RU2796677C1 - Method for wastewater biological treatment - Google Patents

Abstract

FIELD: biotechnology.

SUBSTANCE: method for the biological treatment of quarry wastewater is proposed, including the supply of wastewater to a spatially separated cascade filter, composed of sections through which the water to be purified is sequentially supplied, in the first section, mechanical purification from impurities and suspended solids is carried out due to a filtration partition - a fine-mesh membrane with a size pores not less than 10 µm, in the second section there are broad-leaved cattail Typha latifolia L., common water plantain Alisma plantago-aquatica L. and jointed rush Juncus articulatus L.; in the third section - Chlorella microalgae; in the fourth section, settling and further discharge into a water body are carried out; fine-mesh membranes with a pore size of at least 8 μm are used as the second and third filtration partitions; the period of stay of career wastewater in the treatment plant is 3-5 days.

EFFECT: extension of the range of methods for biological treatment of quarry wastewater using additive effect of higher and lower aquatic vegetation.

1 cl, 4 tbl, 3 ex

Description

The invention relates to the field of environmental protection and can be used for biological wastewater treatment.

A known method of hydrobotanical purification of polluted aquatic environments in climatic conditions of mid-latitudes (RF patent 2288894, publ. 10.12.2006), including the use of Eichhornia as a hydrobotanical zone floating in the nutrient solution, and using sewage, household or industrial water as a nutrient solution, at the same time, the vegetation of Eichornia is carried out at an ambient air and water temperature of at least 19 ° C with natural and / or artificial lighting.

The disadvantage of this method is the limitation of the scope of the temperature conditions of the middle latitudes and secondary pollution during the stirring of silt deposits.

There is a known method of biological post-treatment of wastewater (RF patent 2186738, publ. 08/10/2002), including the contact of wastewater with higher aquatic vegetation in flowing conditions, while wastewater is supplied to a uniform layer of a bioplato limited by a drainage shaft through a water distribution channel laid along the root bank floodplains along the length of the bioplateau, which is used as a floodplain swamp or swampy floodplain meadow.

The disadvantage of this method is the removal of a large area for the bioplateau and the limited use only by the presence of wetlands.

A known method of biological post-treatment of wastewater and a system for its implementation (RF patent 2504519, publ. 20.01.2014), which consists in the fact that the biological post-treatment of wastewater is carried out in treatment modules in the form of covered ponds 4-5 times longer than the width, having insulation from the inside of the shelter, in each of which fertile soil is laid for planting reed strips, between which the Lesser Duckweed is in a free-floating state.

The disadvantage of this method is the secondary contamination of treated water in terms of BOD ₅ .

There is a known method for post-treatment of wastewater (RF patent 2530173, publ. 10.10.2014), including the use of plantings of lake reed Scirpus lacusrtis L. , cattail Typha angustifolia L. and Canadian elodea Elodea canadensis Michx planted on a plot of equipped terrain, characterized in that in the process of post-treatment, the wastewater flow additionally passes through at least three structured zones "open reach-thickets of plants", in each of which there are plantings of lake reeds of the first row and cattail of the narrow-leaved second row of a two-row non-linear arc, curved along the stream in the lower part of the reach, in combination with plantings of Canadian elodea on the sides of the stream, they form a central closed zone with a space free from plantings.

The disadvantage of this method is the need to periodically remove part of the overgrown vegetation in order to restore the structured zones and the central free zone of the treatment plant.

A known method for the complex treatment of complex multicomponent wastewater (RF patent No. 2758690, publ. 11/01/2021), adopted as a prototype, including the supply of wastewater to a spatially separated cascade filter, composed of at least three biomodules, which are shallow pools, in the first of which placed loads with immobilized bacterial biocenosis, in the second - loads with immobilized associations of microalgae, in the third - loose higher aquatic vegetation, which is used as hornwort and Canadian elodea.

The disadvantage of this method is the low productivity and secondary contamination of purified water as a result of the introduction of degrading microorganisms and microalgae from the purification system.

The technical result is to increase the efficiency of wastewater treatment.

