Method of treating wastewater sludges for pathogen removal and vector control

DETAILED DESCRIPTION A method for treating wastewater sludge and biosolids to achieve Class A pathogen reduction standards and to reduce vector attraction, comprising the steps of providing a predetermined amount of dewatered sludge and as a first step, raising the sludge pH to above 12 by adding alkaline reagents such lime, cement, cement kiln dust (ckd), fly ashes, or similar caustic agents.
After base conditioning by adjusting the pH, the sludge is subjected to a sufficiently high level of vacuum (within a few inches of Hg relative to absolute zero pressure) in concert with elevating the temperature to induce osmotic stress, causing the helminth ova egg casings and membranes to rupture, rendering the eggs inviable.
The amount of time and exposure to the low ambient pressure can be varied with the amount of alkaline material utilized for pH elevation in order to reduce bacterial and viral pathogens and for vector control.
Therefore, the combined effect of vacuum and alkaline treatment are mutually reinforcing.
The application of low ambient pressure will be applied continuously during the process, typically by introducing and moving the sludge into an evacuated vessel via a sealing auger arrangement used in deairing pugmills and extruders.
The odors release in the vacuum chamber.
In an alternate embodiment, a high pressure extrusion step, is included.
First,the shear strength of the sludge will be increased by adding a bulking agent such as ground waste paper, gypsum board, tobacco dust and sawdust, to take the very low shear strength typical of most dewatered sludges and raise it to a point where, under an extruder, extreme pressure can be applied, which amounts to additional frictional resistance, thus raising the temperature within the dewatered sludge.
Thus, in this additional step of the process, the sludge is mixed with enough bulking agents to stiffen the sludge to a point where it could be forced through an extrusion die under pressures that are great enough to kill the helminth ova