RU2322399C1 - Process of cleaning waste waters to remove ammonium salts, nitrates, and nitrites - Google Patents

Abstract

FIELD: waste water treatment.

SUBSTANCE: process comprises treatment of water with activated sludge in air tanks and secondary settlers and post-treatment of water by contacting it with higher aquatic plant, in particular water-immersed Vallisneria spirlis. Post-treatment is carried out simultaneously with treatment in secondary settlers. Density of plant growth is 7-14 kg in 1 m³ of structure volume. At waste water intake 11 m³ per 1 m³ of piscine, 1 m³ of plant daily absorbs 2.71 g nitrogenous substances.

EFFECT: enhanced waste water treatment efficiency.

2 tbl, 2 ex

Description

The invention relates to methods for wastewater treatment and can be used at small and large treatment plants and post-treatment of urban wastewater.

A known method of wastewater treatment, involving the treatment of water with activated sludge in aeration tanks and secondary sumps, followed by its purification by contact with a higher aquatic plant - cyperus alternifolia (Cyperus alternifolius) in the flow channel. The flow rate of wastewater in the flow channel is set to 100 l / (day · m ³ ), the water temperature in the channel is maintained in the range of 12-25 ° C, and every 20 days 15% of cyperus biomass is removed from the channel [1].

The disadvantage of this method is the impossibility of its use in the cold season. In order to create the next-leaf ambient temperature optimal for the development of cyperus in the cold season, it is necessary to build special treatment facilities for the greenhouse type.

The closest in technical essence to the proposed is a method of wastewater treatment by treating water with activated sludge in aeration tanks and secondary sumps, followed by its purification by contact with a higher water plant in the flow channel. As a higher water plant, fine-toothed mollusk (Najas microdon) is used. The flow rate of wastewater in the flow channel is established based on the condition that 1 kg of plant weight accounts for about 2.4 g of nitrogenous substances and 0.5 g of phosphates per day, and the water temperature in the channel is maintained at 12-20 ° С, every 20 days from the pool remove 15% of the biomass of finely toothed mollusk [2].

The main disadvantages of this method include the complexity of its application at large stations. When using finely toothed mollusks, the maximum absorption rate of pollutants is manifested when the wastewater flow rate is 24 m ³ / day per 1 m ^{3 of the} flow channel. However, for large treatment plants this technological parameter is difficult to establish, because this will require a decrease in the productivity of structures or an increase in the volume of the flow channel. At large stations, the wastewater flow rate is more than 40 m ³ / day per 1 m ^{3 of the} flow channel. With this flow rate, the speed of movement of wastewater increases significantly and, accordingly, the removal of mollusk plants occurs, which leads to a decrease in the efficiency of wastewater treatment. At small stations, the disadvantage is the high density of the growth of fine-toothed mollusk plants (1 m ³ of the pool volume is 2 times higher than in the proposed method), as a result of which it occupies a large volume of the open channel working area, which leads to a decrease in wastewater consumption and lower efficiency the cleaning process.

The objective of the invention is to increase the efficiency of the process of treating municipal wastewater from ammonium salts, nitrates and nitrites at small and large treatment plants.

The problem was solved due to the fact that in the known method of treating wastewater from ammonium salts, nitrates and nitrites by treating water with activated sludge in aeration tanks and secondary settling tanks and purifying it by contact with a higher aquatic plant, the water is being treated simultaneously with secondary sedimentation tanks. As a higher water plant, a spiral vallisneria (Vallisneria spiralis), completely immersed in the water column, is used at a plant growth density of 7-14 kg per 1 m ^{3 of the} volume of the structure. The flow rate of wastewater is determined based on the condition that 1 kg of the plant mass absorbs about 2.71 g of nitrogenous substances.

Vallisneria spiralis (Vallisneria spiralis) is an evergreen perennial plant with creeping rhizome and ribbon-like leaves. The leaves reach a length of up to 50-60 cm and are collected by bushes, from which shoots with young plants - "mustache" (up to 50 pcs. Per year) depart. The plant is unpretentious in terms of water temperature ((+14) - (+ 25) ° C), the reaction of the aquatic environment (pH 5-7), soil and light. To plant a plant, you can use a sand-gravel mixture. The thickness of the soil layer may be small, 2-3 cm is enough.

Vallisneria spiral supplies water with oxygen and takes an active part in the cycle of organic and inorganic substances in water. The plant maintains its vitality even when in water under a layer of ice on the surface of the pool.