The technical result is achieved by the fact that previously in the first section mechanical cleaning of impurities and large suspended solids is carried out, due to the low flow rate and under the action of gravity, and a filtration partition is used, which is used as a fine-mesh membrane with a pore size smaller than the size of the expected purification of mechanical impurities and suspended particles, then the water overflows into the second section, where plantings are located, which are used as broad-leaved cattail Typha latifolia L., common chastukha Alisma plantago-aquatica L. and jointed rush Juncus articulatus L., during the flow of waste water through them, fine suspended solids are deposited, then the wastewater flows through the second filtering partition, which is made of a fine-mesh membrane with a pore size smaller than the size of microalgae cells, into the third section, and then the wastewater flows through the third filtering partition, which is made of a fine-mesh membrane with a pore size less than the size of microalgae cells, into the fourth section, where settling and further discharge into the water body takes place.

The method is carried out as follows. A functioning treatment plant - a settling pond or a storage pond is divided by three filtering partitions into four sections, and the pore size of the first partition is determined by the size of mechanical impurities and suspended particles intended for cleaning, but not less than 10 microns. The pore size of the second partition is determined by the size of the cells of the introduced microalgae to exclude their entry into the second section, but not less than 8 microns. The pore size of the third partition is determined by the size of the cells of the introduced microalgae to exclude their removal with purified water into the fourth section, but not less than 8 microns.

Wastewater entering the treatment enters the first section of the treatment plant. At a low flow rate of wastewater, its transporting capacity of mechanical impurities and suspended solids decreases in the horizontal direction. Sedimentation of mechanical impurities and large suspended solids is carried out under the action of gravity within the length of the first section of the treatment plant. Further, the wastewater passes through the filtering partition between the first and second sections, where additional sedimentation of mechanical impurities and suspended particles takes place. The filtering partition between the first and second sections, which is a fine-mesh membrane with a pore size smaller than the size of mechanical impurities and suspended particles intended for purification, to capture particles due to inertial collision, adhesion and adsorption.

Further, wastewater enters the second section of the treatment plant for biological treatment. In the process of the flow of waste water into the second section, the distribution of waste water occurs over the volume of the second section, where plantings of broad-leaved cattail Typha latifolia L., common chastukha Alisma plantago-aquatica L. and jointed rush Juncus articulatus L. are located. These species are distinguished by a wide distribution area, unpretentiousness to climatic conditions. In the process of flowing wastewater through the planted vegetation, fine suspended solids are deposited that are not captured in the first section of the treatment plant.

From the second section of the treatment plant, the wastewater, passing through the filtering partition between the second and third sections, where Chlorella microalgae cells are prevented from entering the second section, enters the third section of the treatment plant. The filtering partition between the second and third sections is a fine-membrane membrane with a pore size smaller than the cell size of the Chlorella microalgae strain.

In the third section of the treatment plant, lower aquatic vegetation is introduced - a strain of Chlorella microalgae to create a biogeocenosis with naturally developing communities of microalgae and bacteria for the complex purification of pollutants due to the additive effect of higher and lower aquatic vegetation. The introduction of a strain of microalgae Chlorella is carried out in wastewater that is already being treated in a functioning treatment plant.

Further, wastewater passes through the third filtering partition, which is a fine-mesh membrane with a pore size smaller than the cell size of the applied microalgae Chlorella strain, to capture microalgae cells due to inertial collision, adhesion and adsorption in order to prevent the removal of cells of the Chlorella microalgae strain from the treatment plant into the environment along with waste water.

After passing through the third filtering partition, the treated waters enter the fourth section of the treatment plant, where they are settled and further discharged into the water body.

The method is illustrated by the following examples. To evaluate the developed method, samples of quarry wastewater with a priority pollutant nitrate ion were used as model solutions for experiments. The hydrochemical characteristics of quarry wastewater are presented in Table 1.

Table 1 - hydrochemical composition of the model solution of quarry wastewater Pollutant concentration, mg/dm ³ pH NO ₃ ^2- _NH4 ⁺ NO ₂ ^{2- Cl-} Fe _total SO ₄ ^2- Ca2 ⁺ PO ₄ ^3- K ⁺ Na ⁺ 100-200.0 15.0 1.15 420 0.73 262 230 0.16 211.86 56 7-8

To study the removal efficiency of the priority pollutant, three models of wastewater treatment plants were built, one model for each type of vegetation. For each model, from 4 to 6 cylindrical cells, 25 cm high and 15 cm in diameter, were constructed from a plastic mesh. Each cell was filled with a load in the form of crushed stone and expanded clay with a fraction of 5–20 mm and 10–20 mm, respectively. To support plant growth, the nitrate ion was supplemented with a complex consisting of potassium and phosphate ions. In addition to the above models, a fourth tank with a nutrient solution of identical composition was used to monitor the background value of the nitrate ion.

