JP4579648B2 - Water purification method and water purification device - Google Patents

Description

  The present invention is intended for raw water such as groundwater containing iron, manganese and ammonia nitrogen, and by natural filtration using aerobic microorganisms such as iron bacteria, iron, manganese and ammonia nitrogen contained in raw water such as ground water. The present invention relates to a water purification treatment method and a water purification treatment apparatus for removing water.

  Groundwater often has clean water quality and is a good source of tap water, but it may contain iron, manganese, etc. eluted from rock layers that make up the crust in some areas. Therefore, as a method for removing these substances from raw water such as groundwater containing iron, manganese and ammonia nitrogen, conventionally, aerobic microorganisms such as iron bacteria (iron bacteria having both iron oxidation ability and manganese oxidation ability) and A purification method using a natural filtration method using nitrifying bacteria is known.

  FIG. 5 is an explanatory diagram showing an example of a purification processing apparatus for carrying out a conventional purification processing method. In FIG. 5, reference numeral 1 denotes a raw water adjustment tank to which raw water such as ground water is supplied. Iron bacteria and nitrifying bacteria propagated in the filter layer 8 of the filtration tank 7 described later are aerobic microorganisms and require oxygen, but since groundwater contains almost no dissolved oxygen, aeration of raw water (groundwater), etc. Need to supply oxygen. Therefore, air is sent from the air pump 2 outside the tank to the aeration pipe 4 installed in the raw water adjustment tank 1 and aerated by the aeration pipe 4 so that oxygen is continuously supplied to the raw water in the raw water adjustment tank 1 by aeration. It comes to be supplied. An inverter circuit 3 controls the rotation of the air pump 2. The inverter circuit 3, the air pump 2, and the air diffuser 4 constitute dissolved oxygen supply means for supplying oxygen to the raw water.

  The dissolved oxygen-added raw water supplied with oxygen by aeration is guided to a filtration tank 7 by a dissolved oxygen-added raw water supply pipe 6 having a pump 5, and is directed downward to the filter layer 8 from above the filter layer 8 provided in the filter tank 7. The water is passed in a stream. The filter layer 8 is, for example, a gravel layer 8a, a reference filter sand layer (silica sand layer) 8b for water supply, and anthracite on the perforated block arranged at the bottom of the filtration tank 7, upward from the perforated block. The layers 8c are formed in this order. In addition, as the filter medium for forming the filter layer 8, porous filter media (sintered filter media such as artificial ceramics, natural pumice, etc.), fiber filter media, plastic filter media and the like are employed. While the dissolved oxygen-added raw water guided to the filtration tank 7 passes through the filter layer 8, suspended suspended matters that are turbidity components are suspended and removed at the upper part of the filter layer 8, and in the filter layer 8. By the action of the fermented and supported iron bacteria and nitrifying bacteria, iron, manganese, and ammonia nitrogen contained in the dissolved oxygen-added raw water, that is, contained in the original raw water are removed. The treated water from which these substances have been removed is collected in the water collection chamber of the filtration tank 7 through the perforated block and taken out from the treated water outlet of the water collection chamber.

  By the way, in the purification method by the natural filtration method using the aerobic microorganisms such as iron bacteria and nitrifying bacteria, it is essential to supply oxygen to the aerobic microorganisms in order to maintain stable water purification performance. The management of dissolved oxygen (DO) is important.

  In the conventional purification treatment method, the treated water obtained by passing the dissolved oxygen-added raw water through the filter layer 8 as an index reflecting the quality of removal of iron, manganese and ammonia nitrogen by iron bacteria and nitrifying bacteria. The dissolved oxygen concentration was measured and monitored, and the amount of aeration air blown into the raw water adjustment tank 1 was controlled so that the dissolved oxygen concentration of the treated water became the target dissolved oxygen concentration.

