Method And Apparatus For Removing Iron From Humus-Rich Water

Abstract

The invention relates to a method and apparatus for treating water. Iron is removed biologically from humus-rich water with the solution according to the invention. In the method, the water being treated is conveyed through a filter, which filter comprises filter material. Before the water is conveyed to the filter, the pH value of the water is lowered with an acidification part that is included in the apparatus.

Claims

1. A method for treating water, with which method iron is removed from humus-rich water biologically, and in which method the water being treated is conveyed through a filter, which filter comprises filter material, wherein before conveying the water through the filter, the pH value of the water is lowered so that the pH value of the water that has been filtered through the filter is about 3.1-6.0, and iron is removed from the water as it precipitates when iron bacteria oxidize it biologically and the precipitated iron takes humus with it and both the iron and humus adhere to the filter material.

2. The method according to claim 1, wherein the humus is removed from the water by binding it to oxidized iron.

3. The method according to claim 1, wherein the pH value of the water being treated is lowered by adding acid to the water.

4. The method according to claim 3, wherein the pH value of the water being treated is lowered by adding sulphuric acid or hydrochloric acid to the water.

5. The method according to claim 1, wherein the water being treated is aerated before conveying the water to the filter.

6. The method according to claim 1, wherein the quality characteristics of the water being treated are measured to determine the amount of acid to be added to the water that is required for iron removal.

7. The method according to claim 6, wherein the required amount of acid to be added to the water is calculated based on the measurement results of the quality characteristics of the water before the iron removal process is put into operation.

8. The method according to claim 1, wherein a process design is made for the iron removal process before the iron removal process is put into operation, in which process design at least one or more of the following quality characteristics are measured: iron content, oxygen content, pH value, alkalinity, carbon dioxide content, TOC.

9. The method according to claim 1, wherein the pH value of the filtrated water is measured and the amount of acid to be added to the water being treated is adjusted by feedback based on the measurement data.

10. The method according to claim 1, wherein the water being treated is filtrated through a rinseable filter.

11. The method according to claim 1, wherein iron is removed from the water being treated biologically with bacteria, such as iron bacteria.

12. The method according to claim 1, wherein the amount of acid to be added to the water being treated is kept such that the pH value of the water that has been filtered through the filter (4) is about 3.1-6.0.

13. The method according to claim 12, wherein the amount of acid to be added to the water being treated is kept such that the pH value of the water that has been filtered through the filter is about 4.1-4.5

Description

LIST OF FIGURES

[0073] In the following, the invention will be described in detail by the aid of examples by referring to the attached simplified and diagrammatic drawings, wherein

[0074] FIG. 1 presents simplified and diagrammatically a water purifying apparatus employed in the method according to the invention,

[0075] FIG. 2 presents simplified and diagrammatically the apparatus according to FIG. 1 and, attached to it, a biofiltration or limestone filtration apparatus according to prior art, and

[0076] FIG. 3 presents simplified and diagrammatically a method according to the invention for removing iron from humus-rich groundwater.

DETAILED DESCRIPTION OF THE INVENTION

[0077] FIG. 1 presents an advantageous apparatus 10 according to the invention for removing iron and humus biologically from groundwater. Advantageously, the apparatus comprises an inlet 1 for the water to be treated, through which the water to be treated is fed into the apparatus 10. The inlet 1 may be connected to, for example, a delivery pipe or piping. After the inlet 1, in the direction of motion of the water, the apparatus 10 comprises an acidification part 2, which is in contact with the water being treated and with which acid is added to the water being treated to lower the pH and/or alkalinity of the water. After the acidification part 2, in the direction of motion of the water, the apparatus 10 further comprises an aeration part 3, which comprises measuring and adjusting equipment for measuring the oxygen content of the water and for adjusting it to a desired level. The main purpose of the aeration part 3 is to add oxygen to the water being treated.

[0078] In the direction of motion of the water being treated, the apparatus 10 further comprises a filter 4, to which the water is arranged to be conducted after the aeration part 3. The filter 4 comprises filter material 4a that is advantageously sand, for example. It is not required to automatically adjust the amount of air of the water that is conducted to the filter 4. The apparatus 10 comprises, however, at least one oxygen meter for measuring the oxygen content of the filtrated water exiting the filter 4 and for monitoring the efficiency of the aeration. The oxygen content is not, however, critical provided that the oxygen content is sufficiently high. Advantageously, the oxygen content is defined case-specifically.

[0079] The apparatus 10 according to the invention further comprises an outlet 1a for the filtrated water, through which outlet 1a the filtrated water is arranged to be led for further treatment. The outlet 1a is advantageously placed in the filter 4 after the filter material 4a in the direction of motion of the water being treated.

