JPS62117699A - Electrolytic dehydrating method for sewage sludge, night soil sludge or the like - Google Patents

Abstract

PURPOSE:To permit chemical-less dehydration of sludge and to make filtration power higher than the filtration power of the conventional method by using an iron material for an anode and a stainless steel material for a cathode to make treatment and subjecting the treated sludge to the filtration and dehydration after such treatment in the stage of subjecting sewage or night soil sludge, etc., to an electrolytic treatment. CONSTITUTION:The hardly filterable sludge contg. a large amt. of org. material generated in sewage and night soil treatment plants is electrolytically treated and is then subjected to the dehydration treatment. The iron material is used for the cathode and the stainless steel material for the anode as the electrode materials for making the above-mentioned electrolytic treatment and after the sludge is electrolytically treated for 60-120min, the slude is subjected to the filtration and dehydration. As a result, the use of ferric chloride and slacked lime is not required and the electrode consumption and chemical cost are made lower than in the conventional electrolytic dehydration method without the need for the addition of the antioxidant for the electrodes and without the need for a mechanical cleaning operation for the electrodes. The installation for adjusting the sludge is simple and the electrolytic dehydration method of the easy operation is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention is applicable to
This relates to an electrolytic p-superdehydration method for difficult-to-filter sludge containing a large amount of organic matter such as digested sludge, surplus sludge, mixed raw sludge, etc.
In particular, this invention improves the electrolytic treatment method used as a sludge preparation method before filtration and dewatering, and enables chemical-free dewatering of sludge, which was previously considered to be extremely difficult. Compared to the conventional method, the filtration capacity is greatly improved, and
The aim is to provide an economically inexpensive method.

``Prior art'' Dewatering of highly viscous sewage and human waste sludge, which contain highly hydrophilic organic or inorganic fine particles and colloidal particles, and which have dissolved and clouded multivalued organic substances. In this case, the filtration resistance of the cake formed on the P material is large and blocks the passage of the P solution, resulting in very low efficiency filtration. Therefore, it was considered impossible to perform filtration and dehydration using pressure dehydrators, vacuum dehydrators, belt presses, centrifuges, etc.

In order to solve these problems with temporary dewatering of sludge, the current method of preparing sludge before filtration and dewatering is to add non-containing substances such as ferric chloride, iron sulfate, and aluminum chloride to the sludge. Using flocculants, organic polymer flocculants such as polyacrylamide threads, various amines, formaldehyde condensate threads, etc., and adding and mixing filter aid A such as slaked lime and diatomaceous earth, dewatering of sludge can be carried out. Most of the methods use the Rakuchu dehydration method, which facilitates temporary dehydration.

In addition, instead of performing chemical injection dehydration, iron material is used as an anode and aluminum material is used as a cathode, or vice versa, aluminum material is used as an anode. There is a method of electrolysis treatment using iron material as the three electrodes, followed by temporary dehydration without chemical injection, but when aluminum material is used as the electrode material, an oxide film is formed on the surface of the ``6L electrode, resulting in poor conductivity. ``Problems to be solved by the invention'' include drawbacks such as a decrease in electrolysis efficiency, a large amount of aluminum consumption, and high running costs.As mentioned above, inorganic or organic flocculants and Because of these additives, the pouring dehydration method using v5 superaid,
- After excessive dehydration, various problems arise in both solid and liquid K. In other words, the inorganic flocculant is acidic,
Because slaked lime is alkaline, nonflammable, and dusts, the volume of dehydrated cake increases, making it necessary to use dehydrated p-liquid and cake leachate, and when disposing of it by incineration, the amount of heat retained by the cake decreases. However, there are problems such as increased amount of fuel, increased amount of incineration residue, and generation of harmful substances. Furthermore, although organic polymer flocculants are considered to be harmless, their accumulation and decomposition in the natural environment over many years remains unresolved, and they are contained in both the dehydrated P solution and the cake. There are problems such as being discharged.

Even in these electrolytic dehydration methods that do not use drugs, ``ft.
When aluminum is used as an electrode material for either the negative or anode, first of all, when aluminum is used as the anode material, a large amount of aluminum is extracted, and its consumption costs are high. In addition to being expensive, an oxide film is formed on the electrode surface, which inhibits electrical conductivity and reduces electrolytic efficiency. Alternatively, electrolysis will not continue unless it is mechanically removed using ultrasound or the like.