However, according to the experiments by the present inventors, the dissolved oxygen concentration of the treated water has a substantially constant value (for example, about 2 mg / L) regardless of the quality of the water purification treatment effect (regardless of the quality of the obtained treated water). It was. From this, it was found that it is not appropriate to measure the dissolved oxygen concentration of the treated water and adjust and control the amount of aeration air blown into the raw water adjustment tank 1 based on the measurement result. That is, the present inventors have shown from the experiment that when the raw water contains ammonia nitrogen, the raw water is adjusted so that the dissolved oxygen concentration of the treated water becomes the target dissolved oxygen concentration (for example, 2 mg / L or more). Even if the amount of aeration air blown into the tank 1 is controlled, the filtration rate is fast, that is, the contact reaction time with iron bacteria or nitrifying bacteria is not sufficient, and the raw water to which dissolved oxygen is added If the activity of iron bacteria and nitrifying bacteria is low because the dissolved oxygen concentration is lower than the appropriate range, dissolved oxygen will not be properly consumed by the iron bacteria or nitrifying bacteria and will flow out to the treated water side. It has been found that the illusion is that the raw water is sufficiently oxygenated. Thus, the dissolved oxygen concentration raw water is measured and monitored for the dissolved oxygen concentration of the treated water obtained by passing through the filter layer 8 and supplied to the raw water so that the dissolved oxygen concentration of the treated water becomes the target dissolved oxygen concentration. The conventional way of controlling the amount of oxygen has been found to be inappropriate.
Japanese Patent Laid-Open No. 7-100491 (paragraph [0011], FIG. 1) Yutaka Ishimaru, 1 outside, "Purification Water Treatment Technology Using Iron Bacteria Method", Environmental Technology, Environmental Technology Society, April 2004, Vol. 33, No. 4, p. 292-297

  Therefore, an object of the present invention is to target raw water such as groundwater containing iron, manganese and ammonia nitrogen, and to iron, manganese and ammonia nitrogen contained in the raw water by a natural filtration method using aerobic microorganisms such as iron bacteria. In the removal of water, an index that appropriately reflects the quality of the removal state by aerobic microorganisms is measured and monitored, and the amount of oxygen supplied to the raw water is controlled based on the measurement result. An object of the present invention is to provide a water purification treatment method and a water purification treatment apparatus that can stably and satisfactorily remove iron, manganese, and ammonia nitrogen contained therein and stably obtain good water quality.

  In order to solve the above problems, the present invention takes the following technical means.

  The invention according to claim 1 supplies oxygen to raw water such as ground water containing iron, manganese and ammonia nitrogen, and passes the dissolved oxygen-added raw water through a filter layer provided in a filtration tank, thereby providing the filter layer. In the water purification method for obtaining the treated water by removing iron, manganese and ammonia nitrogen contained in the dissolved oxygen-added raw water in the filtration tank by the action of iron bacteria and nitrifying bacteria supported on the filtration tank, Measure the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately before, and supply the raw oxygen water so that the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately before the filter layer becomes the target dissolved oxygen concentration based on the measurement result A water purification method characterized by controlling the amount of oxygen.

  The invention according to claim 2 is the water purification method according to claim 1, wherein the target dissolved oxygen concentration is 5 mg / L or more.

  The invention according to claim 3 is a method in which dissolved oxygen supply means for supplying oxygen to raw water such as ground water containing iron, manganese and ammonia nitrogen, and the dissolved oxygen-added raw water by the dissolved oxygen supply means are passed through the filter layer. The filtration tank for removing the iron, manganese, and ammonia nitrogen contained in the dissolved oxygen-added raw water in the tank by the action of iron bacteria and nitrifying bacteria supported on the filter layer and obtaining the treated water; The dissolved oxygen concentration meter that measures the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately before the layer, and the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately before the filter layer based on the measurement result of the dissolved oxygen concentration target A purification treatment apparatus comprising: dissolved oxygen supply control means for providing a control output to the dissolved oxygen supply means so as to obtain a dissolved oxygen concentration.