[0080] FIG. 2 presents simplified and diagrammatically the apparatus 10 according to FIG. 1 and, attached to it, a further processing apparatus 11. The further processing apparatus 11 may be of prior art and it may comprise an aeration part 3a for adjusting the oxygen content of the water being treated. In addition, the further processing apparatus 11 may comprise a filter 5 after the aeration part 3a in the direction of motion of the water, which filter 5 comprises, for example, a limestone filter 5a to adjust the pH value of the water being treated. Advantageously, the filters 4 and 5 are connected to each other by, for example, connecting the outlet 1a of the filtrated water in the filter 4 to the inlet of the aeration part 3a of the further processing apparatus 11 with, for example, a suitable piping or channel system. In addition, the filter of the further processing apparatus 11 comprises an outlet 1b, through which the filtrated water is arranged to be led further to subsequent treatment. Advantageously, the outlet 1b is placed in the filter 5 after the filter material 5a in the direction of motion of the water being treated.

[0081] The biological iron and humus removal apparatus 10 presented in FIG. 2 is a modified version of the basic version and comprises a feedback system 7, which is connected between the outlet 1a of the filter 4 and the acidification part 2. The feedback system 7 comprises a measuring element 6 for measuring the pH value of the water, which measuring element 6 also comprises equipment for transmitting the measurement data to the acidification part 2. Correspondingly, the acidification part 2 comprises equipment for receiving the measurement data and for controlling the acidification part 2 based on the measurement data to batch the acid to be added to the water being treated. Advantageously, the amount of the acid to be added is strived to be kept such that the pH value of the water that has filtered through the filter 4 is about 3.1-6.0, advantageously 4.1-4.5, at the outlet 1a of the filter 4. The optimal value is sought case-specifically. FIG. 3 presents diagrammatically and simplified a method according to the invention for removing iron from humus-rich groundwater.

[0082] In the first step s1 of the method according to the invention, the groundwater to be treated is led into the apparatus through the inlet 1, and in the second step s2, into the acidification part 2 to be acidified, where acid is added to the water to lower the alkalinity of the water. Advantageously, the acid to be added is sulphuric acid, but also other acids, such as hydrochloric acid, can be used instead of sulphuric acid. After the acidification, the acidified water is led, in the third step s3, into the aeration part 3, where the oxygen content of the water is measured and adjusted to a desired level. In the fourth step s4, the acidified and aerated water is led further into the filter 4, where the iron and humus of the water being treated are filtered off with the filter material 4a, advantageously sand, inside the filter 4. In the filter 4, the iron is removed from the water as it precipitates when iron bacteria oxidize it biologically and, at the same time, the precipitated iron takes humus with it and both the iron and humus adhere to the filter material 4a. After the filtration, the water being treated is removed from the apparatus 10 in the fifth step s5 through the outlet 1a and is led for further treatment.

[0083] The adjustments of the acidification, aeration, and flow rate of the water are advantageously performed beforehand by measuring in such a way that, when passing through the filter 4, the iron and humus contents and alkalinity of the water, which alkalinity can be measured indirectly with the pH value of the filtrated water, are decreased to the desired values.

[0084] As presented above, the pH value and/or alkalinity of the groundwater being treated is advantageously adjusted to such a level that the pH value of the filtrated water, after the filter 4, is about 3.1-6.0, advantageously 4.1-4.5. Because the iron content in each groundwater is a characteristic for each area and it is not a variable for the operation of this invention, the adjustment of the pH value can be arranged automatically to be essentially unchanged in relation to the flow rate of the water. Thus, the adjustment can be calculated beforehand based on the properties of the water to be treated by, for example, measuring the pH value, iron content, alkalinity, humus content, and flow rate of the water, and by adjusting the acidification and aeration, and the composition and amount of the filter material such that, as a result, filtrated water that is essentially free from iron and humus is obtained, the pH value of which filtrated water is within the desired range. Advantageously, this kind of adjustment that is performed in advance is readjusted occasionally with new measurements and tests.

[0085] If desired, a feedback system 7, which is advantageously connected between the outlet 1a of the filter 4 and the acidification part 2 may be attached to the biological iron and humus removal apparatus 10 according to the invention. In that case, the acidification of the water being treated can be adjusted accurately to obtain filtrated water of uniform quality even if the properties of the incoming water change for some reason or if the filtering properties of the filter material 4a change as a result of use. In that case, the pH value of the water coming out of the outlet 1a of the apparatus 10 is measured and the measurement data is transmitted to the acidification part 2 either continuously or periodically to be used as adjustment data, where in the acidification part 2 the amount of the acid that is added to the water is adjusted based on the measurement results such that, at the outlet 1a of the filter 4, the pH value of the water that has filtered through the filter 4 is, as stably as possible, about 3.1-6.0, advantageously 4.1-4.5.

[0086] The basic idea of the invention is essentially a chemical free biological solution for removing iron and humus, which comprises at its simplest only an acidification step s2, an aeration step s3, and a filtration step s4 without any chemical treatments.

[0087] It is obvious to the person skilled in the art that the invention is not restricted to the examples described above but that it may be varied within the scope of the claims presented below.

[0088] It is also obvious to the person skilled in the art that the filters of the iron removal apparatus and the further processing apparatus may be, for example, filter elements.