JPS5841916B2 - How to dispose of waste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for treating waste containing organic carbon and ammonia nitrogen.

One method for treating waste containing organic carbon is to digest it by anaerobic fermentation to generate methane gas, and then compost the remainder.

This is an advantageous processing method, as fuel gas and fertilizer can be obtained with little energy consumption.

However, even if the waste contains organic carbon, the efficiency of anaerobic fermentation is low for waste that contains large amounts of ammonia nitrogen, such as barber or livestock excrement, and it takes a long time to generate methane gas. , and the final amount generated is also small.

Advances in research have revealed that anaerobic fermentation has an appropriate quantitative relationship between organic carbon and ammonia nitrogen in the processed material.

The ratio is approximately C:N=10-20:1 in atomic ratio.
It is considered to be within the range of

Therefore, attempts were made to add a carbon source to maintain balance so that the C:N ratio would be within the above-mentioned preferred range.

However, even if this measure improves the efficiency of fermentation, problems still remain.

This is because if the digested product after fermentation is separated into solid and liquid, the solid substance can be used as an organic fertilizer, but the liquid substance has low concentration of fertilizer components and contains a large amount of salt, so it has no utility value. Not worth it.

However, since it also contains a large amount of ammonia nitrogen, it is not preferable to release it as is.

The present inventor has completed research with the intention of solving such problems and making waste treatment by anaerobic fermentation industrially viable.

Therefore, an object of the present invention is to improve the gas generation efficiency when treating organic waste containing a large amount of ammonia nitrogen by anaerobic fermentation, and to reduce the amount of ammonia nitrogen contained in the liquid after fermentation. The object of the present invention is to provide a processing power method that facilitates treatment for discharge.

The waste processing power method of the present invention, when processing waste containing organic carbon and a large amount of ammonia nitrogen,
By adding alkali to the waste and applying it to a stripping device, part of the ammonia nitrogen is removed by dissipating as ammonia gas, thereby adjusting the carbon to nitrogen ratio in the waste to a range suitable for anaerobic fermentation that generates methane gas. death,
It is characterized in that it is then subjected to anaerobic fermentation.

In a preferred embodiment, the ammonia gas generated from the ammonia nitrogen described above is absorbed with sulfuric acid or a mixed solution of sulfuric acid and phosphoric acid, and other fertilizer components are blended with this as necessary to recover it as a liquid fertilizer. .

In other words, the present invention differs from the conventional method in that it sets the ratio of carbon and nitrogen in the material to a value appropriate for anaerobic fermentation by expelling ammonia nitrogen, and
It is based on the idea of making it easier to treat the liquid after fermentation, and recovering and effectively utilizing the ammonia nitrogen that has been driven out.

The processing method of the present invention will be explained with reference to the drawings.

First, the waste WM to be treated is stored in the storage tank 1, and an alkali is added thereto from the alkali agent tank 11 to adjust the pH to 10 or more, preferably 11 to 12.

The alkali may be slaked lime powder or slurry, but of course it may also be hydric soda.

The alkaline waste is fed by a pump 12 to the top of the stripping tower 2, where it falls down to strip and drive out ammonia nitrogen in the form of ammonia gas.

The ammonia-containing gas is sent to the absorption tower 3, where it is absorbed and fixed by sulfuric acid or a mixture of sulfuric acid and phosphoric acid falling from the top while going from the bottom to the upper blade.

The gas from which ammonia has been removed in the absorption tower 3 is returned to the bottom of the stripping tower 2 by a blower 21 and used as an air source for stripping.

The waste after ammonia stripping that comes out from the bottom of the stripping tower 2 is received in the pH adjustment tank 4, where it is neutralized by adding acid such as sulfuric acid from the acid tank 41, and the pH is returned to about 7 to 8. Send to anaerobic fermenter 5.

As mentioned above, ammonia stripping is C:N
=10 to 20:1.

Fermentation may be carried out by either medium-temperature fermentation carried out at a temperature of around 35°C or high-temperature fermentation carried out at around 55°C.

This fermentation operation may be carried out as known in the commercial art.

As a result, a gas G whose main component is methane is obtained, which can be used as a fuel or the like.

The liquid material digested by fermentation is sent to an aeration adjustment tank 6 where it is aerated using air or oxygen, and then separated into solid and liquid components by a solid-liquid separator 7.

The former is used as compost Cmp, the latter is treated in another bulk tank 8 and sedimentation tank 9, and the upper water to be treated TW is discharged.

A part of the absorption liquid circulated by the pump 32 to the above-mentioned absorption tower 3 is diverted from the storage tank 31 to the component adjustment tank 33, and from the adjustment component storage tank 34, a desired component to be added such as a potash component is mixed. Use as liquid fertilizer LF.

