On-Site Wastewater Treatment and Disposal Systems - Forced ...

the bubble diffuser units to lo-30 set in packed columns and PPI systems
(59)(60). Limited data are currently avail able on long-term use of
these contactor devices for onsite systems. There are relatively few
field-tested, small-capacity systems commercially available.
6.5.4.4 Operation and Maintenance
The ozone disinfection system is a complex series of mechanical and
electrical units, requiring substantial maintenance, and is susceptible
to a variety of malfunctions. Since data on long-term experience are
relatively unavailable, it is not possible to assess maintenance re-
quirements on air cleaning equipment, compressors, cooling and drying
equipment, and contactors. It is estimated that 8 to 10 kWh/lb of ozone
generated will be required (54). Monitoring requirements are similar to
those for UV disinfection, including occasional bacterial analyses and
routine ozone monitoring.
6.6 Nutrient Removal
6.6.1 Introduction
6.6.1.1 Objectives
Nitrogen and phosphorus may have to be removed from wastewaters under
certain circumstances. Roth are plant nutrients and may cause undesir-
able growths of plants in lakes and impoundments. Nitrogen may also
create problems as a toxicant to fish (free ammonia), as well as to ani-
mals and humans (nitrates). In addition, the presence of reduced nitro-
gen may create a significant oxygen demand in surface waters.
Nitrogen may be found in domestic wastewaters as organic nitrogen, as
ammonium, or in the oxidized form as nitrite and nitrate. The usual
forms of phosphorus in domestic wastewater include orthophosphate, poly-
phosphate, pyrophosphate, and organic phosphate. Sources of wastewater
nitrogen and phosphorus from the home are presented in Table 4-4.
The removal or transformation of nitrogen and phosphorus in wastewaters
has been the subject of intensive research and demonstration over the
past 15 to 20 yr. Excellent reviews of the status of these treatment
processes can be found in the literature (61)(62). As discussed in
Chapter 7, the soil may also. serve to remove and/or transform the
nitrogen and phosphorus in wastewaters percolating through them.
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