In addition, when aluminum is used as the cathode material, the cathode generally does not elute, but when the cathode is aluminum, since aluminum is an amphoteric metal, OH- generated by electrolysis of water near the cathode Reacts and chemically dissolves to produce amic acid, resulting in cathode depletion. When aluminum is used as a cathode material, the consumption amount is smaller than when it is used as an anode material. From an economic standpoint, this is a non-negligible cost, and as a cathode material, it would be better if it did not wear out.

"Means for solving the problem" Therefore, in order to solve the problem, the inventors developed a method completely different from the conventional chemical injection dewatering method, that is, after electrolytically treating the sludge, various dewatering methods were used. As mentioned above, using the electrolytic dehydration method, which temporarily dehydrates sewage sludge in a machine, the dehydration capacity is improved compared to the conventional chemical injection method and electrolysis method, and it is also economical. They succeeded in developing an electrolytic dehydration method that was inexpensive and easy to use and operate.

The gist of this is that, as a treatment before temporary dehydration of sewage or human waste sludge, etc., a direct current is applied in a decomposition tank using iron as the anode material and stainless steel as the negative material. By electrolytically treating the sludge for 60 to 120 minutes, the transient nature of the sludge is improved, and the sludge can be efficiently dehydrated using a pressure dehydrator or a vacuum dehydrator without using agents such as flocculants or filter aids. It is designed to allow excessive dehydration.

Conventionally, electrolysis in this field has been used as a water treatment method for wastewater, such as wastewater purification and electrolytic flotation concentration. There are countless examples of the E method being used.

To explain this in more detail, iron ions are eluted from the iron material used as the anode material by an electrolytic reaction, and the eluted iron ions react with water to produce iron hydroxide. This iron hydroxide causes the sludge to coagulate, producing sludge flocs. The generated floc undergoes various electrolytic reactions such as oxidation, reduction, decomposition, and precipitation continuously and repeatedly by direct current flowing between the two electrodes, and is reformed into a hydrophobic floc that is easily dehydrated. This allows for chemical-free filtration and dehydration of sludge.

As for the electrical treatment conditions, for electrolytic dehydration of sewage and human waste sludge, etc., it is appropriate to use iron as the positive electrode material and stainless steel as the cathode material. The sludge in the treatment tank is mixed with agitation at the bottom and circulation in which it is extracted from the bottom and showered over the entire surface of the electrolytic tank from the top, giving sufficient diffusion and flow rate to the sludge in the electrolytic tank, and reducing the amount of sludge remaining at the top of the electrolytic tank. According to experimental results, suppressing the formation of scum containing accumulated air bubbles is required as a way to increase the efficiency of sludge electrolysis. In addition, it is advantageous for the processing voltage to be as low as possible in terms of equipment and safety, but in reality, a range of 3 to 20 V is easy to handle, and the energization DC value is determined by the type of sludge. , differs depending on the ingredients and the desired treatment effect, but 0.
3 to 5 (71), and the electrolytic treatment time is approximately 60 to 120 minutes.

However, if the electrolytic treatment of mud is continued,
Oxidation, contamination, adhesion of impurities, etc. on the electrodes impede the conduction, and unless the voltage is gradually increased, the desired current value cannot be obtained, which results in an increase in squid. becomes.

Conventional methods for preventing these problems include adding a small amount of salt, calcium fluoride alone or a combination of both, and replacing the anode and cathode from time to time in order to reduce the trace power. etc., but these methods are
In both cases, the installation becomes complicated and the cost of electrolytic treatment increases.

Therefore, we provide a small amount of ffl (1 of sludge condition) at a timely time (14 times per 10 to 40 hours), 500 to 1 /
By combining hydrochloric acid (2000) with 'ffs and electrolytically treating it, the activity of the electrode surface can be restored, and other operations such as addition of salt, psium fluoride, or polar conversion can be carried out. They discovered that it is possible to continue electrolysis without doing so.

In addition, Umeyama chose stainless steel as the positive electrode material, iron as the cathode material, and the iron floc produced by elution from the iron material of the anode has superior dehydration properties compared to other aluminum flocs. In addition, the stainless steel material for the cathode does not react with the OH- produced by the 1f solution of water and is not consumed. This is because it has an i-like property and at the same time has almost no sludge adhesion.

