JPH02261598A - Method for purifying sludge in pond, moat, or the like - Google Patents

Abstract

PURPOSE:To facilitate the separations of water from sludge by returning water discharged in dehydration stage of a sludge to its separation stage after mixing under stirring a solidified material obtained due to separation of water from the sludge by its sedimentation with a flocculent. CONSTITUTION:Sludge concentrated in a primary tank 41 is fed into a secondary tank 42 and flocculated by adding a flocculent 10 to form a hydratable cake. Removed water obtd. in a dehydrating stage 12 is fed into the primary tank 41. A flocculent contained in the water at a relatively low concn. bonds to sludge to further lower the concn. and the flocculation and sedimentation of the sludge are facilitated by the action of the flocculent.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention can effectively purify sludge deposited on the bottom of a pond, moat, or relatively small river where a predetermined amount of water is stored. This relates to a sludge purification method that allows the water to be returned again.

[Conventional technology]

The required amount of water is always stored in lakes, rivers, ponds, castle moats, and other moats and reservoirs. In addition to rainwater, other impurities such as sewage, fallen leaves, and dirt flow into these moats and ponds.The secondary inflow impurities accumulate or rot on the pond and moat bottoms, becoming sludge, which forms sludge in the ponds and moats. It pollutes the quality of stored water.

Methods for removing this sludge include pumping and draining water from ponds and moats, drying the pond, and mechanically or physically removing the sludge that has settled and accumulated at the bottom; There is a dredging method in which water is pumped up together with sludge using a sand pump or the like, a flocculant is mixed into the pumped water to separate it, solids are removed, and the supernatant water is returned to a pond, moat, etc.

(Problem to be solved by the invention) In the method of drying a pond, etc. and mechanically removing the settled and accumulated sludge, - Drain the water from the pond or moat, that is, completely drain it, and expose it to sunlight etc. After drying to some extent, it is discharged using a bulldozer, etc., which takes time and effort to drain ponds, etc.
Additionally, during sludge removal work, the function of ponds and moats will be temporarily suspended, and the landscape will be spoiled.

In the dredging method, a flocculant is added to pumped-up sludge water and stirred to remove solid matter from the sludge. The pre-flocculant still remains in the waste water from which the sludge solids have been dehydrated.

The TLs (half survival limit concentration) indicating acute fish toxicity of cationic polymers is 0.2 to spp-.

Since there is a cationic polymer of about 11-1 Opp in dehydrated wastewater, if this dehydrated wastewater is returned to its original pond or moat, it will kill aquatic animals such as fish due to the toxicity of this coagulant. becomes.

After mixing with a neutralizing agent suitable for this drainage house and neutralizing it, the water is returned to the pond, etc. Therefore, there is a drawback that the amount of flocculant used increases depending on the amount of sludge treated, and the amount of neutralizing agent used also increases.

The object of the present invention is to suppress the amount of neutralizing agent used as much as possible and to perform desired sludge purification.

[Means to solve the problem]

Water from ponds, moats, etc. is pumped up together with the sludge that has settled and accumulated at the bottom, and this is separated by sedimentation, and the supernatant water is returned to the pond, moat, etc., and a flocculant is mixed and stirred into the solid substances that have settled and separated. After coagulation, this is dehydrated in a dehydration process and discharged as sludge, and the waste water from this dehydration process is returned to the sedimentation separation process.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sludge purification method of the present invention will be explained below based on embodiments shown in the drawings.

A pump 2 pumps up water from a moat or pond 1 such as a lake, river, pond, castle moat, or reservoir together with the sludge that has settled and accumulated at the bottom. This pumped water such as sludge is led to a coagulation concentration tank 4 through a pumping pipe 3 to separate the sludge solid content and supernatant water in this pumped water. In this case, the pump 2 used is as shown in Fig. 1. This pump 2 is installed above the oil.
The dredging pipe 5 connected to the dredging pipe 5 is supported by a float 6 or the like to follow changes in the water level, and when the tip of the dredging pipe 5 reaches a predetermined depth, it is possible to dredge the sludge that has settled and accumulated at the bottom. As shown in Figure 2, a dredging pump is placed into the water in the pond or moat to directly suck up the sludge. Other methods are also possible.

Although there may be only one coagulation concentration tank 4, as shown in the figure, a primary tank 41 and a secondary tank 42 are used, and the sludge water pumped and discharged in the secondary tank 41 is sedimented and separated. The purpose of the sedimentation and separation of this sludge is to naturally separate and settle by utilizing the difference in weight, but this secondary tank 41 is supplied with desorbed water obtained in the dehydration process described later, along with sludge water from the pumped water. . By doing so, the relatively low concentration flocculant contained during this desorption combines with the sludge, resulting in an even lower concentration, and on the other hand, the action of the flocculant promotes coagulation and sedimentation of the sludge.

The supernatant water from which the sludge solid content has been separated in the secondary tank 41 is returned to the pond or moat via the return pipe 7. At this time, the low concentration flocculant component contained in the desorption obtained in the dehydration process combines with the sludge component of the sludge water newly supplied into this next tank, and the degree of sludge content further decreases. and rendered harmless.