  The invention of claim 4 is the water purification apparatus of claim 3, wherein the target dissolved oxygen concentration is 5 mg / L or more.

  The water purification treatment method or the water purification apparatus of the present invention is intended for raw water such as ground water containing iron, manganese and ammonia nitrogen, and iron contained in the raw water by a natural filtration method using aerobic microorganisms such as iron bacteria, When removing manganese and ammoniacal nitrogen, measure the dissolved oxygen concentration of the raw oxygen-added raw water immediately before the filter layer in the filter tank as an index that properly reflects the quality of the removal by aerobic microorganisms. And based on the measurement result, the amount of oxygen supplied to the raw water is controlled so that the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately before the filter layer becomes the target dissolved oxygen concentration. Thereby, iron, manganese, and ammonia nitrogen contained in raw water such as ground water as a tap water source can be stably and satisfactorily removed, and good water quality can be stably obtained.

In the present invention, the dissolved oxygen concentration of dissolved oxygen providing the raw water in the filtrate layer immediately preceding section was measured, so that the dissolved oxygen concentration of dissolved oxygen providing the raw water in the filtrate layer immediately preceding section on the basis of the measurement result is the target dissolved oxygen concentration DO _M The amount of oxygen supplied to the raw water by aeration is controlled. In this case, as the portion immediately before the filter layer for measuring the dissolved oxygen concentration of the dissolved oxygen-added raw water, the position immediately above the filter layer is particularly preferable because it is the closest to the filter layer in the downward flow natural filtration method. And, in the path of the dissolved oxygen-added raw water from the oxygen application to the filter layer, the dissolved oxygen concentration may be a location that is substantially the same with almost no change from the value immediately above the filter layer (Fig. 2).

In the present invention, the target dissolved oxygen concentration DO _M, depending on the filtration rate, it is more 5 mg / L. When the target dissolved oxygen concentration DO _M is below 5 mg / L, oxygen is insufficient in the filtration tank, cleaning effect of iron bacteria and nitrifying bacteria is reduced, iron, stable and good removal of manganese and ammonium nitrogen Can not. Target dissolved oxygen concentration DO _M is preferably 6 mg / L or more, from the viewpoint of obtaining a reliable good processing quality, particularly preferably it is more than 6.5 mg / L. Upper limit of the target dissolved oxygen concentration DO _M, depending on the filtration rate, about 8 mg / L is suitable. The reason is that when the oxygen is supersaturated by excessive aeration, the removal of iron may be deteriorated in raw water containing dissolved silicic acid. In addition, since about 4.6 times the dissolved oxygen is required for nitrification of ammonia nitrogen, the present invention has an ammonia nitrogen concentration of 1.3 mg / L or less (the target dissolved oxygen concentration DO of dissolved oxygen-added raw water). _It is preferable to apply to raw water having a target dissolved oxygen concentration DO _M : 0.6 mg / L or less when the target dissolved oxygen concentration DO _{M is} 5 mg / L when _{M is} 8 mg / L from the viewpoint of reliably removing ammonia nitrogen.

  FIG. 1 is a configuration explanatory view showing an example of a purification treatment apparatus for carrying out the purification treatment method of the present invention. Here, the same parts as those in the conventional purification treatment apparatus shown in FIG. 5 are denoted by the same reference numerals as those in FIG.

As shown in FIG. 1, 9 is a dissolved oxygen concentration meter, which measures the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately above the anthracite layer 8c forming the filter layer 8 of the filtration tank 7. Reference numeral 10 denotes a control device, and the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately above the anthracite layer 8c is set to the target dissolved oxygen concentration DO according to the signal value corresponding to the measured dissolved oxygen concentration value from the dissolved oxygen concentration meter 9. The rotation speed of the air pump 2 is instructed to the inverter circuit 3 so as to be _M. The control device 10 constitutes dissolved oxygen supply control means.

