Inactivation of microorganisms and virus in liquids and sludge

#Environmental technology and treatment sludge from wastewater treatment plants and the like.

#As public awareness has increased regarding the endangering effects of pathogens in liquids and sludge from wastewater treatment plants, pertinent environmental laws and regulations for the protection of human health have become more stringent. This is particularly true for sludge from wastewater plants to be deposited on agricultural land sites, where the nutrients contained in the sludge are utilized for crop growth. There is a movement towards the banning of Class B sludge (for a definition, see US EPA Code 40 CFR, Part 503) for land applications because of the dangers to human and animal health due to the pathogens contained in Class B sludge. Some counties in California, which receive Class B sludge, have passed legislation banning such land application of Class B sludge, effective Dec. 31, 2002. In order to continue land application in these counties, which is essential for biosolids management programs, Class B sludge must be upgraded to Class A biosolids by removing the existing pathogens. Accordingly, a new economical and efficient process to upgrade Class B sludge to Class A biosolids is needed.

#The quantity of Class B sludge that could be converted to Class A biosolids is enormous. Therefore, facilities to inactivate pathogens and virus in sludge should be able to handle these large quantities. This requirement limits the number of technologies available.

#The invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements, and in which:

#FIG. 1 is a block diagram illustrating a treatment method in accordance with one embodiment.

#FIG. 2 is a schematic diagram of an apparatus used to inactivate pathogens in wastewater sludge in accordance with one embodiment.

#One embodiment relates to reducing the cost of inactivating bacteria and virus present in Class B sludge (EPA rule 40 CFR, Part 257 and 503) produced at wastewater treatment plants and used for land application. Sewage sludge may contain the human health endangering bacteria Fecal Coliform and/or Salmonella sp., Enteric Virus and/or Helminth Ova.

#FIG. 1 is a block diagram illustrating a treatment method in accordance with one embodiment. A material containing pathogens, such as sewage sludge, is pumped to a tank or reservoir 100. If the sludge to be treated contains debris and/or rocks, they may be removed prior to treatment by sifting or screening (not shown). This may be accomplished by a conventional mechanical operation that separates the debris, rocks, etc., from the sludge. If the debris and rocks are contaminated, the debris and rocks may then be properly disposed of in accordance with any applicable state and federal law. The remaining contaminated material enters inactivator 110, in one embodiment, a machine for treatment of liquids, where pathogens contained in a liquid, or contained in a quasi-liquid matter, such as sewage sludge from wastewater treatment plants, may be exposed to, and inactivated by an intense alternating mechanical stress and strain field, at sonic and/or ultrasonic frequencies. In one embodiment, cavitation is produced and sustained in the contaminated material along spiral-shaped paths between two or more disks which rotate at high RPM.

#Treating Class B sludge from wastewater treatment plants, the pathogens contained in such sludge may be inactivated below detectable levels, thus upgrading the Class B sludge to Class A biosolids. The Class A material is drained out and pumped to a storage tank or reservoir 120, or may be dewatered by a decanter 130, or any other adequate means, to, for example, greater than 27 percent solid content, in order to reduce the weight and/or volume for transportation to land application sites or other methods of disposal. The Class A biosolids are available for pick up by any means of hauling or transportation from the staging area 140, or from the reservoir 120, respectively.