JPH03207489A - Method for removing phosphorus in liquid - Google Patents

Abstract

PURPOSE:To highly remove phosphorus in a liq. by very simple operation by regulating the electrical conductivity of the liq. to a certain value or above with a soln. of salts and carrying out catalytic dephosphorization. CONSTITUTION:A liq. contg. phosphorus, e.g. waste water from an industrial or living waste water such as sewerage or night soil is introduced into a pretreating stage 2, where a mineral acid is added, air is blown and carbonates is the liq. are removed. Slaked lime and Ca salt are added to regulated the concn. of Ca and the pH of the liq. and a soln. 7 of salts such as NaCl is further added to regulate the electrical conductivity of the liq. flowing in a subsequent dephosphorizing stage 4 to >=2000muV/cm. Suspended solids in the liq. are then removed in a sand filtering stage 3 and the liq. is sent to the stage 4 packed with granules having phosphorus removing ability. By such very simple operation, phosphorus removing performance is considerably enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Industrial Application Field The present invention relates to a method for removing phosphorus contained in domestic wastewater such as sewage and human waste, industrial wastewater, and the like.

[Conventional technology]

When removing phosphorus from a liquid, a phosphorus-containing liquid is treated with granules having phosphorus removal ability in the presence of calcium ions,
For example, the method of contacting with phosphate rock, bone coal, MgO, slag, etc. is a well-known method established as a catalytic dephosphorization method. In this catalytic dephosphorization method, in order to promote the phosphorus removal reaction, it is known that carbonic acid substances that inhibit the phosphorus removal reaction are removed or F ions are added as a promoter.

[Problem to be solved by the invention]

However, secondary treated sewage water (usually 1 to 2 phosphorus)
■ When the catalytic dephosphorization method is applied to water (containing /1), the phosphorus concentration in the treated water is constantly 0.2 to 0.4 even after decarboxylation (removal of carbonated substances in the liquid). If this treated water is reused as landscaping water, algae will grow in the waterways.

Moreover, even if F ions are added, the phosphorus concentration of the treated water can be reduced to 0.2 to 0.4 ■/I! However, if a large amount is added, CaFt will precipitate and the amount of sludge generated will increase.

The object of the present invention is to solve the above-mentioned conventional problems in the catalytic dephosphorization method and to provide a method that can achieve high phosphorus removal performance with extremely simple operations. [Means for Solving the Problem] The present invention provides a catalytic dephosphorization method in which phosphorus is removed by bringing a phosphorus-containing liquid into contact with particulate matter having a phosphorus removal ability in the presence of calcium ions. Add a salt solution to the liquid to increase the electrical conductivity of the liquid to 2,000μIJ/
This method of removing phosphorus in the prefecture is characterized by carrying out contact dephosphorization after adjusting the phosphorus to a level higher than cs.

[Function] To explain the function of the present invention based on drawings showing embodiments, in FIG. Introduce. In pre-treatment step 2, mineral acid is added to the secondary sewage treatment water and air is blown in to remove carbonated substances from the liquid (decarburization #), and then slaked lime and Ca salt are added to carry out the dephosphorization reaction. The Caf74 degree and p}l required for this are adjusted. In this pre-treatment step 2, salt melt Wi. 1 to increase the electrical conductivity of the liquid flowing into the subsequent dephosphorization step 4 to 2,000.
Adjust by more than μ1J/cIn. For example, normal sewage has an electrical conductivity of 500 to 1,500μV/clI, but it can be increased to 2,000μV/CS or more by adding salt solution 7 in proportion to the flow rate, or by using a pretreatment process. An electrical conductivity meter is installed in 2 or in the flow path to the dephosphorization process 4, and is linked to the saline solution injection pump.
It is also preferable to maintain a value of 11/an or more.

As a salt solution that increases electrical conductivity, NaCI gc
l. , BaCl2, CaC]z, or seawater can be used, but seawater is more preferable.

Next, the liquid whose electrical conductivity has been adjusted to 2,000 μv/cm or more is subjected to sand filtration step 3 to remove suspended matter in the liquid.
It is transferred to a dephosphorization step 4 filled with granules having phosphorus removal ability. In the dephosphorization step 4, calcium phosphate is crystallized on granules having phosphorus removal ability, phosphorus in the liquid is removed, and dephosphorized water can be obtained. The dephosphorization step 4 may be of an upward flow type or a downward flow type, and may be a fixed bed or a fluidized bed. As the granular material having phosphorus removal ability, phosphate rock, bone charcoal, light burnt mag inertia converter slag, etc. can be used.

Note that the salt solution 7 may be added not only in the pretreatment step 2 but also anywhere before the dephosphorization step 4, but when seawater is used as the salt solution, it may be added from the sand filtration step 3 as in the illustrated example. If added beforehand, it can also remove turbidity and phosphorus from the seawater, helping to purify the seawater.

Figure 2 is an example of using sand filtration/dephosphorization process 6, which integrates sand filtration process 3 and dephosphorization process 4 in Figure 1, with a sand layer at the bottom and a granular material layer with phosphorus removal ability at the top. The effluent water from the pretreatment step 2 is passed through it.

[Example] Sulfuric acid was added to secondary treated sewage water containing 2 μ/l of phosphorus to adjust it to p}14.5, and seawater was added to adjust the electrical conductivity to various predetermined values. Prepare each of them, and further add CaCI. Solution (20 as Ca
,000*/+! ) to increase Ca to 60-70■
/l, and further added NaOH solution to pH 9.
It was set to 0.

On the other hand, CaCI. A solution was added to adjust Ca to 60 to 70 /1, and seawater was added to adjust the electrical conductivity to various predetermined values.
Furthermore, a NaOH solution was added to each to adjust the pH to 9.0.

Take 1 liter of each of these solutions in a beaker and add 1.0 liters of phosphate rock.
The phosphorus concentration of the supernatant water was measured after 1 hour of reaction after adding 00 μ/l, and the influence of electrical conductivity was examined. The results of these experiments are shown in Figure 3, and the electrical conductivity was 2,000μ.
The phosphorus concentration of the supernatant water decreased significantly when the temperature exceeded p/cs.

In addition, in order to adjust the electrical conductivity, Na
The results using NaC] solution are also shown in Figure 3.
The seawater had better phosphorus removal performance than the l solution.

〔Effect of the invention〕

As described above, in the catalytic dephosphorization method, the present invention provides
Phosphorus removal performance can be significantly improved by an extremely simple operation of adjusting the electrical conductivity in the liquid to be treated to 2,000 μl J/cIl or more by adding a salt solution.

[Brief explanation of drawings]

FIGS. 1 and 2 are system explanatory diagrams showing examples of implementation Li of the present invention, respectively, and FIG. 3 is a diagram showing the relationship between supernatant water phosphorus concentration and electrical conductivity in experimental results. 1...Secondary sewage treatment water, 2...Pre-treatment process, 3...
- Sand filtration process, 4... Dephosphorization process, 5... Dephosphorization treated water, 6... Sand filtration/dephosphorization process, 7... Salt solution.

Claims (1)

[Claims] (1) In the catalytic dephosphorization method, in which phosphorus is removed by contacting a phosphorus-containing liquid with particulate matter having a phosphorus-removing ability in the presence of calcium ions, a salt solution is added to the phosphorus-containing liquid to remove phosphorus. A method for removing phosphorus from a liquid, characterized by carrying out catalytic dephosphorization after adjusting the electrical conductivity to 2,000μ/cm or more.