Various embodiments are possible for the present invention. For example, since stripping of ammonia gas is more efficient at higher temperatures, heating by burning a part of the methane gas produced by fermentation is particularly recommended. Preferable in winter and in cold regions.

Considering the need for heating during fermentation, it is more advantageous to perform ammonia stripping with heating before fermentation rather than after.

Also, in this connection, a combination of high temperature stripping and high temperature fermentation can be considered.

The use of zeolites as filter aids in solid-liquid separators is known per se, as ammonia nitrogen is adsorbed and, in addition to reducing the nitrogen content in the effluent,
This is advantageous because it provides an opening for increasing the strength of the fertilizer components in the compost.

Example When we analyzed the sewage of pig manure and urine discharged from a certain farm, the following results were obtained.

BOD 11,000p West Total Solids
69,000 // Volatile solids 48,000 // Kjeldahl N 4.200 // Ammoniacal N 3. ], 00 ttC:N
4.5 In this pig farm, about 70% of the waste is removed, that is, the feces in the excrement is first removed and composted, so the waste is mainly urine, with little feces, and therefore the waste material is mostly urine. This is because the proportion of ammoniacal N in nitrogen (total nitrogen) is high.

Slaked lime was added to this wastewater to adjust the pH to 12, air was blown in to strip the ammonia, and then neutralized with sulfuric acid to adjust the pH to 7.B.

After this treatment, the residual amount of ammoniacal N was measured and was found to be 1.200.

c: The value of N had increased to 11.1.

Digested sludge obtained from another anaerobic fermenter of pig manure was allowed to stand until no gas was generated, and then used as seed sludge, and mixed in a 1:1 ratio with the sewage from which a portion of the ammonia nitrogen had been removed. The mixture was mixed and subjected to anaerobic fermentation in a constant temperature bath at 35° C., and the amount of gas generated was examined day by day.

For comparison, the amount of gas generated was tracked under similar conditions for wastewater I in which ammonia nitrogen was not removed.

The results are as shown in FIG. 2, and the case according to the present invention (curve I) shows that gas generation is faster than in the comparative example (curve ■), and the total gas generation that can be achieved is amount,
In other words, the digestibility is also high.

(Note that the amount of gas generated is the value per kg of input organic material.

) The air containing ammonia gas expelled by the above-mentioned stripping operation is 20% H2SO4 and 10% HsP.
It was passed through a 1:1 mixture of O4 to absorb the ammonia therein.

When the pH of the solution became neutral, analysis of nitrogen and phosphorus revealed that N:P2O5=4.5:3.5.

KCI was blended with this to obtain a liquid fertilizer containing the three elements of fertilizer.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for explaining a typical aspect of the waste/material processing method of the present invention. FIG. 2 is a graph showing the cumulative amount of gas containing methane as a main component generated by anaerobic fermentation in an example of the throughput method of the present invention, together with a comparative example.

Claims (1)

[Claims] 1. When treating waste containing organic carbon and a large amount of ammonia nitrogen, a portion of the ammonia nitrogen is converted into ammonia gas by adding alkali to the waste and applying it to a stripping device. A method for treating waste, which comprises adjusting the ratio of carbon and nitrogen in waste to a range suitable for anaerobic fermentation that generates methane gas by dissipating and removing the waste, and then performing anaerobic fermentation. 2. The processing power method according to claim 1, in which slaked lime or aqueous soda is used as the alkali added to the waste, and the waste is made alkaline to a pH of 10 or higher and then applied to a stripping device. 3 The ratio of carbon to nitrogen in the waste is C:N = 10 to 20.
The processing method according to claim 1, wherein anaerobic fermentation is carried out by adjusting the atomic ratio to a range of 1:1 (atomic ratio). 4. The processing power method according to claim 1, wherein after ammonia gas is diffused and removed, acid is added prior to anaerobic fermentation to lower the pH to around 7 to 8. 5. The processing power method according to claim 1, in which anaerobic fermentation is carried out at a temperature around 35°C. 6. The processing power method according to claim 1, in which anaerobic fermentation is carried out at a temperature around 55°C. 7 The ammonia gas diffused and removed in the ST-IJ topping device is absorbed with sulfuric acid, and if necessary, other fertilizer components are blended with this to make a liquid fertilizer.Claim 1
How to process terms. 8. Ammonia gas diffused and removed in a stripping device is absorbed with a mixed solution of sulfuric acid and phosphoric acid, and other fertilizer components are blended with this as necessary to make a liquid fertilizer. Processing power method.