CN103235085A - Method for rapidly determining volatile fatty acid concentration in anaerobic reactor - Google Patents

Abstract

The invention provides a method for rapidly determining volatile fatty acid (VFA) concentration in an anaerobic reactor. According to the invention, according to charge balance and final-initial volumes of a solution requiring detection when two different pH points are established, the relationship between VFA and pH is calculated; and through an acid titration method, VFA concentration of the solution requiring detection can be calculated. The invention provides a method for rapidly determining volatile fatty acid (VFA) concentration in the anaerobic reactor. The method is fast, stable, accurate, simple, and the like. With the method, defects such as rough method and poor accuracy of a colorimetric method and a distillation method are solved, and defects of high cost and complicated operation of a chromatographic method are avoided. With the method, VFA rapid and precise on-line detection can be realized.

Description

The method of volatile fat acid concentration in a kind of quick mensuration anaerobic reactor

Technical field

The present invention relates to the biological wastewater treatment technology field, be specifically related to the method for volatile fat acid concentration in a kind of quick mensuration anaerobic reactor.

Background technology

Volatile fatty acid (Volatile fatty acid VFA) refers to that carbon atom is 1～6 fatty acid, in municipal effluent/mud based on acetic acid, propionic acid, butyric acid.Product acid and the methanogenesis of the normal service requirement system of anaerobic technique are in mobile equilibrium to keep pH constant (6.6～7.4) in the reactor.Otherwise the VFA accumulation makes the pH value cross the low system that will cause and moves failure.Because have multiple buffer system in the anaerobic reactor, buffer action makes that the accumulation of VFA in to a certain degree can not in time be reflected at pH.Therefore quick and precisely measure VFA concentration and become anaerobic reactor operation control more efficient methods

The method of measuring VFA concentration at present mainly contains the way of distillation, colourimetry, vapor-phase chromatography and titrimetry.But first three method not only needs the long period, and needs specific equipment and experienced operator, and therefore being used for fast, accurately measuring VFA has certain difficulty.Titrimetry is fairly simple a, method fast comparatively speaking, Many researchers has developed different titration programs and has measured VFA, mainly contain: Dilallo and Albertson, Mcghee, Nordmann, Colon, Kapp, Ripley et al, Powell and Archer, Moosbrugger et al., Bisogni et al..Wherein researcher such as Moosbrugger propose 5

The step titrimetry is the method for an outbalance, be subjected to other researcher and paid attention to (Moosbrugger.et al.A5-point titration method to determine the carbonate and SCFA weak acid/bases in a queous solution containing also known concentrations of other weak acid/bases.Water SA widely, 1993,19:29-39).Researchers such as Lahar have done improvement in various degree to 5 step titrimetrys, make and measure more quick and accurate (the Lahar.et al.Arapid simple and accurate method for measurement of VFA and carbonate a-lkalinity in anaerobic reactors.Environmental Science﹠amp of VFA; Technology, 2002,36:2736-2741.).But the titrimetry of reporting in the document existed two comparatively general problems in the past.The one, in titration process, to stir the CO that dissolves in the sample ₂Since will with airborne CO ₂Balance more or less has certain loss, has caused the variation of total inorganic carbon (TIC) in the sample, makes that measuring degree of accuracy descends; The 2nd, in order to reduce the interference of other weak acid alkali in the solution (as phosphoric acid etc.) buffer system, often need to determine in advance its concentration, this has increased the complicacy of experiment undoubtedly.

Summary of the invention

In order to address the above problem, the invention provides the method for volatile fat acid concentration in a kind of quick mensuration anaerobic reactor.

In order to realize purpose of the present invention, the invention provides the method for volatile fat acid concentration in a kind of quick mensuration anaerobic reactor, this method charge balance and whole initial body of solution to be measured when setting up two different pH points is long-pending, release the relation between VFA and the pH, and then calculate the concentration of solution VFA to be measured by acidimetry.

