JPH0114840B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating organic waste liquids such as human waste, which processes the waste liquids in an extremely rational and advanced manner, and removes excess biological sludge generated from the treatment process in an extremely energy-saving manner. The aim is to provide an innovative process that can be processed in a timely manner.

Hereinafter, a description will be given using human waste as an example of a representative waste liquid.

The following process is considered to be the most advanced of all human waste processing processes to date.

That is, after subjecting human waste to biological nitrification and denitrification treatment, the biologically treated water is subjected to coagulation separation (coagulation and sedimentation is common), sand filtration, ozone, and activated carbon treatment.

However, as a result of technical evaluation of this process from a strict viewpoint, the present inventor recognized that the following serious problems were inherent.

Because many unit operations are arranged in series, the process is complicated and maintenance is poor. Also, the installation area becomes larger.

It is only possible to remove phosphorus from the stock solution, but it cannot be recovered as a valuable product.

Phosphorus, SS, COD, and chromaticity cannot be removed to a high degree unless a large amount of inorganic flocculants such as sulfuric acid and ferric chloride are used in the flocculation and separation treatment of biologically treated water. As a result, a large amount of coagulated sludge (mainly composed of Al(OH) ₃ and Fe(OH) ₃ ), which is difficult to dewater, is generated, resulting in a large amount of resources being consumed, and sludge treatment and disposal requires great expense and costs. It takes energy. Additionally, a large amount of fuel such as heavy oil is consumed in drying and incinerating the dehydrated cake. Moreover, when the dehydrated cake is incinerated, the amount of incineration ash generated increases. Furthermore, when composting is performed, there is a large amount of inorganic content, which reduces the quality of the compost product.

Ozone treatment consumes a large amount of ozone generation electricity, and activated carbon treatment also requires a high cost of 500 to 600 yen/Kl/human waste.

The present invention effectively solves all of the above problems, and after biologically treating organic waste liquid such as human waste, the biologically treated water is evaporated and concentrated in an indirect heating evaporation process, and the evaporated water vapor is Using the condensed water as highly treated water of the organic waste liquid, and heating the surplus biological sludge generated from the biological treatment process using the retained heat of the condensed water to dehydrate and/or dry the dehydrated cake. This is a method for treating organic waste liquid, which is characterized by:

An embodiment of the present invention will be described below with reference to the drawings, taking human waste treatment as an example.

The removed human waste 1 (often contaminated with septic layer sludge) is allowed to flow into the biological treatment process 2 using the biological nitrification and denitrification method without adding dilution water, resulting in mainly BOD, NH ₃ - Sufficiently remove nitrogen components such as N. Adding a large amount of dilution water to the biological treatment step 2 not only causes a drop in water temperature but also increases the amount of water to be evaporated, which is extremely undesirable.

Therefore, the activated sludge slurry 3 flowing out from the biological treatment process 2 is transferred to a solid-liquid separation process 4 such as a centrifugal thickener.
Most of the separated sludge separated into solid and liquid is recycled to the biological treatment process 2 as return sludge 5.

Biologically treated water 6 (separated water) from solid-liquid separation step 4
contains large amounts of non-biodegradable COD, chromatic acid, phosphoric acid, and organic nitrogen. For this reason, conventional processes include many unit operations such as coagulation-sedimentation, filtration, ozone treatment, and activated carbon treatment, but the present invention introduces a completely new technical idea.

That is, biologically treated water 6 is preheated in a heat exchanger 7 and then supplied to an evaporator 8, and the evaporated water vapor 9 is compressed and heated in a vapor compressor 10, and then guided to an indirect heating section 11 of the evaporator 8. After reusing the latent heat of condensation of water vapor 9 as a heating source, condensed water 12 is used as highly treated water of human waste 1. Since this highly treated water is distilled water, it exhibits the highest quality water with nearly zero SS, chromaticity, BOD, COD, P, and TN.

Since the condensed water 12 has a high temperature of about 95°C, it flows into the heat exchanger 7 to preheat the feed liquid to the evaporator 8, that is, the biologically treated water 6, and then leads it to the heat exchanger 7', where it undergoes a mechanical dehydration process. 13 (filter press,
It is used to heat surplus biological sludge 14 supplied to a screw press, etc.). The heated excess biological sludge 15 is dehydrated to a water content of 60% or less using a filter press or screw press due to effects such as a reduction in viscosity.