The cleaning method is as follows.

Urban wastewater that has been treated in activated sludge aeration tanks is discharged into secondary sumps. In sedimentation tanks, plants of spiral wallisneria are planted. The plant growth density is 7-14 kg in 1 m ³ of the pool volume. As the water moves, the Wallysneria plants absorb the ammonium salts, nitrates and nitrites dissolved in it that are not recoverable by the biological treatment system. The wastewater flow rate is determined on the basis of the condition that about 2.71 g of nitrogenous substances per day per 1 kg of plant mass.

The facilities are operated year-round, subject to the optimal temperature for plants from + 14 ° С to + 25 ° С. The necessary temperature regime is ensured by the temperature regime of wastewater, which fluctuates during the year from + 12 ° C to + 26 ° C. Since the warm wastewater surrounding the stems of the plants immersed in it from all sides supports the temperature regime necessary for their vital functions, the construction of greenhouse-type structures is no longer necessary.

Example 1. Biologically purified water from the aeration tank system was supplied to the secondary sumps, where after separation of the water-sludge mixture when the wastewater came into contact with spiral valine-energy, nitrogen salts were purified.

The plant growth density is 14 kg in 1 m ³ of the pool volume. Wastewater flow rate was set to 11; 7; 6 m ³ per day for 1 m ^{3 of the} pool.

The results of the intensity of absorption by Walsneria of spiral nitrogen salts are shown in table 1.

From table 1 it is seen that the maximum intensity of the absorption of vallisneria spiral manifests when feeding 11 m ³ waste water per 1 m ³ pool. At the indicated flow rate, the sludge of activated sludge in the sump and separation of the water-sludge mixture are ensured; at a higher flow rate, the active sludge is removed along with the liquid flow. Therefore, this load should be considered optimal, and the intensity of absorption of nitrogenous substances is about 0.113 g / kg / hour or 2.71 g / kg / day.

Example 2. Biologically purified wastewater and secondary sumps wastewater was subjected to purification by contact with spiral wallisneria in secondary sumps (the inventive method), and also fed into the flow channel, which was planted with fine-tooth moth (prototype). The density of the live weight of the spiral wallisneria was chosen to be 2 times lower than the mollusk, the waste water temperature is identical. The wastewater flow rate is the same. The results of comparing the absorption intensity are shown in table 2.

From table 2 it is seen that in the spiral wallisneria at a lower plant growth density, the absorption rate of nitrogen compounds is higher than that of the finely toothed mollusk, by 88%.

Table 1
Vallisneria Absorption Rate of Nitrogen Salts Indicators The average concentration, mg / l Sewage consumption per 1 m ^{3 of the} structure (m ³ / day) eleven 7 6 Absorption rate, g / kg per hour N-NH ₄ 2.2 0.05 0,0259 0,0256 N-NO ₃ 11.8 0.0625 0,035 0,035 N-NO ₂ 0.13 0,00142 0.0013 0.0013 ∑ forms of nitrogen 14.13 0.113 0,062 0.0625

table 2
The intensity of absorption of nitrogen salts by various plants with a wastewater flow rate of 11-12 m ³ / day Indicators The absorption rate of 1 kg of live weight of plants, g / hour Wallisneria Naiad NH ₄ ⁺ 0.05 0.005 NO ₃ ^- 0.0625 0.0582 NO ₂ ^- 0,00142 0.00052 ∑ forms of nitrogen 0.113 0.06

The proposed method of wastewater treatment will reduce the flow of nitrogen salts into the body of water with purified wastewater, which will reduce the "bloom" of water, prevent the death of aquatic flora and fauna and improve its chemical composition.

Information sources

1. Copyright certificate No. 1719320, IPC ⁵ C02F 3/32, 1992.

2. RF patent No. 2081852, IPC ⁶ C02F 3/32, 1997.

Claims (1)

A method of treating wastewater from ammonium salts, nitrates and nitrites by treating water with activated sludge in aeration tanks and secondary sumps and purifying it by contact with a higher aquatic plant, characterized in that the post-treatment of water by contact with a higher aquatic plant is carried out simultaneously with secondary sedimentation tanks, as higher plants use water vallisneria spiral (Vallisneria spiralis) completely immersed in the waste water during growth of density 7-14 kg per 1 m ³ of volume structure, and the flow rate stochno water was adjusted based on the condition that 1 kg of the plant absorbs about 2.71 g of nitrogenous substances per day.