Particularly, the step of this method is as follows:

(1) under room temperature state, the volume of getting in the anaerobic reactor is V ₀Solution to be measured, and set initial pH value respectively and be respectively pH ₀And pH ₁

(2) be V with volume _xThe described solution to be measured of acid solution titration, be pH until this pH value of solution value to be measured ₁, this moment, the cumulative volume of described solution to be measured was V ₁

(3) the VFA concentration of the described solution to be measured of calculating, computing formula is as follows:

$C_{\mathrm{VFA}}=\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({\left[H^{+}\right]}_1-K_W/{\left[H^{+}\right]}_1)*V_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0)}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*V_1/V_0}$

In the formula:

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

K _a--the dissociation constant of-----VFA; [H ⁺] ₀=10 ^-pH0Mol/L; [H ⁺] ₁=10 ^-pH1Mol/L;

K _w--the ion-product constant of-----water; V _X--the volume (L) of-----adding acid solution;

C _Acid--the concentration (mol/L) of-----acid solution.

Preferably, described acid solution is hydrochloric acid or sulfuric acid.

Preferably, described pH ₀And pH ₁It is positive and negative 1 that span should select the pk value of VFA to add, described pH ₀And pH ₁Difference greater than 0.2, be preferably 0.5.

VFA concentration computing formula of the present invention is as follows:

In anaerobic system, there is multiple zwitterion, mainly contains VFA ion, hydrogen ion, hydroxide ion, carbanion, bicarbonate ion, dihydrogen phosphate, phosphoric acid one hydrogen root, phosphate anion, sulphur hydrogen radical ion, sulphion, ammonium radical ion, halide ion and each metal ion species.

In multiple weak acid alkali (salt) buffer system in anaerobic system, the pK of carbonic acid ₁=6.36, pK ₂=10.25, the pK of sulfuretted hydrogen ₁=7.04, pK ₂=11.96, the dissociation constant of ammonium root is pK ₁=9.25.As can be seen, pH is more low, and the ability that these weak acid alkali (salt) are accepted proton is more poor, and is more little to the influence of titration.So two pH points that this method is selected are respectively 4.70 and 4.20, in this pH scope, can not consider the influence of above-mentioned weak acid alkali (salt).

Get 0.04L solution to be measured, under electromagnetic agitation, with concentration be the hydrochloric acid solution titration of 0.05M to pH=4.70, drip fast 0.7mL/min, record overall solution volume V to be measured ₀Charge balance in the system is as follows at this moment:

[H ⁺] ₀+n[M ⁿ⁺]=[VFA ^-] ₀+[OH ^-] ₀+[H ₂PO ₄ ^-] ₀+2[HPO ₄ ^2-] ₀+3[PO ₄ ^3-] ₀+[X ^-] ₀ ①

M ^N+---the n valence metal ion

X ^----halide ion

Keep electromagnetic agitation, continue to add hydrochloric acid to pH=4.20 to drop to be measured the hydrochloric acid volume V that record drips with identical speed _XWith overall solution volume V to be measured ₁Charge balance in the system becomes at this moment:

[H ⁺] ₁+n[M ⁿ⁺] ₁=[VFA ^-] ₁+[OH ^-] ₁+[H ₂PO ₄ ^-] ₁+2[HPO ₄ ^2-] ₁+3[PO ₄ ^3-] ₁+[X ^-] ₁ ②

From pH4.70 to 4.20, though the concentration of phosphoric acid, phosphoric acid one hydrogen root, dihydrogen phosphate, phosphate anion changes in the solution, total phosphorus is constant.Therefore represent the concentration of various phosphate anions with total phosphorus, formula 1. deformable is:

$T_P/V_0=\frac{[{H^{+}]}_0-{\left[\mathrm{VFA}\right]}_0-{\left[{\mathrm{OH}}^{-}\right]}_0}{f_1\left({\left[H^{+}\right]}_0\right)}$ ③

$f_1\left({[H}^{+}\right])=\frac{1}{1+K_2/\left[H^{+}\right]+{[H}^{+}]/K_1+K_2*K_3/{\left[H^{+}\right]}^2}+\frac{2}{1+{\left[H^{+}\right]}^2/K_1*K_2+\left[H^{+}\right]/K_2+K_3/\left[H^{+}\right]}$

$+\frac{3}{{\left[H^{+}\right]}^2/K_2*K_3+\left[H^{+}\right]/K_3+1+{\left[H^{+}\right]}^3/K_1*K_2*{\mathrm{<figure-callout\; id="3"\; label="K"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">K</figure-callout>}}_3}$

