DE4024529A1 - Treating water contg. organic matter and nitrate, giving potable water - by ozone treatment giving assimilable cpds., and filtering through two layer fixed bed contg. heterotrophic microorganism - Google Patents

Abstract

Water treatment comprises: (a) intense treatment with O3, giving direct mineralisation of part of the organic substances and breaking down part to low-mol. and assimilable organic gas., (b) passing the O3-treated water through a fixed bed reactor with an upper, O3-reducing coarse layer of filter C, and a lower filter bed of fine sand to separate the water, contg. solid particles, into solid and liq. The fixed bed reactor contains a heterotrophic microorganism which assimilates the organic low-mol. prods. of the O3 treatment and breathes The mol. O2 in the water, leading to a deficit in mol.O2. The process is continued until, as a result of the consumption of mol. O2. redn. or breakdown of nitrate occurs because of further breakdown of organic, low-mol. substances still present, by extn. of O from nitrate by the microorganism. There may be a further disinfection stage with more O3 after the active C filtration. The process of nitrate breakdown by extn. of O from the nitrate by the microorganism can be prolonged by addn. of nutrients to the raw water before the O3 treatment; the duration of the process and thus the breakdown of nitrate are then determined by the amt. of assimilable low mol. organic substances remaining available. USE/ADVANTAGE - For prepn. of rotable water from ground, spring or surface water contaminated by nitrates and organics, at levels too low for enzymatic splitting without external influence.

Description

I. State of the art 1. The problem

Not least due to intensified agriculture and the associated To date, over-fertilization has been a constant increase in Determine nitrate concentration in the groundwater. The Drinking Water Ordinance (TVO) allows maximum nitrate Concentration of 50 mg / l and gives 25 mg / l as a guideline.

The reduction of the previous limit of 90 mg / l to now 50 mg / l forces a variety of water supply Companies either no longer have existing water resources or only can still be used as mixed water for low-nitrate water or install nitrate reducing treatment systems.

2. Nitrate reduction

The following options are currently known for nitrate reduction:

2.1. Physically
2.1.1. Ion exchanger
2.1.2. Membrane filtration
2.2. Biotechnical
2.2.1. autotrophic denitrification
2.2.2. heterotrophic denitrification

2.1. Physically

Physical processes cause nitrate separation, however in in no case its reduction. It can only be used by one Nitrate shift spoken from one system to another will.

2.1.1. Ion exchanger

Processes with ion exchangers require regeneration. in the Cycle, the cation exchanger removes the hardening agents Calcium and magnesium and releases hydrogen ions. In parallel the anion exchanger exchanges sulfate, nitrate and chloride ions Raw water against hydrogen carbonate ions. The procedure brings thus not only a significant salt load in the sewage system, but also removes - since it does not work selectively - the nitrate also a significant amount of desired minerals from the drinking water.

2.1.2. Membrane filtration

The membrane filtration works with the osmotic pressure and one semi-permeable membrane. This is also disadvantageous not NO₃-specific way of working, the high energy requirement and absolutely necessary water treatment. The disadvantage is also that - as with the ion exchanger - the nitrate in its form remains and thus also only a problem shift he follows.

2.2. Biotechnical

In the case of biotechnical denitrification, the one belonging to the nitrate Exhale oxygen naturally or as an electron acceptor used. The released nitrogen (N₂) is gaseous and can be released into the atmosphere. A distinction must be made between the autotrophic and the heterotrophic Denitrification.

2.2.1. Autotrophic denitrification

In autotrophic dentrification, the bacteria required energy through the oxidation of inorganic materials and generated from molecular hydrogen.

This provides the oxygen required for the oxidation Nitrate containing water. The autotrophic process works reliably, does not require the addition of nutrients and reduces the risk net germination to a minimum.

For the purpose of oxygen enrichment and the necessary disposal of nitrite (NO₂) that may have arisen in the process is in post-processing is always required. Another disadvantage is the security risk from using atomic hydrogen and which are especially in smaller plants resulting high cost.  

2.2.2. Heterotrophic denitrification

The heterotrophic denitrification largely corresponds to the natural one Process of nitrate reduction in an aquifer.

Denitrifiers are aerobic bacteria of various kinds, required an organic carbon source for energy production and Phosphate as a process-accompanying substance. The one for mineralization Oxygen required from the carbon source is taken from the nitrate. This creates - as with autotrophic denitrification - Gaseous nitrogen (N₂).

In heterotrophic denitrification, biological Degradation of organic substances or their mineralization of natural ones Way in three stages:

In stage 1, the enzymatic splitting of high molecular weight takes place organic compounds to assimilable low molecular weight Groups.

In stage 2, the assimilable groups for energy generation and further broken down to build up cell-own substance.

In level 3, the remaining substances from level 2, e.g. B. activated acetic acid, completely mineralized.