Using the thus configured purification treatment apparatus, the dissolved oxygen concentration meter 9 measures the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately above the anthracite layer 8c, and the control apparatus 10 based on the measurement result. Te so that the dissolved oxygen concentration of dissolved oxygen providing the raw water in the right above the anthracite layer 8c becomes a target dissolved oxygen concentration DO _M, control the amount of oxygen supplied by the aeration in the raw water by adjusting and controlling the rotational speed of the air pump 2 Like to do.

  The treated water obtained is taken out from the treated water outlet of the water collection chamber of the filtration tank 7 and sent to downstream processes such as a rapid filtration process, a biological activated carbon treatment process, or a membrane filtration process as necessary. It has become.

  FIG. 2 is a structural explanatory view showing another example of the purification treatment apparatus for carrying out the purification treatment method of the present invention. Here, the same parts as those in the purification apparatus shown in FIG. 1 are denoted by the same reference numerals as those in FIG.

  As shown in FIG. 2, in this embodiment, two filtration tanks 7 are provided, and the dissolved oxygen-added raw water introduced from the raw water adjustment tank 1 by the dissolved oxygen-added raw water supply main pipe 11 is the dissolved oxygen-added raw water supply. While being introduced into one filtration tank 7 via one branch pipe 12 connected to the main pipe 11, the other filtration tank 7 is connected via the other branch pipe 13 connected to the dissolved oxygen-added raw water supply main pipe 11. To be introduced. Then, as a dissolved oxygen concentration meter that measures the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately before the filter layer 8, in this embodiment, the branch pipe 12 of the dissolved oxygen-added raw water guided by the dissolved oxygen-added raw water supply main pipe 11 is used. , 13 is provided with a dissolved oxygen concentration meter 14 that measures the dissolved oxygen concentration at the branch point.

Using the thus-configured purification apparatus, the dissolved oxygen concentration meter 14 measures the dissolved oxygen concentration of the dissolved oxygen-added raw water at the branch point to the branch pipes 12 and 13 in the dissolved oxygen-added raw water supply main pipe 11. , the control unit 10, as the dissolved oxygen concentration of dissolved oxygen providing the raw water in the branch point based on the measurement result reaches the target dissolved oxygen concentration DO _M, the raw water by adjusting and controlling the rotational speed of the air pump 2 The amount of oxygen supplied by aeration is controlled.

  The present invention is not limited to the embodiment shown in FIGS. 1 and 2, and various design changes can be made without departing from the spirit of the present invention, for example, by providing a dissolved oxygen supply means in the filtration tank 7. It is.

FIG. 3 is a graph showing an example of the result of the water purification treatment according to the present invention. The dissolved oxygen immediately above the anthracite layer of the filtration tank when the filtration rate LV is 130 m / day and the experiment period is about 10 months. The relationship between the dissolved oxygen concentration DO of the raw raw water and each concentration of iron (Fe), manganese (Mn) and ammonia nitrogen (NH ₄ -N) contained in the treated water obtained at the treated water outlet of the filtration tank It is a graph to show. The experiment was performed using the purification treatment apparatus shown in FIG. In addition, each density | concentration of iron, manganese, and ammonia nitrogen contained in raw | natural water is 2.4-24 (average 5.19) mg / L, 0.30-0.41 (average 0.37) mg / L, respectively. L, and 0.48 to 0.83 (average 0.66) mg / L.

As understood from FIG. 3, the filtration rate LV: For 130m / day, if the target dissolved oxygen concentration DO _M to perform the water purification process as 7~8mg / L, iron: 0.4 mg / L or so, It was confirmed that good water purification treatment could be performed stably such as manganese: less than 0.1 mg / L and ammoniacal nitrogen: less than 0.01.

