DK167755B1 - PROCEDURES FOR BIOLOGICAL TREATMENT OF WASTE WATER WITH AN INCREASED SHARE OF NITROGEN COMPOUNDS - Google Patents

Description

DK 167755 B1

The present invention relates to a process for the biological treatment of wastewater with an increased proportion of nitrogen compounds, by which the oxygen content (p02) of the wastewater is measured and reduced per liter. time unit breathed 5 airflow with increasing oxygen content.

In addition to the known impurities, wastewater may also contain nitrogen compounds as wastewater constituents at various concentrations. These nitrogen compounds, e.g. egg whites, amines, ureas, ammonium salts, 10 nitrites and / or nitrates, strain the sewage drains due to their high oxygen demand, their eutrophication effect and the possibly toxic effects. Thus, the elimination of these wastewater constituents is becoming increasingly important.

From published international patent application WO 86/03734, a method for biological wastewater treatment with nitrification and denitrification is known, in which the air supply and the amount of air are regulated depending on the amount of oxygen dissolved in the wastewater.

20 From Korespondenz Abwasser 34 (1987), page 80, an activation method with intermittent denitrification is known.

In this process, there is no pronounced separation of nitrification zone and denitrification zone. The nitrogen compounds are eliminated in sub-steps. In a first sub-step, the nitrogen in the organics is microbially converted to ammonium to a large extent. The ammonium is the starting point for a biochemical nitrification, in which in an aerobic environment with e.g. Nitrosamonase species according to Equation 30 NH 4 + + 1.5 O 2 -> NO 2 ~ + 2 H + + H 2 O are converted to nitrite and the nitrite with e.g. Nitrobacter species according to the equation NO2 "+ 0.5 02 -> NO3 ~ 35

Ul / ΙΟ / 09 D l 2 is converted to nitrate. As nitrification is released, hydrogen ions are released / lowered, until eventually a value capable of destroying the total biological purification process is obtained. The metabolism of nitrates is optimal in the pH range from 7 to above 8. Finally, in a further sub-step, the nitrite and nitrate in the anoxic environment are reduced with optional anaerobic heterotrophic bacterial genera, e.g. Achromobacter, Denitrobacillus or Pseudomonas, to N2.

The OHs obtained by this reaction increase the pH.

10 Denitrification is regulated by measuring the NOx content. Since the NOx measurement is technically cumbersome and thus readily associated with genes, it is the object of the present invention to provide a method control that functions reliably and permits optimal execution of this particular biological method.

This object is achieved according to the invention by a method of the above-mentioned nature, which is characterized by allowing air in a publisher of wastewater and activated sludge, interrupting the air supply after reaching a predetermined minimum pH, taking out a certain amount of sludge -water mixture, which then supplies an equivalent amount of fresh wastewater and after reaching a predetermined maximum pH again re-enters air and reflux sludge.

The biological treatment is conveniently carried out between 5 ° C and 50 ° C. The air supply can be controlled by measuring the pH values, the pH value being suitably kept between 5 and 10. The amount of air available at any time can be controlled via the oxygen content of the sludge-water mixture. The sludge-water mixture can also be removed continuously during treatment, and the equivalent amount of fresh wastewater can be fed continuously.

The process according to the invention has the following advantages: The process can be regulated over the pH by starting and interrupting the air supply and kept in the optimum range. Without special addition of acid or base, the desired pH range can be observed. Nitrification and denitrification work optimally, ie. without inhibition at extreme pH values in the activation environment. The aerobic and anoxic phase can be changed in the opposite direction during one operation. This makes it possible to better adapt the process process to the received COD and nitrogen load. The denitrification process is accelerated by the shock supply of fresh wastewater during the anoxic phase. The nitrates undergo the anoxic phase unimpaired and resume the nitrification process as soon as sufficient oxygen is dissolved in the wastewater. As all processes are carried out in the same publishing house, the return of large quantities of sludge and effluent water is avoided.

The process of the invention is further illustrated in the following example.

Example

Sewage that appears in the animal husbandry area - approx. 40 m3 a day - has the following characteristics: pH-value 8-10 20 B0D5 approx. 10,000 g 02 / m3 COD approx. 18,000 g of 02 / m3

Nitrogen containing compounds approx. 1,900 g-N / m3, thereof

Ammonium (NH4 +) Compounds approx. 1,500 g N / m3

Nitrite (N02 “) - compounds 10 g N / m3 25 Nitrate (Ν02“) - compounds 1 g N / m3

The wastewater is treated in an activation tank of 200 m 3 according to Figure 1 of the drawing at a temperature between 20 and 25 ° C according to the method illustrated schematically according to Figure 2 in the drawing. The concentration of active sludge, measured as dry mass of the sludge (TS), is approx. 10-12 kg / m3, of which approx. 7 to 9 kg / m3 is organic mass (TSorg) ·

The wastewater is supplied continuously for 5-6 periods per day. day 35 in volumes at each time approx. 6-8 m3. The average residence time is approx. 5 days. This creates a room load-

UIV ΙΟ // OO D I

4 kg of BOD5 / m3 or 3.6 kg of COD / m3 day.

For a period of approx. 4-5 hours, 40 to 50% fall on the anoxic phase. The rest of the time is aired. Hereby the pH fluctuates between 7.5 and 8.

The sludge has a sludge index of 70 to 100 l / kg, i.e. after a 30 minute deposition time, from 70 to 100 l of sludge containing 1 kg of dry mass is obtained. The sludge can be easily separated. The resulting sludge fluctuates with the value of approx. 50 kg dry mass per day.

10 After decanting, the following effluent values are found in the treated wastewater: BODg 20 - 60 g O2 / m3 COD 500 - 600 g o2 / m3 NH4 + 3 - 10 g N / m3 N02 "1 g N / m3 N03". 2 - 5 g N / m3

This corresponds to an elimination rate of 20 B0D5 approx. 99% COD approx. 97%

Nitrogen containing compounds approx. 98% Figure 1 shows the apparatus used in the schematic embodiment and Figure 2 shows the process of the biological treatment in the schematic embodiment. Herein, 1 denotes a publishing house, 2 denotes a clearing vessel, 5 denotes a line for the sludge-water mixture, 3 denotes a line for the backflow sludge, 4 denotes a line for fresh wastewater and air supply, and 6 denotes a line for ready-fluid drain. In Figure 2, the amount of supplied air is given as VL, the amount of the supplied or discharged liquids is given as Vp ^ (fresh water Z, sludge-water mixture S and reflux sludge RS), the dissolved O₂ amount is indicated as p02. , and the pH value is given over time. D denotes the tricycle and B + N indicates the activation and nitrification cycle.

Claims (3)

6 UK lb // bb κι 1. A method for the biological treatment of wastewater with an increased proportion of nitrogen compounds, by which the oxygen content (PO2) of the wastewater is measured and reduced to 5 per cent. unit of air blown in with increasing oxygen content, characterized by admitting air in a waste water and activated sludge publisher, interrupting the air supply after reaching a predetermined minimum pH, taking out a certain amount of sludge-water mixture and then adding an equivalent amount of fresh sewage and after reaching a predetermined maximum pH again re-enters air and reflux sludge. Process according to claim 1, characterized in that the biological treatment is carried out at 15 temperatures between 5 and 50 ° C. Process according to claim 1, characterized in that the specified amount of sludge-water mixture during the treatment is taken out continuously and the equivalent amount of fresh sewage is fed continuously.