T _P------total amount (mol) of phosphorus in the sample

K ₁, K ₂, K ₃--one, two, three dissociation constant of-----phosphoric acid

Formula 2. deformable is:

$T_P/{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1=\frac{[{H^{+}]}_1-{\left[\mathrm{VFA}\right]}_1-{\left[{\mathrm{OH}}^{-}\right]}_1}{f_1\left({\left[H^{+}\right]}_1\right)}$ ④

In like manner, the total amount of VFA is constant in the solution, and namely VFA concentration can be expressed as when pH4.70 and pH4.20:

${\left[{\mathrm{VFA}}^{-}\right]}_0=\frac{C_{\mathrm{VFA}}*K_a}{{\left[H^{+}\right]}_0+K_a}$ ⑤

${\left[{\mathrm{VFA}}^{-}\right]}_1=\frac{C_{\mathrm{VFA}}*K_a}{{\left[H^{+}\right]}_1+K_a}$ ⑥

C _VFA--------be initial VFA concentration (mol/L) in the sample;

K _a--the dissociation constant of-----VFA

By formula 3., 4. as can be known:

(①*V ₀)=(②*V ₁) ⑦

With formula 5., 6. 7. substitution can obtain in the sample initial VFA concentration:

$C_{\mathrm{VFA}}=-\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0)*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({{\left[H^{+}\right]}_1-K}_W/{\left[H^{+}\right]}_1)*V_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*V_1/V_0}$

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

[H ⁺] ₀=10 ^-4.7mol/L

[H ⁺] ₁=10 ^-4.2mol/L

K _w--the ion-product constant of-----water;

V _X-------adding hydrochloric acid volume (L)

C _Acid--the concentration (mol/L) of-----hydrochloric acid

In the measurement, sample need not pre-treatment, can realize online detection, and is convenient, fast.

Beneficial effect of the present invention is as follows:

The present invention has set up the method for volatile fatty acid (VFA) concentration in a kind of quick mensuration anaerobic reactor, it has fast, stable, accurate, easy etc. characteristics, colourimetry, way of distillation method is coarse, accuracy is not high shortcoming had both been solved, avoided the deficiency of chromatography cost height, complicated operation again, made the VFA can realize online detection fast, accurately.

Description of drawings

Fig. 1 is embodiments of the invention 6 process flow diagrams.

Mark is as follows among the figure:

Anaerobic reactor 1, water outlet storage bottle 2, pump 3, magnetic agitation instrument 4, pH electrode 5, titrator 6, computer 7.

Embodiment

Introduce the present invention in detail below in conjunction with accompanying drawing and embodiment thereof.But protection of the present invention orientation is not limited to following example, should comprise the full content in claims.

Embodiment 1:

Under room temperature state, dispose phosphate concn respectively and be 0,1,3,6mM, acetic acid concentration is artificial each 0.04L of synthesis reactor water outlet of 5mM.

1. in the 300rpm electromagnetic agitation, dripping speed be under the condition of 0.7mL/min, to phosphate concn be drip in the water outlet of 0mM concentration be 0.05M hydrochloric acid solution to pH be 4.7, record volume (V at this moment ₀=42.15*10 ^-3L).Continuing the hydrochloric acid solution titration with 0.05M, is 4.2 until system pH, and the hydrochloric acid consumption is V _x=9.85*10 ^-4L, the maximum 20min consuming time of process.

Use computing formula of the present invention:

$C_{\mathrm{VFA}}=\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({\left[H^{+}\right]}_1-K_W/{\left[H^{+}\right]}_1)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0)}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0}$

In the formula: V ₁=V ₀+ V _x

[H ⁺] ₀=10 ^-4.7mol/L

[H ⁺] ₁=10 ^-4.2mol/L

K _w--ion-product constant of-----water, 10 ^-14(25 ℃)

V _X-------adding hydrochloric acid volume (L) is 9.85*10 ^-4

C _Acid--concentration (mol/L) of-----hydrochloric acid is 0.05;

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

The final concentration that gets acetic acid is 4.835mM;

2. same operation process, the phosphate concn that calculates with the present invention are 1,3, acetate concentration is respectively 4.894mM, 4.915mM, 5.213mM in the artificial synthesis reactor water outlet of 6mM.