Another method of effectively utilizing the heat retained in the condensed water 12 is to use it as a heating source for the drying process 17 of the dehydrated cake 16 discharged from the mechanical dehydration process 13.

For example, condensed water 12' and air 18 are transferred to heat exchanger 1.
A method of drying the dehydrated cake 16 by introducing heated air (warm air) 20 into the drying step 17 is adopted. The dried material is used as fuel for the boiler incinerator 21, and there is no need to consume heavy oil to incinerate the dehydrated cake as in the conventional case. Steam 22 from the boiler incinerator 21 is used for heating or for the evaporator 8.

In addition to the method of directly using the heat retained in the condensed water 12, the heat released from the refrigerant condensing section of the heat pump 23 is used as a low heat source for the heat pump 23 in the sludge heating process 7' and/or the drying process 17.
The method of supplying the same is also extremely effective.

As described above, the present invention is unique in its technical idea of introducing a new concept to water clarification and effectively utilizing residual heat generated from the water clarification process in the surplus sludge treatment process.

According to the present invention as described above, the following important effects can be obtained.

Since the residual heat from the water treatment process is effectively used,
The processing capacity of the sludge dewatering process is improved, and the dehydrated cake can be dried energy-savingly.

Therefore, not only is no auxiliary fuel such as heavy oil required for incineration of the dehydrated cake, but also the dehydrated cake can be effectively used as fuel. That is, there is an energy creation effect.

Since this is a new process in which organic waste liquid is first subjected to biological treatment and then biologically treated water is treated in an indirect heating evaporation process, there are only two steps, making the process significantly simpler than conventional processes.
Moreover, the treated water exhibits the highest quality water that cannot be achieved with conventional processes.

Water treatment flocculants, ozone, activated carbon, and sterilizers are all eliminated.

Coagulated sludge (Al
(OH) ₃ or Fe(OH) ₃ ) is not generated at all, so the only sludge that needs to be treated is surplus biological sludge, and sludge treatment costs can be significantly reduced.

Since the dehydrated cake does not contain inorganic flocculated sludge that is difficult to dewater, the calorific value of the dehydrated cake is approximately 3800.
It has a high value of ~3900Kcal/Kg-DS and has excellent fuel properties.

The liquid to be evaporated is biologically treated water, and the human waste is not directly evaporated, which causes odor and
There is no scattering of ammonia or volatile organic acids, and there is no clogging of the evaporator due to high concentration SS components in urine and no flow failure caused by liquid concentration.

The concentration of chlorine ions in the water treated with human waste by the conventional process is as high as 300 to 3000 mg/, making it difficult to use as irrigation water for fields and forests due to salt damage, but the chlorine ion concentration of the treated water in the process of the present invention is 0 mg/~. Since it is a trace, it can be sprayed without any problems.

With conventional processes, it was impossible to reduce the SS of treated water to zero, so if the treated water permeated underground, clogging with SS would occur immediately, requiring a vast area of land, making it impractical. However, since the treated water of the present invention is distilled water, it has zero SS and can penetrate underground very easily.

[Brief explanation of drawings]

The drawing is a flow sheet showing one embodiment of the invention. 1... Human waste, 2... Biological treatment process, 3... Activated sludge slurry, 4... Solid-liquid separation process, 5... Returned sludge, 6...
Biologically treated water, 7, 7', 19... Heat exchanger, 8... Evaporator, 9... Steam, 10... Steam compressor, 11... Indirect heating section, 12, 12'... Condensed water, 13... Mechanical dehydration process, 14, 15... Surplus biological sludge, 16... Dehydrated cake, 17... Drying process, 18... Air, 20... Warming air, 21... Boiler incinerator, 22... Steam, 23... Heat pump.

Claims (1)

[Claims] 1. After biologically treating organic waste liquid such as human waste,
The biologically treated water is evaporated and concentrated in an indirect heating evaporation step, and the condensed water of the evaporated water vapor is used as the highly treated water of the organic waste liquid, and the heat retained in the condensed water is generated from the biological treatment step. A method for treating organic waste liquid, which comprises heating surplus biological sludge to dehydrate it and/or drying the dehydrated cake. 2. Claim 1, wherein the condensed water is used as a low heat source for a heat pump, and the heat raised by the heat pump is used as a heat source for heating the excess biological sludge and/or drying the dehydrated cake. the method of.