Example #1. Conducting a laboratory experiment to determine the possibility of using species of higher aquatic vegetation for the purification of quarry wastewater from a priority pollutant (nitrate ion).

The experiment was carried out at a temperature of 20°C, a humidity of 68% and a pressure of 761 mm Hg. Simulation of the conditions for the treatment of quarry wastewater in the second section of the treatment plant was carried out. As treated quarry wastewater, a model solution with a hydrochemical composition according to Table 1 was used. Purification of a model solution of quarry wastewater was carried out in the models with vegetation described above.

The model solution of quarry wastewater entering the treatment enters the first section of the treatment plant, where impurities are deposited under the action of gravity within the length of the first section of the treatment plant and then passes through a filtering partition, where additional sedimentation of impurities occurs.

Further, the model solution of quarry wastewater enters the second section of the treatment plant for biological treatment, where plantings of broad-leaved cattail Typha latifolia L., common chastukha Alisma plantago-aquatica L. and jointed rush Juncus articulatus L. are located.

From the second section of the treatment plant, the model solution of quarry wastewater, passing through the filtering partition, enters the fourth section of the treatment plant, where it settles and is further discharged into a water body.

Sampling of the aqueous solution of each model was carried out twice a week with the measurement of the concentration of the nitrate ion on an LC-20 Shimadzu liquid chromatograph at the Ecosystem Research Center of St. Petersburg Mining University.

The results of the priority pollutant removal efficiency are shown in Table 2.

Table 2 - purification efficiency of the priority pollutant by higher aquatic vegetation Type of higher aquatic vegetation NO ₃ ^2- concentration, mg/dm ³ Cleaning efficiency, % Before cleaning After cleaning cattail broadleaf
Typha latifolia L. 100.0-200.0 55.0-110.0 45 Chastukha common
Alisma plantago-aquatica L. 100.0-200.0 65.0-130.0 35 Sitnik articulate
Juncus articulatus L. 100.0-200.0 65.0-130.0 35

Example #2. Carrying out a laboratory experiment to determine the possibility of using a species of lower aquatic vegetation for the purification of quarry wastewater from a priority pollutant (nitrate ion).

To study the efficiency of removal of the priority pollutant, 2 samples with a volume of 50 ml of the model solution were prepared. 5 ml of a Chlorella microalgae strain solution with an optical density of 1.967 was added to each sample. The determination of optical density was carried out on an IPS-03 suspension density meter.

The experiment was carried out at a temperature of 20°C, a humidity of 68% and a pressure of 761 mm Hg. Simulation of the conditions for the treatment of quarry wastewater in the third section of the treatment plant was carried out. As a treated quarry wastewater, a model solution with a hydrochemical composition according to Table 1 was used.

The model solution of quarry wastewater entering the treatment enters the first section of the treatment plant, where impurities are deposited under the action of gravity within the length of the first section of the treatment plant and then passes through a filtering partition, where additional sedimentation of impurities occurs.

From the first section of the treatment plant, the model solution of quarry wastewater, passing through the filtering partition, where the Chlorella microalgae cells are prevented from entering the second section, enters the third section of the treatment plant. The filter septum is a fine-mesh membrane with a pore size smaller than the cells of the microalgae Chlorella strain.

In the third section of the treatment plant, the introduction of lower aquatic vegetation - a strain of microalgae Chlorella is carried out.

Further, the model solution of quarry wastewater passes through a filtering partition, which is a fine-mesh membrane with a pore size smaller than the cell size of the introduced microalgae strain Chlorella , enters the fourth section of the treatment plant, where it settles and is further discharged.

Sampling of an aqueous solution of each model daily with measurement of the concentration of nitrate ion on a liquid chromatograph LC-20 Shimadzu at the Ecosystem Research Center of St. Petersburg Mining University.

The results of the priority pollutant removal efficiency are shown in Table 3.

Table 3 - purification efficiency of the priority pollutant of lower aquatic vegetation Type of lower aquatic vegetation NO ₃ ^2- concentration, mg/dm ³ Cleaning efficiency, % Before cleaning After cleaning Chlorella microalgae strain 100.0 57.5 40.3 200.0 57.3 71.8

Example #3. Conducting a laboratory experiment to determine the effectiveness of the joint use of higher and lower aquatic vegetation for the integrated treatment of quarry wastewater.

