Method of biotreatment for solid materials in a nonstirred surface bioreactor

Abstract

A method of biotreating a solid material to remove an undesired compound using a nonstirred surface bioreactor is provided. According to the method the surface of a plurality of coarse substrates is coated with a solid material to be biotreated to form a plurality of coated coarse substrates. The coarse substrates have a particle size greater than about 0.3 cm and the solid material to be biotreated has a particle size less than about 250 mum. A nonstirred surface reactor is then formed by stacking the plurality of coated coarse substrates into a heap or placing the plurality of coated coarse substrates into a tank so that the void volume of the reactor is greater than or equal to about 25%. The reactor is inoculated with a microorganism capable of degrading the undesired compound in the solid material, and the solid material is then biotreated in the surface bioreactor until the undesired compound in the solid material is degraded to a desired concentration. Preferably the thickness of the solid material coating on the plurality of coarse substrates is less than about 1 mm and the void volume of the reactor is greater than or equal to about 35%. The process is useful for many different biotreatment processes, including the bioremediation of contaminated soils, the desulfurization of coal, and the biooxidation of refractory sulfide ores and concentrates. In bioremediation applications, the undesired compound is typically an organic compound. In coal desulfurization and refractory sulfide ore biooxidation applications, the undesired compound is sulfide minerals.

Description

1. This application is a continuation of co-pending U.S. patent application Ser. No. 09 / 097,316, filed Jun. 12, 1998, by William J. Kohr, which is a continuation of U.S. patent application Ser. No. 08 / 636,117, filed Apr. 22, 1996, which itself is a continuation-in-part of co-pending U.S. patent application Ser. No. 08 / 588,589, filed Jan. 18, 1996, which is a continuation-in-part of co-pending U.S. patent application Ser. No. 08 / 459,621 filed Jun. 2, 1995. Each of the foregoing applications is incorporated herein by reference as if fully set forth.2. 1. Field of the Invention3. The present invention relates to the biotreatment of solid materials. In particular, the present invention relates to the ex situ biotreatment of solid materials in an aerobic process to degrade an undesired compound present in the solid material.4. 2. Description of the Prior Art5. Biological treatment processes are finding application throughout industry. Such processes have been used in waste water treatmen...

AI Technical Summary

Benefits of technology

42. The thickness of the solid material coating on the plurality of coarse substrates is preferably less than about 1 mm to ensure that the microorganism being used in the biotreatment have adequate access to all of the solid material being biotreated. Thicker coatings will increase the capacity of the bioreactor, but the rate at which the biotreatment process advances will be slowed due to the limited access of the microorganism being used to the underlying particles of solid material. To make full use of the capacity of the bioreactor while ensuring adequate microorganism access, the thickness of the solid material coating should be greater than about 0.5 mm and less than about 1 mm. For enhanced air and liquid access, the void volume of the bioreactor can be set to greater than or equal to about 35%. This will greatly improve the rate at which the biotreatment process proceeds.

163. An advantage of using tank 45 over heap 26 for the bioreactor is that it makes separation of the biooxidized concentrate 22 from the substrates 20 easier. After the concentrate 22 is biooxidized to a desired end point, separation of the biooxidized concentrate from the substrates is accomplished by filling the tank with water, and then rapidly draining the tank. The biooxidized concentrate will be carried with the draining water. This process can be repeated several times to improve separation results. Tank 45 is also preferably equipped with a screen in the bottom of the tank which has a mesh size that is less than the size of the substrates, but larger than the concentrate particle size to aid the separation process.

Problems solved by technology

Thicker coatings will increase the capacity of the bioreactor, but the rate at which the biotreatment process advances will be slowed due to the limited access of the microorganism being used to the underlying particles of solid material.

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