As can be known from the results, the maximum relative error by the resulting acetate concentration of the present invention and actual value is 4.26%, and minimum is 1.7%, and this explanation the present invention is not influenced by phosphate, and method is reliable, the accuracy height.

Embodiment 2:

Under room temperature state, dispose ammonium salt concentration respectively and be 0,1.5,3,4mM, acetic acid concentration is artificial each 0.04L of synthesis reactor water outlet of 1mM.

1. in the 300rpm electromagnetic agitation, dripping speed be under the condition of 0.7mL/min, to ammonium salt concentration be drip in the water outlet of 0mM concentration be 0.05M hydrochloric acid solution to pH be 4.7, record volume (V at this moment ₀=40.53*10 ^-3L); Continuing with concentration is the hydrochloric acid solution titration of 0.05M, is 4.2 until system pH, and the hydrochloric acid consumption is V _x=2.16*10 ^-4L, the maximum 20min consuming time of process.

Use computing formula of the present invention:

$C_{\mathrm{VFA}}=\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({\left[H^{+}\right]}_1-K_W/{\left[H^{+}\right]}_1)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0)}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0}$

In the formula: V ₁=V ₀+ V _x

[H ⁺] ₀=10 ^-4.7mol/L

[H ⁺] ₁=10 ^-4.2mol/L

K _w--ion-product constant of-----water, 10 ^-14(25 ℃)

V _X-------adding hydrochloric acid volume (L) is 2.16*10 ^-4

C _Acid--concentration (mol/L) of-----hydrochloric acid is 0.05.

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

The final concentration that gets acetic acid is 0.931mM.

2. same operation process, the ammonium salt concentration that calculates with the present invention are 1.5,3, acetate concentration is respectively 1.01mM, 0.98mM, 1.00mM in the artificial synthesis reactor water outlet of 4mM.

As can be known from the results, the maximum relative error by the resulting acetate concentration of the present invention and actual value is 6.9%, and minimum is 0%, and this explanation the present invention is not influenced by ammonium salt, and method is reliable, the accuracy height.

Embodiment 3:

Under room temperature state, dispose sulphion concentration respectively and be 0,1,3,6mM, acetic acid concentration is artificial each 0.04L of synthesis reactor water outlet of 1mM.

1. in the 300rpm electromagnetic agitation, dripping speed be under the condition of 0.7mL/min, to ammonium salt concentration be drip in the water outlet of 0mM concentration be 0.05M hydrochloric acid solution to pH be 4.7, record volume (V at this moment ₀=40.54*10 ^-3L); Continuing with concentration is the hydrochloric acid solution titration of 0.05M, is 4.2 until system pH, and the hydrochloric acid consumption is V _x=2.23*10 ^-4L, the maximum 20min consuming time of process.

Use computing formula of the present invention:

$C_{\mathrm{VFA}}=\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({\left[H^{+}\right]}_1-K_W/{\left[H^{+}\right]}_1)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0)}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0}$

In the formula: V ₁=V ₀+ V _x

[H ⁺] ₀=10 ^-4.7mol/L

[H ⁺] ₁=10 ^-4.2mol/L

K _w--ion-product constant of-----water, 10 ^-14(25 ℃)

V _X-------adding hydrochloric acid volume (L) is 2.23*10 ^-4

C _Acid--concentration (mol/L) of-----hydrochloric acid is 0.05;

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

The final concentration that gets acetic acid is 0.942mM.

2. same operation process, the sulphion concentration that calculates with the present invention are 1,3, acetate concentration is respectively 0.946mM, 0.958mM, 1.00mM in the artificial synthesis reactor water outlet of 6mM.

As can be known from the results, the maximum relative error by the resulting acetate concentration of the present invention and actual value is 5.8%, and minimum is 0%, and this explanation the present invention is not influenced by sulphion, and method is reliable, the accuracy height.

Embodiment 4:

Under room temperature state, dispose magnesium hydrogen salt concentration respectively and be 0,2.5,5,8mM, acetic acid concentration is artificial each 0.04L of synthesis reactor water outlet of 5mM.