The sludge concentrated in the primary tank 41 is supplied to the secondary tank 42 via the pump 8 and the supply pipe 9. A flocculant 10, such as a cationic polymer, is put into the secondary tank 42 in accordance with the amount of sludge and mixed and stirred to coagulate the sludge into a solid form that can be dehydrated. The addition of the cation bomber and mixing and agitation can also be carried out by a line mixer or other means.Then, the cation bomber is transferred from the secondary tank 42 via the pipe 11 to the dehydration step 12. In this dehydration step 12, the sludge solid content containing a large amount of water is dehydrated to the extent that it can be dumped or landfilled, and the sludge content becomes a solid body whose moisture content is reliably reduced to the required moisture content. The dewatering equipment used in this dewatering process includes a fixed or mobile belt press type dehydrator disclosed in Japanese Patent Publications No. 60-89 and No. 62-54048, for which the applicant has already obtained a patent, and a pressurized type dehydrator. It is possible to employ a dehydrator, a centrifugal separator, etc., and this model is not limited.

The sludge solid content dehydrated in this dehydration process is carried out by truck or conveyor and dumped or landfilled, but the desorbed water obtained by this dehydration is once received in the filtrate receiving tank 13.
This is passed through the pump 14 and the return water pipe 15 to the primary tank 41.
supply to The cationic polymer in the desorbed water combines with the sludge water supplied into the primary tank and contributes to the coagulation of the sludge, thereby further reducing the concentration of the cationic polymer in the desorbed water.

Figure 3 shows the mass balance when 5 tons/hour of dredged sludge was purified based on the above example. In Figure 0, the cationic polymer was added in an average of 0.15% to the solid matter. An average of 1 to 3 ppm of residual cationic polymer was detected in the desorbed water.

Although the water content of the settled sludge actually fluctuated between 78% and 85%, the amount of flocculant added was kept constant, so the cationic polymer concentration in the desorbed water was at a maximum of 20ppm+.
However, it was not detected in the supernatant water after mixing with the sludge.

In addition, in the embodiment shown in Fig. 1, all of the desorbed water obtained in the dehydration process is returned to the secondary tank 41, but the concentration and amount of this desorbed water is greater than the allowable amount to be returned to the primary tank or the allowable value. In this case, even if the contained flocculant components are used to flocculate newly supplied sludge water in the next tank, the unreacted flocculant components are mixed into the supernatant water and returned to the pond, etc. There is a risk of water being discharged into the pond. In order to prevent this, in the embodiment shown in FIG. 2, a sensor 16 is installed in a part of the return water pipe 15 to detect the concentration of flocculant remaining in the returned water and the amount of returned water. Return water pipe 1 via adjusting neutralizing agent supply control mechanism 17
The pulp 18 disposed in the tank 5 is controlled to adjust the amount returned to the next tank. This valve 18 also has a neutralization tank 19.
A return water pipe 20 is installed, and the desorbed water from the r-liquid receiving tank is not supplied to the primary tank, but is supplied to the neutralization tank 19, where an appropriate amount of a neutralizing agent 21, for example, an anionic polymer is added and neutralized. After that, the fish should be returned to the pond, etc.

Furthermore, a system for attaching the neutralizing agent 21 is also installed in the overflow tank 22 installed adjacent to the secondary tank 41, so that if #collecting agent components remain in the supernatant water, neutralization can be performed as an emergency measure. Do it like this.

〔Effect of the invention〕

According to the present invention, the desorbed water obtained in the dehydration process is transferred from the pond to @1! Since it is mixed with wastewater containing drained sludge, the low concentration flocculant components remaining in the desorbed water undergo a coagulation reaction with the sludge water in the primary tank and become harmless, and the sludge water settles. Separation is facilitated.

According to the second aspect of the invention, the amount of desorbed water obtained in the dehydration step and the concentration of the remaining flocculant component are detected, and the desorbed water supplied to the next tank is combined with sludge water and the amount that can be removed is Since the water returned to the pond exceeds this limit, a neutralizing agent is added to it, making it even more certain that the water returned to the pond is harmless and will not have any impact on aquatic animals. Moreover, continuous treatment is possible regardless of the amount of Fi water syneresis, the concentration of the flocculant, etc.

[Brief explanation of drawings]

l is a pond or a moat; 2. 8. 14 is a pump, 4 is a coagulation concentration tank, 41 is a primary tank, 42 is a secondary tank, 7 is a return pipe, 9 is a supply pipe, 10 is a flocculant, 12 is a dewatering process, 15 is a return water pipe, 16 is a sensor 21 is a neutralizing agent.

Claims (2)

[Claims] (1) Water from a pond, moat, etc. is pumped up together with the sludge that has settled and accumulated at the bottom, and this is separated by sedimentation, and the supernatant water is returned to the pond, moat, etc., and a flocculant is applied to the solid substances that have settled and separated. A method for purifying sludge in ponds, moats, etc., characterized by mixing and agitating and flocculating it, dewatering it in a dehydration process and discharging it as sludge, and returning the wastewater from this dehydration process to a sedimentation separation process. . (2) Detect the coagulation residue concentration and amount of wastewater input in the previous process of the wastewater obtained in the dewatering process, appropriately control the amount returned to the sedimentation separation process, and adjust the surplus wastewater from the dewatering process to an appropriate amount. 2. The method for purifying sludge in ponds, moats, etc. according to claim 1, wherein after neutralizing by adding a neutralizing agent, the sludge is returned to the pond or moat.