US 2003/0201233 A1 · Process for treating liquid septage

Abstract

A process for treating liquid septage and other biosolids having the steps of placing a known amount of liquid septage in a tank, mixing in a sufficient quantity of alkaline material to raise the pH to a desired level, flocculating the septage, storing the pH adjusted septage for a predetermined period of time, thickening the septage, de-watering the septage, and pasteurizing the resultant liquid effluent and de-watered solids cake. The process for treating liquid septage and biosolids disclosed by the current invention meets the Class A vector attractant reduction and pathogen reduction requirements mandated by the U.S. EPA. The end product of septage and other biosolids treated using the process disclosed by the current invention can be sold as fertilizer, and utilized without any additional permits.

Claims50

Dependent claims

A process for treating liquid septage comprising the steps of:

removing non-organic matter from liquid septage;
adding an alkaline material to said septage;
mixing said alkaline material into said septage until said septage reaches a predetermined pH level;
de-watering said septage;
and
heating the de-watered septage to a predetermined temperature for a predetermined time.

3 more elements

A process for treating liquid septage comprising the steps of:

removing debris, trash, and other non-organic matter from a quantity of liquid septage;
placing said septage into a mixing tank;
selecting an alkaline material from a group comprising quick lime, hydrated lime, limestone, fly ash, wood ash, sodium hydroxide, potassium hydroxide, and kiln dust;
adding an amount of said alkaline material that has been determined based on the quantity of liquid septage, the pH level of said septage, the lime demand of said septage, and the alkalinity of said alkaline material, by continuously circulating a portion of said septage from said mixing tank into a separate tank;
metering said alkaline material into said portion of said septage;
and reintroducing said portion of said septage into said mixing tank;
mixing said alkaline material and said septage until the entire quantity of said septage reaches a pH level of at least 12;
mixing a polymeric flocculent into said septage;
storing said septage for a period of at least 24 hours after said septage is mixed with said alkaline material;
testing said septage at least 2 hours after said septage is mixed with said alkaline material, to ensure that the pH level of said septage is at least 12;
and testing said septage at least 24 hours after said septage is mixed with said alkaline material, to ensure that the pH level of said septage is at least 11.5;
thickening said septage by decanting liquid effluent from said septage;
de-watering said septage by removing the free liquids from the solids in said septage thereby producing de-watered solids;
heating said de-watered solids and said liquid effluent to predetermined temperatures for a predetermined times according to the following equations;
if the percentage of solids is seven or higher, the material is heated to a temperature of at least 50° C. and maintained at that temperature for a period of at least 20 minutes and the temperature and time period shall be determined according to the equation
11 D = 131 , 700 , 000 10 0.1400 ⁢ ⁢ t
where, D is the time in days and t is the temperature in degrees Celsius, but if the percent of solids is less than seven, the material is heated to a temperature of at least 50° C. and maintained at that temperature for a period of at least 30 minutes and the temperature and time period shall be determined according to the equation
12 D = 50 , 070 , 000 10 0.1400 ⁢ ⁢ t
where, D is the time in days and t is the temperature in degrees Celsius;
or if the percent of solids is less than seven, and the material is heated for a period of at least 15 seconds but less than 30 minutes, the temperature and time period shall be determined according to the equation
13 D = 131 , 700 , 000 10 0.1400 ⁢ ⁢ t
where, D is the time in days;
and t is the temperature in degrees Celsius.

20 more elements

Dependencies are inferred from the claim text.

Process for treating liquid septage

Life of this patent

Process for treating liquid septage

Life of this patent

Abstract

Claims50