1. in the 300rpm electromagnetic agitation, dripping speed be under the condition of 0.7ml/min, to magnesium hydrogen salt concentration be drip in the water outlet of 0mM concentration be 0.05M hydrochloric acid solution to pH be 4.7, record volume (V at this moment ₀=42.10*10 ^-3L); Continuing with concentration is the hydrochloric acid solution titration of 0.05M, is 4.2 until system pH, and the hydrochloric acid consumption is V _x=9.83*10 ^-4L, the maximum 20min consuming time of process.

Use computing formula of the present invention:

$C_{\mathrm{VFA}}=\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({\left[H^{+}\right]}_1-K_W/{\left[H^{+}\right]}_1)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0)}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0}$

In the formula: V ₁=V ₀+ V _x

[H ⁺] ₀=10 ^-4.7mol/L

[H ⁺] ₁=10 ^-4.2mol/L

K _w--ion-product constant of-----water, 10 ^-14(25 ℃)

V _X-------adding hydrochloric acid volume (L) is 9.83*10 ^-4

C _Acid--concentration (mol/L) of-----hydrochloric acid is 0.05;

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

The final concentration that gets acetic acid is 4.825mM.

2. same operation process, the sulphion concentration that calculates with the present invention are 1,3, acetate concentration is respectively 4.957mM, 4.975mM, 5.207mM in the artificial synthesis reactor water outlet of 6mM.

As can be known from the results, the maximum relative error by the resulting acetate concentration of the present invention and actual value is 4.14%, and minimum is 0.5%, and this explanation the present invention is not influenced by bicarbonate radical, and method is reliable, the accuracy height.

Embodiment 5:

Under room temperature state, disposing total VFA concentration respectively is artificial each 0.04L of synthesis reactor water outlet of 5mM, and wherein acetic acid and propionic acid ratio are respectively 100%:0,95%:5%, 85%:15%, 80%:20%.

1. in the 300rpm electromagnetic agitation, dripping speed be under the condition of 0.7mL/min, to acetic acid and propionic acid ratio be in the water outlet of 100%:0 dropping concentration be 0.05M hydrochloric acid solution to pH be 4.7, record volume (V at this moment ₀=42.34*10 ^-3L); Continuing with concentration is the hydrochloric acid solution titration of 0.05M, is 4.2 until system pH, and the hydrochloric acid consumption is V _x=1.00*10 ^-3L, the maximum 20min consuming time of process.

Use computing formula of the present invention:

$C_{\mathrm{VFA}}=\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({\left[H^{+}\right]}_1-K_W/{\left[H^{+}\right]}_1)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0)}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0}$

In the formula: V ₁=V ₀+ V _x

[H ⁺] ₀=10 ^-4.7mol/L

[H ⁺] ₁=10 ^-4.2mol/L

K _w--ion-product constant of-----water, 10 ^-14(25 ℃)

V _X-------adding hydrochloric acid volume (L) is 1.00*10 ^-4

C _Acid--concentration (mol/L) of-----hydrochloric acid is 0.05;

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

The final concentration that gets VFA is 4.915mM.

2. same operation process, VFA concentration is respectively 5.053mM, 4.895mM, 4.817mM in the artificial synthesis reactor water outlet that the acetic acid that calculates with the present invention and propionic acid ratio are respectively 95%:5%, 85%:15%, 80%:20%.

As can be known from the results, the maximum relative error by the resulting VFA concentration of the present invention and actual value is 3.66%, and minimum is 1.06%, and this explanation the present invention has good measurability to different VFA in the component, and method is reliable, the accuracy height.

Embodiment 6

Middle moderate temperature UASB reactor to an operation carries out 3 times of concentration of substrate impact loads, and substrate is glucose, and every 1.5h collects a water outlet in the impact process, collects 4 samples altogether.Measure flow process as shown in Figure 1: from anaerobic reactor 1, collect water outlet in the water outlet storage bottle, utilize pump 3 that water outlet is pumped in the magnetic agitation instrument 4, utilize the water outlet in the titrator 6 titration magnetic agitation instrument 4 that connect computer 7, utilize pH electrode 5 to measure the pH of water outlet simultaneously.

Survey VFA concentration with the present invention and gas chromatography, process is as follows: 1. first sample: get the 15ml sample, with distilled water diluting to 30mL, in the 300rpm electromagnetic agitation, dripping speed be under the condition of 0.7mL/min, to wherein drip concentration be 0.05M hydrochloric acid solution to pH be 4.7, record volume (V at this moment ₀=42.56*10 ^-3L); Continuing with concentration is the hydrochloric acid solution titration of 0.05M, is 4.2 until system pH, and the hydrochloric acid consumption is V _x=1.95*10 ^-3L, the maximum 20min consuming time of process.