The experiment was carried out at a temperature of 20°C, a humidity of 68% and a pressure of 761 mm Hg. Simulation of the conditions for sequential treatment of quarry wastewater in the second and third sections of the treatment plant was carried out. Modeling of cleaning in the second section of the treatment plant was carried out according to example No. 1. Further, the purified model solution of quarry wastewater according to example No. 1 was used as the initial model solution of quarry wastewater for treatment in the third section. Modeling of cleaning in the third section of the treatment plant was carried out according to example No. 2.

The model solution of quarry wastewater entering the treatment enters the first section of the treatment plant, where impurities are deposited under the action of gravity within the length of the first section of the treatment plant and then passes through a filtering partition, where additional sedimentation of impurities occurs.

Further, the model solution of quarry wastewater enters the second section of the treatment plant for biological treatment, where plantings of broad-leaved cattail Typha latifolia L., common chastukha Alisma plantago-aquatica L. and jointed rush Juncus articulatus L. are located.

From the second section of the treatment plant, the model solution of quarry wastewater, passing through the filtering partition, where the Chlorella microalgae cells are prevented from entering the second section, enters the third section of the treatment plant. The filter septum is a fine-mesh membrane with a pore size smaller than the cells of the microalgae Chlorella strain.

In the third section of the treatment plant, the introduction of lower aquatic vegetation - a strain of microalgae Chlorella is carried out.

Further, the model solution of quarry wastewater passes through a filtering partition, which is a fine-mesh membrane with a pore size smaller than the cell size of the introduced microalgae strain Chlorella , enters the fourth section of the treatment plant, where it settles and is further discharged.

The effectiveness of phytoremediation was assessed by the concentration of pollutants in treated water after a 3-5-day period of residence of quarry wastewater in a model treatment plant. After this period, the concentration of substances was measured on the equipment of the Scientific Center "Ecosystem" of the St. Petersburg Mining University.

Table 4 - Efficiency of removing pollutants from quarry wastewater Pollutant concentration, mg/dm ³ NO ₃ ^2- _NH4 ⁺ NO ₂ ^{2- Cl-} Fe _total SO ₄ ^2- Ca2 ⁺ PO ₄ ^3- K ⁺ Na ⁺ in waste water 100-200.0 15.0 1.15 420 0.73 262 230 0.16 211.86 56 In purified water 25.0-30.0 1.3 0.1 190 0.25 175 200 0.05 200.26 43 MPC value ^* 45.0 1.5 3.0 350 0.3 500 - 3.50 - 200 Cleaning efficiency, % 75-85 91 91 55 66 33 13 69 55 23

^* According to SanPiN 1.2.3685-21 "Hygienic standards and requirements for ensuring the safety and (or) harmlessness of environmental factors for humans"

The results obtained, shown in table 4, indicate the effectiveness of this method, since the wastewater was purified from pollutants to the maximum permissible concentrations with a high degree of purification for the main pollutants.

The use of the claimed method allows for complex wastewater treatment from pollutants, the method provides an increase in the efficiency of wastewater treatment due to the implementation of preliminary mechanical purification from impurities using a filtration partition and the additive effect of higher and lower aquatic vegetation.

Claims (1)

A method for the biological treatment of quarry wastewater, including the supply of wastewater to a spatially separated cascade filter, made up of sections through which the treated water is sequentially supplied, microalgae are placed in one of the sections, and higher aquatic plants are placed in the other, characterized in that the treatment plant is divided by three filtering partitions into four sections, in the first section, mechanical cleaning of impurities and suspended solids is carried out due to the filtration partition, which is used as a fine-mesh membrane with a pore size of at least 10 microns, in the second section, higher aquatic vegetation is located - broad-leaved cattail Typha latifolia L., common chastukha Alisma plantago-aquatica L. and jointed rush Juncus articulatus L.; in the third section, the introduction of lower aquatic vegetation - microalgae Chlorella is carried out at the rate of 50 ml of quarry wastewater, 5 ml of a solution of Chlorella microalgae with an optical density of 1.967 is added; in the fourth section, sedimentation and further discharge into a water body take place; at the same time, fine-mesh membranes with a pore size of at least 8 μm are used as the second and third filtration partitions through which the treated wastewater passes from the second to the third section and from the third to the fourth section, while the period of stay of the quarry wastewater in the treatment plant is 3 -5 days.