23 JULY 2003
overflow weir (i.e., V-notch weir) and level sensors to indicate when a stable minimal
flow rate has been achieved. As described previously, this minimum flow rate is often
used in combination with maximum termination pressure as the indicator to end the
For presses not treating HTRW, stored filtrate is typically used as makeup
water for the precoat or prefilling systems, returned to primary treatment processes, or
transferred to subsequent treatment processes prior to disposal. However, for HTRW
applications, because the filtrate has the potential to still contain contaminants, it is
typically only returned to primary treatment processes or transferred to subsequent
treatment processes prior to disposal and not recycled for makeup water for the filter
2-4.10.2 Disposal of Sludge Cake. Common methods of disposing of HTRW or
industrial sludge cake include disposal in landfills and incineration. Other options for
sludge not treated for HTRW and certain industrial sludge include disposal on
agricultural and non-agricultural land. The method of sludge disposal depends on the
type of sludge treatment provided and the chemical characteristics of the sludge after
2-18.104.22.168 Landfills. Landfilling is a sludge disposal practice in which sludge is depos-
ited in a dedicated area, alone or with solid waste, and buried beneath a soil cover.
Sludge disposal in solid waste landfills must comply with the minimum requirements in
40 CFR 258 and any additional state regulations that are more restrictive. Sludge that is
defined as hazardous waste under 40 CFR 261 may be disposed of in RCRA-permitted
landfills. Prior to disposal, the sludge must be treated to meet the requirements
specified in 40 CFR 268.
2-22.214.171.124 Incineration. Incineration is a disposal practice that destroys the organic
pollutants and reduces the volume of sludge. Incineration takes place in a closed device
using a controlled flame.
The advantage of using an incinerator to dispose of sludge is that the volume
of sludge requiring final disposal in a landfill is greatly reduced. The disadvantages of
incineration include high capital and operation and maintenance costs.
New incinerators must meet the New Source Performance Standards (40
CFR 60, Subpart O) promulgated under the Clean Air Act. If the sludge is defined as
hazardous under 40 CFR 261, the incinerator must meet the requirements of 40 CFR
264, Subpart O. Residual ash from the incineration of sludge that is a listed hazardous
waste remains a hazardous waste until it is delisted, and it must be disposed of as a
2-126.96.36.199 Sludge Application to Agricultural Lands. The sludge cake from domestic
sources is often applied to agricultural land to improve the condition and nutrient content
of the soil for agricultural crops. However, this disposal method is not an option for
sludge generated from HTRW waste.