Use computing formula of the present invention:

$C_{\mathrm{VFA}}=\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({\left[H^{+}\right]}_1-K_W/{\left[H^{+}\right]}_1)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0)}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00003065996400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1/V_0}$

In the formula: V ₁=V ₀+ V _x

[H ⁺] ₀=10 ^-4.7mol/L

[H ⁺] ₁=10 ^-4.2mol/L

K _w--ion-product constant of-----water, 10 ^-14(25 ℃)

V _X-------adding hydrochloric acid volume (L) is 1.95*10 ^-3

C _Acid--concentration (mol/L) of-----hydrochloric acid is 0.05;

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

Final VFA concentration be 24.462Mm, with gas chromatography survey VFA concentration be 26.821mM; 2. same operation process, calculate with the present invention that VFA concentration is respectively 22.336mM, 20.454mM, 18.684mM in second sample, the 3rd sample and the 4th sample, the VFA concentration that records with gas chromatography is respectively 24.284mM, 21.936mM, 19.425mM.

As can be known from the results, the maximum relative error by the measured VFA concentration of the resulting VFA concentration of the present invention and gas chromatography is 8.79%, and minimum is 3.81%, this explanation the present invention vapor-phase chromatography that can match in excellence or beauty, and method is reliable, the accuracy height; Simultaneously, the present invention need not sample is carried out pre-service, compares with vapor-phase chromatography, and is more apparent easy.

The above description of this invention is illustrative, and nonrestrictive, and those skilled in the art is understood, and can carry out many modifications, variation or equivalence to it within spirit that claim limits and scope, but they will fall within the scope of protection of the present invention all.

Claims (4)

1. method of measuring fast volatile fat acid concentration in the anaerobic reactor, it is characterized in that, this method charge balance and whole initial body of solution to be measured when setting up two different pH points is long-pending, release the relation between VFA and the pH, and then calculate the concentration of solution VFA to be measured by acidimetry.

2. the method for claim 1 is characterized in that, the concrete steps of this method are as follows:

(1) under room temperature state, the volume of getting in the anaerobic reactor is V ₀Solution to be measured, and set initial pH value respectively and be respectively pH ₀And pH ₁

(2) be V with volume _xThe described solution to be measured of acid solution titration, be pH until this pH value of solution value to be measured ₁, this moment, the cumulative volume of described solution to be measured was V ₁

(3) the VFA concentration of the described solution to be measured of calculating, computing formula is as follows:

$C_{\mathrm{VFA}}=\frac{({\left[H^{+}\right]}_0-K_W/{\left[H^{+}\right]}_0*f_1\left({\left[H^{+}\right]}_1\right)-f_1\left({\left[H^{+}\right]}_0\right)*({\left[H^{+}\right]}_1-K_W/{\left[H^{+}\right]}_1)*V_1/V_0+f_1\left({\left[H^{+}\right]}_0\right)*C_{\mathrm{acid}}*V_X/V_0)}{f_1\left({\left[H^{+}\right]}_1\right)*f_2\left({\left[H^{+}\right]}_0\right)-f_1\left({\left[H^{+}\right]}_0\right)*f_2\left({\left[H^{+}\right]}_1\right)*V_1/V_0}$

In the formula:

$f_2\left(\right[H^{+}\left]\right)=\frac{K_a}{K_a+\left[H^{+}\right]}$

K _a--the dissociation constant of-----VFA; [H ⁺] ₀=10 ^-pH0Mol/L; [H ⁺] ₁=10 ^-pH1Mol/L;

K _w--the ion-product constant of-----water; V _X--the volume (L) of-----adding acid solution;

C _Acid--the concentration (mol/L) of-----acid solution.

3. method as claimed in claim 2 is characterized in that, described acid solution is hydrochloric acid or sulfuric acid.

4. method as claimed in claim 2 is characterized in that, described pH ₀And pH ₁It is positive and negative 1 that span should select the pk value of VFA to add, described pH ₀And pH ₁Difference greater than 0.2.

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