FIG. 4 is a graph showing an example of the result of the water purification treatment according to the present invention, and the dissolved oxygen immediately above the anthracite layer of the filtration tank when the filtration rate LV is 65 m / day and the experiment period is about 7 months. The relationship between the dissolved oxygen concentration DO of the raw raw water and each concentration of iron (Fe), manganese (Mn) and ammonia nitrogen (NH ₄ -N) contained in the treated water obtained at the treated water outlet of the filtration tank It is a graph to show. The experiment was performed using the purification treatment apparatus shown in FIG. In addition, each density | concentration of iron, manganese, and ammonia nitrogen contained in raw | natural water is 2.4-24 (average 5.19) mg / L, 0.30-0.41 (average 0.37) mg / L, respectively. L, and 0.48 to 0.83 (average 0.66) mg / L.

As understood from FIG. 4, the filtration rate LV: For 65 m / day, if the target dissolved oxygen concentration DO _M to perform the water purification process as 6~8mg / L, iron: 0.3 mg / L or so, It was confirmed that a good water purification treatment could be performed stably such as manganese: less than 0.001 mg / L and ammoniacal nitrogen: less than 0.01 mg / L.

It is composition explanatory drawing which shows an example of the purification processing apparatus for enforcing the purification processing method of this invention. It is composition explanatory drawing which shows another example of the purification processing apparatus for enforcing the purification processing method of this invention. It is a graph which shows an example of the water purification process result which concerns on this invention. It is a graph which shows an example of the water purification process result which concerns on this invention. It is composition explanatory drawing which shows an example of the purification processing apparatus for enforcing the conventional purification processing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Raw water adjustment tank 2 ... Air pump 3 ... Inverter circuit 4 ... Aeration pipe 5 ... Pump 6 ... Dissolved oxygen provision raw water supply pipe 7 ... Filtration tank 8 ... Filtration layer 8a ... Gravel layer 8b ... Standard filtration sand layer 8c ... Anthracite Layers 9, 14 ... Dissolved oxygen concentration meter 10 ... Control device 11 ... Dissolved oxygen-added raw water supply main pipe 12, 13 ... Branch pipe

Claims (4)

  By supplying oxygen to raw water such as groundwater containing iron, manganese, and ammonia nitrogen, and passing this dissolved oxygen-added raw water through a filter layer provided in a filter tank, iron bacteria supported on the filter layer and In the water purification method for removing iron, manganese and ammonia nitrogen contained in the dissolved oxygen-added raw water in the filtration tank by the action of nitrifying bacteria and obtaining the treated water, the dissolved oxygen-added raw water immediately before the filter layer And measuring the amount of oxygen supplied to the raw water so that the dissolved oxygen concentration of the dissolved oxygen-added raw water immediately before the filter layer becomes the target dissolved oxygen concentration based on the measurement result. Characterized water treatment method.   The water purification method according to claim 1, wherein the target dissolved oxygen concentration is 5 mg / L or more.   The dissolved oxygen supply means for supplying oxygen to the raw water such as ground water containing iron, manganese and ammonia nitrogen, and the dissolved oxygen-added raw water by the dissolved oxygen supply means are passed through the filter bed, thereby being supported on the filter bed. By the action of iron bacteria and nitrifying bacteria, iron, manganese, and ammonia nitrogen contained in the dissolved oxygen-added raw water in the tank are removed to obtain treated water, and dissolved oxygen immediately before the filter layer. The dissolved oxygen concentration meter that measures the dissolved oxygen concentration of the raw raw water, and the dissolved oxygen concentration of the raw oxygen-added raw water in the immediately preceding portion of the filter bed based on the measurement result by the dissolved oxygen concentration meter becomes the target dissolved oxygen concentration A purification treatment apparatus comprising: dissolved oxygen supply control means for supplying a control output to the dissolved oxygen supply means.   The water purification apparatus according to claim 3, wherein the target dissolved oxygen concentration is 5 mg / L or more.

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