but is not limited to, 
agricultural land, forest, and a reclamation site located in an 
unpopulated area (e.g., a strip mine located in a rural area).
    (f) Pathogenic organisms are disease-causing organisms. These 
include, but are not limited to, certain bacteria, protozoa, viruses, 
and viable helminth ova.
    (g) pH means the logarithm of the reciprocal of the hydrogen ion 
concentration measured at 25 [deg]Centigrade or measured at another 
temperature and then converted to an equivalent value at 25 
[deg]Centigrade.
    (h) Specific oxygen uptake rate (SOUR) is the mass of oxygen 
consumed per unit time per unit mass of total solids (dry weight basis) 
in the sewage sludge.
    (i) Total solids are the materials in sewage sludge that remain as 
residue when the sewage sludge is dried at 103 to 105 degrees Celsius.
    (j) Unstabilized solids are organic materials in sewage sludge that 
have not been treated in either an aerobic or anaerobic treatment 
process.

[[Page 845]]

    (k) Vector attraction is the characteristic of sewage sludge that 
attracts rodents, flies, mosquitos, or other organisms capable of 
transporting infectious agents.
    (l) Volatile solids is the amount of the total solids in sewage 
sludge lost when the sewage sludge is combusted at 550 degrees Celsius 
in the presence of excess air.

[58 FR 9387, Feb. 19, 1993, as amended at 64 FR 42571, Aug. 4, 1999]