The heterotrophic process is due to the diversity of the process involved bacteria relatively insensitive as a nutrient and that Problem of residual values in pure water leading to re-germination.

Like autotrophic denitrification, heterotrophic also requires In any case, denitrification for the purpose of water treatment Oxygen enrichment, nitrite removal and with special Focus on eliminating residual assimilable carbon.

Biological denitrification uses nitrate without the water type further change, selectively removed from the water cycle. The nitrate reduction takes place in the following steps:

NO₃ ^- → NO₂ ^- → N₂O ^- → N₂

II. Description of the Invention: (Hydrozone Process) 3. Biological nitrate reduction through pre-zoning

Process scheme of the process:

3.1. Pre-zoning

The nitrate reduction by pre-zoning also requires the biological one Process. In contrast to 2.2.2. described heterotrophic denitrification uses the HYDROZON method in primarily the organic compounds contained in the raw water as a source of nutrients. This is possible through intensive Raw water ozone treatment of high molecular weight organic substances oxidized into low molecular weight and thus assimilable compounds will.

3.2. Mixed bed filter

In the mixed bed filter following the ozone treatment, the rest of the Water still dissolved ozone - through the filter coal - in the top Part of the filter bed eliminated. In addition, the filter is carried out Deposition of corpuscular particles and the assimilative Removal of dissolved substances by aerobic bacteria. Here is brought in by intensive ozone treatment or ventilation Oxygen, if required, is breathed in and thus consumed.

3.3. Activated carbon filter

The activated carbon filter downstream of the mixed bed filter is, and again depending on the nutrient supply, especially biologically activated. As long as there is a further oxygen Consumption up to the - by exposure to ozone from high molecular weight organic compounds - assimilable substances are used up.

With organic matter still present and reduced oxygen saturation the nitrate oxygen is forcibly Acceptor of the heterotrophic, in the activated carbon filter bed settled microbes accepted and thus exhaled. The process thus corresponds to heterotrophic denitrification, but with the difference that the electron donor, i.e. H. the Nutrient source, mainly the natural organic load comes from the raw water.

Limiting factor in the biological nitrate reduction by Pre-zoning is the organic cargo, the efficiency of the ozone treatment and the formation of the filter (s) as biologically active Fixed bed reactor. Here, those coming from the raw water and brought into the assimilable form by the action of ozone organic compounds largely used up. With the addition of organic substances - before the ozone treatment - The quantitative performance of the Nitrate reduction can be expanded.

The division of the fixed bed reactor into two separate systems optimizes the process. The mixed bed filter as the first biological The stage can be backwashed any number of times without the overall process essentially disrupting. The task of the mixed bed filter is in primarily the removal of filterable substances. The activated carbon filter has the task of eliminating the remaining assimilable substance at the same time Consumption of nitrate oxygen and the associated Denitrification.  

3.4. Final zoning

Powered by the final disinfection facility from the exhaust air with residual ozone from the oxidation stage at the same time the required oxygen enrichment and the Removal of any nitrite from the process.

Results from advanced process engineering

The pictures above show photometric or spectrophotometric determined results from a HYDROZON water Processing plant with advanced process technology. Except for the shown degradation performance is in particular the stability of the Pure water after the final zoning.

Claims (3)

1.Procedure for the treatment of groundwater, spring water or surface water contaminated with organic and nitrate for the purpose of obtaining drinking water in accordance with applicable regulations, the organic load of which is so low and / or designed that an enzymatic breakdown does not take place without external influence, be characterized in that the water an intense ozone treatment is subjected to, said part directly mineralized by the high oxidizing power and high oxidizing action of the ozone, the organic substances contained in the water as far as possible split to the other part in low molecular weight and assimilable organic groups that the water treated with ozone can be fed to a subsequent fixed bed reactor designed as a mixed bed, with an upper, ozone-reducing, coarse filter layer consisting of filter coals, with an underlying fine sand filter bed for separating the solid particles ten water in solid and liquid, with a heterotrophic microorganism in the fixed bed reactor which assimilates the organic, low-molecular substances produced by the influence of ozone and thereby breathes the molecular oxygen contained in the water, an increasing deficit of molecular oxygen being established and occurring during the course of the process that the process section is carried out to such an extent that when the molecular oxygen is largely consumed, the water is reduced or reduced by means of a further decomposition of the organic, low-molecular substances still present by the microorganism exhaling the oxygen belonging to the nitrate. 2. The method according to claim 1, characterized in that that the filtration stage with activated carbon is another Disinfection stage with another ozone treatment is connected downstream. 3. The method according to claim 1 or 2, characterized characterized in that to extend the processor of the Nitrate degradation by exhaling the nitrate oxygen the microorganism, the raw water additional nutrient is added before the oxidation stage with ozone treatment, the process duration and thus the nitrate breakdown by the available amount of assimilable low molecular weight organic substances is determined.