To explain this with reference to the diagram, sewage or human waste sewage or human waste is stored in the waste treatment tank 1 as shown in the flow sheet of Figure 1.
After adding a very small amount of hydrochloric acid to this sludge at the appropriate time, stirring and driving the shower circulation pump 2, the sludge was heated to 3~20V, 0.3~5A using the DC power supply 3.
After electrolytic treatment for 60 to 120 minutes at a voltage of about /ff, the treated sludge is removed from the electrolysis tank and supplied to a pressure dewatering machine 5 using a %ζ/p4 or the like, where it is subjected to hyper-flushing. .

Although it is economical to change the operating conditions as appropriate depending on the type and concentration of sludge to be treated, this method requires that the current flowing through the TF8J sludge be changed appropriately or the treatment time may be slightly increased or decreased. The desired treatment effect can be fully achieved by using this method, and it is also easier to install the operation pipe than other methods.

As is clear from the above description, the present invention uses iron material as an anode and stainless steel material as a cathode to treat sewage sludge, human waste, etc., while adding hydrochloric acid at appropriate times and using sufficient stirring and circulation. By electrolytic treatment, the filtration efficiency is higher than the electrolytic treatment method using γp-lumi as either the negative or positive electrode material, without using conventional flocculants or filter aids. The biggest advantage is that the equipment is simple and economical, and the electrolytic one-state water method is the most important feature.

``Example'' The results of electrolytic treatment of sewage sludge and IF2 over-dehydration of the treated liquid using the intermittent >1 solution treatment equipped with the stirring and removing α-ray device as shown in Figure 1 are as follows. Shown below.

Raw solution used in the experiment: Mixed sewage raw sludge (1)
Conventional drug dosing method: 10% ferric chloride (vs. DS, 40% slaked lime (vs. DSS comb added IJ!).

(2) The above stock solution 200e was placed in an electrolytic bath using an iron material as an anode material and a stainless steel material as a cathode material, and the electrode surface was not activated with hydrochloric acid, and the DC voltage was 4°8V and the current was 40.
Electrolytically treated at 0A for 90 minutes (3) Above raw materials +M
2O0e has already been electrolyzed by adding hydrochloric acid, and is placed in an electrolytic cell with an iron material whose surface has been activated as an anode and a stainless steel material as an electrode, and a DC voltage of 4, OV, ? treated with a flow of 400A for 90 minutes.

The above three types of treated solutions were subjected to a p-excess dehydration test using a pressurized dehydrator with a p-excess area of 1.64, and the results of comparing the dehydration operability and the properties of the produced cake are shown below.

(4) Next, apply 200 g of concentrated hydrochloric acid to 200 g of raw sludge at the appropriate time.
The graph in FIG. 2 shows the transition rate when electrolytic dehydration is continued with the addition of 0 mJ.

The addition of hydrochloric acid gave a clear improvement in p-speed.

"Effects of the Invention" As detailed above and shown on the bottom side, according to the present invention, there is no need to use conventionally used ferric tetraoxide or slaked lime, and the electrode There is no need for the addition of antioxidants or mechanical purification operations, the electricity consumption costs and chemical costs are low, the sludge conditioning equipment is simple, and the electrolytic dehydration method is easy to operate. It becomes possible.

[Brief explanation of drawings]

Fig. 1 is a flow sheet of the electrolytic dehydration method for sewage sludge, raw sludge, etc. according to the present invention, and Fig. 2 is a graph showing the off-shore velocity change of sludge treated by the method according to the invention. . 2nd Figure 10-: 5 mud 200/hfjL3”kaL200 m
l ki-! f>j)D r W.

Claims (3)

[Claims] (1) After electrolytically treating difficult-to-filter sludge containing a large amount of organic matter generated in sewage and human waste treatment plants, iron material is used as the electrode material for the electrolytic treatment when dehydrating it.
An electrolytic dehydration method for sewage sludge, human waste sludge, etc., which is characterized by using a stainless steel material for the cathode and then dehydrating it. (2) A method for electrolytic dewatering of sewage sludge, human waste sludge, etc. as set forth in claim (1), characterized in that the sludge to be electrolyzed is stirred or circulated and flowed and diffused. (3) The electrolytic dehydration method for sewage sludge, human waste sludge, etc. as set forth in claim (1), characterized in that a very small amount of hydrochloric acid is added to the sludge to be electrolyzed.