Method for evaluating bioavailability of organic solid waste by anaerobic conversion based on fractal dimension

Patent metadata

Field	Value
Publication number	US-11156539-B2
Application number	US-202017109300-A
Country	US
Kind code	B2
Filing date	Dec 2, 2020
Priority date	Dec 2, 2019
Publication date	Oct 26, 2021
Grant date	Oct 26, 2021

Abstract

Provided is a method for evaluating a bioavailability of organic solid waste by an anaerobic conversion based on fractal dimension, relating to anaerobic digestion of organic solid waste. Organic solid waste is broken up and dried, and the organic solid waste is analyzed using a laser particle size analyzer, so as to measure a wave vector Q and a scattering intensity I. The wave vector Q and the scattering intensity I are analyzed using a data processing software, and a two-dimensional fractal dimension Df is obtained based on a fractal theory. A volatile fatty acid maximum VFAmax and a biochemical methane potential BMP of the organic solid waste are predicted according to the two-dimensional fractal dimension Df, so as to evaluate a bioavailability of organic solid waste by an anaerobic conversion.

First claim

What is claimed is:

1. A method for evaluating a bioavailability of organic solid waste by an anaerobic conversion based on fractal dimension, comprising:
1) collecting a sample of the organic solid waste, and drying and breaking up the sample to obtain a dried sample;
2) adding water into the dried sample obtained in step (1) followed by stirring to obtain a mixture;
3) analyzing the mixture obtained in step (2) using a laser particle size analyzer, so as to measure a wave vector Q and a scattering intensity I of the mixture;
4) analyzing the wave vector Q and the scattering intensity I obtained in step (3) using a data processing software to obtain a two-dimensional fractal dimension D f of the sample according to a formula I∝Q −D f ;
5) collecting and inputting the two-dimensional fractal dimension D f , and corresponding maximum volatile fatty acid (VFA max ) or biochemical methane potential (BMP) into the data processing software to obtain data points; and fitting the data points using linear regression to obtain a calculation model of VFA max or BMP with respect to the fractal dimension D f ; and
6) plugging the fractal dimension D f of the sample into calculation model obtained in step (5) to obtain the VFA maX or the BMP of the sample, so as to evaluate the bioavailability of the organic solid waste based on values of the VFA maX or the BMP;
wherein in step (4), the formula I∝Q −D f is an equation I=k·Q −D f , wherein k is a slope;
both sides of the equation take natural logarithm to obtain: 1nI=1n(k·Q −D f ); then the equation is simplified as: 1n I=−D f 1n Q+1n k; the I and Q obtained in step (3) take the natural logarithm to obtain the lnI and lnQ which are taken as a dependent variable and an independent variable of the equation, respectively, and the fractal dimension D f of the sample is obtained using the linear regression;
in step (5), the calculation model of the VFA max or the BMP with respect to the fractal dimension D f is expressed as:
Y=A-BX,
wherein X is the fractal dimension D f ; Y is the VFA max or the BMP of the sample; and A and B are coefficients of the calculation model of the VFA max or the BMP; and
in step (6), the VFA max is a maximum cumulative value of a volatile organic acid in a hydrolysis acidification process without methane production; the BMP is a maximum potential for bioconversion of organic matter in the sample into methane in an anaerobic process; and the higher the values of the VFA max or the BMP are, the higher the bioavailability is.

2. The method of claim 1 , wherein in step (1), the sample is organic solid waste pretreated by different treatment methods, organic solid waste collected from different areas, organic solid waste of different kinds or organic solid waste collected at different times.

3. The method of claim 2 , wherein the sample is broken up to 0.01-3500 μm.

4. The method of claim 1 , wherein in step (2), the sample is diluted with pure water in a container to obtain the mixture with a solid content less than 5%; the mixture is fully stirred by an external magnetic stirrer having a magnetic stirring bar; and the container and the magnetic stirring bar are cleaned and dried before use.

5. The method of claim 1 , wherein in step (3), a light source of the laser particle size analyzer is a helium-neon laser emitting at 633 nm; a refractive index of a dispersant is 1.330; an absorption rate of particles in the dispersant is 0.100; a density of the dispersant is greater than 1; the dispersant is water; time for a background measurement is 10 s; time for measuring the mixture is 10-12 s; time for measuring the mixture with uneven dispersion is 10-20 s; the mixture is measured 3 times; during a measurement, a shading range of the mixture containing particles having a diameter of tens of microns is 10-20%; a shading range of the mixture containing particles having a diameter of a few microns is 6-10%; a shading range of the mixture containing particles have a diameter of hundreds of nanometers is 4-6%; a shading range of the mixture with uneven dispersion is 10-20%; a stirring speed is 2000-3000 r/min; and after the mixture is measured, a cleaning system of the laser particle size analyzer is operated.

Assignees

• Univ Tongji

Inventors

• Dai Xiaohu
• Hua Yu
• Cai Chen

Classifications

• G01N2015/0053

  in liquids, e.g. trouble · CPC title

• G01N15/0205 Primary

  by optical means · CPC title