RU2569533C1 - Reagentless method of treatment and decontamination of sewage sludge - Google Patents

Abstract

FIELD: ecology.

SUBSTANCE: method comprises sludge treatment with super-high-frequency electromagnetic radiation. The mixture of sewage sludge, which is a primary sludge and excess activated sludge in the ratio of 1:2 is treated in a microwave oven having the metal walls. The radiation power is 800-1000 W, the duration of sludge treatment is 5-10 minutes, the frequency of radiation is 3.109-3.1010 Hz.

EFFECT: reduction of content of heavy metals in sludge, reduction of volume, moisture content reduction, increase in the speed of sedimentation and filtration, disinfection, reduction of stickiness, absence of the sludge putrescibility.

6 dwg, 1 tbl

Description

The invention relates to methods for the treatment and disposal of wastewater sludge generated in urban wastewater treatment plants (GOSK).

Wastewater sludge (WWS) is a suspension released from wastewater in the process of mechanical, biological and physico-chemical treatment. The main types of sediments at GSCC are the primary sediment trapped by the primary sedimentation tanks, and excess activated sludge from the secondary sedimentation tanks. The spatial structure of sediments is a colloidal system in which the dispersed phase consists of solid particles of organic and mineral origin, and the dispersed medium is water with substances dissolved in it. Poor rainfall loss, heavy metal content, as well as contamination with pathogenic bacteria makes it difficult for their subsequent processing and disposal.

The main ways to improve the properties of WWS are the use of chemical reagents (coagulants and flocculants) and subsequent mechanical dehydration, for example, RF patent 2484024. Most reagents are toxic and serve as sources of secondary pollution of sewage sludge.

It is possible to influence the properties of precipitation not only with chemical reagents, but also with physical fields, for example, a microwave electromagnetic field (microwave electromagnetic field). The biophysical effect of electromagnetic radiation is associated with the ionization of molecules of a substance and the formation of exciting particles that interact with each other and other molecules or decay with the formation of free radicals [Ismailov E.Sh. Biophysical action of microwave radiation. M., 1987, p. 5]. These processes cause oxidation and decomposition of substances, structural changes and a decrease in the activity of enzymes of microorganism cells. The bactericidal effect of electromagnetic radiation is known [Classen V.I. Magnetization of water systems. M .: Chemistry, 1978, p. 87; Ismailov E.Sh. Biophysical action of microwave radiation. M., 1987, p. 86].

A known method of disinfecting industrial wastewater in a pulsed electromagnetic device with a magnetic field of 70-80 kA / m and a frequency of 2-10 imp./s [RU 2123477 C1, publ. 1996].

A known method of disinfecting a flow of a liquid medium with at least one constant magnetic field. The flow velocity is set equal to 0.1-10 m / s, and a constant magnetic field is created with a magnetic induction vector directed perpendicular to the fluid flow and having a value greater than 0.02 T [RU 2126772 C1, IPC C02F 1/48, publ. 1998].

A known method of antibacterial treatment of a fluid flow by exposing the swirling fluid flow to magnetic and electric fields and creating an ion concentration gradient [RU 2376247 C2, IPC C02F 1/48, publ. 2006].

Known is a comprehensive method of reagent-free wastewater treatment and briquetting, including disinfecting briquettes of settled sludge in microwave ovens [RU 2431610 C2, IPC C02F 9/12, publ. 10/20/2011].

The disadvantages of the above methods are in some cases low efficiency, the narrow application of electromagnetic radiation is only a bactericidal effect at the final stage of wastewater treatment.

The objective of the invention is the creation of a non-reagent method for the treatment of WWS having a multifactorial effect (improving a number of properties of precipitation), having high efficiency, cost-effective and easy to implement.

The technical effect is the improvement of the basic properties of precipitation: a decrease in the content of heavy metals, a decrease in sediment volume, a decrease in humidity, an increase in the rate of sedimentation and filtration, disinfection, a decrease in stickiness, and the absence of decay.

The specified technical result is achieved by the fact that in the non-reagent processing method, the precipitation mixture, which is the primary precipitate and excess activated sludge in a ratio of 1: 2, is subjected to microwave radiation (UHF EMP) with a radiation power of 800-1000 W, radiation frequency 3 * 10 ⁹ -3 * 10 ¹⁰ Hz, the processing time is 5-10 minutes

It has been experimentally proved that the electromagnetic radiation power and processing time depend on the volume of the processed sludge. So for a volume of 500 ml, the optimal power is up to 1000 watts and a duration of 5-10 minutes. An increase in the power of the microwave generator and the processing time lead to a deterioration of some properties of the precipitation (for example, when microwave processing for more than 10 minutes, the content of valuable organic substances of potassium and phosphorus decreases), as well as to an increase in energy consumption.

The technical solution is illustrated by illustrative materials, where in FIG. 1 shows the dependence of the decrease in the volume of the WWS mixture during sedimentation on the duration of the microwave EM treatment; in FIG. 2 - dependence of the decrease in humidity of the precipitation mixture on the power of the microwave EM processing; in FIG. 3 - graphs comparing the rate of filtration of a mixture of sediments; in FIG. 4 shows the adhesion of the initial sewage sludge; in FIG. 5 - adhesion of the precipitate after microwave processing; in FIG. 6 shows the rotability of a mixture of sediments.

The method is as follows.

Microwave treatment is subjected to a mixture of precipitation - primary sediment and excess activated sludge (1: 2) from the existing sewage treatment plant in Tyumen before the reagent is introduced. A mixture of precipitates with a volume of 300-500 ml is placed in a microwave oven having metal walls. When you turn on the microwave oven, the magnetron generates electromagnetic radiation with a wave range of 10 ^-1 -10 ^-2 m and a frequency of 3 * 10 ⁹ -3 * 10 ¹⁰ Hz. The processing time is 5-10 minutes.

As a result of the implementation of the method according to the claimed technical solution, the following results were obtained:

- a significant (25-35%) decrease in sediment volume during sedimentation (Fig. 1);

- decrease in humidity (from 94.5% to 91.15%) (Fig. 2);

- an increase in the filtration rate (1.2 times) (Fig. 3);

- reduction of stickiness (Fig. 4, 5);

- lack of rotability of the sewage sludge (the sludge was settled in laboratory cylinders for 1 day) (Fig. 6);

- an increase in the content of heavy metals in the centrate (centrate is the liquid phase after sedimentation of the sewage sludge washed with distilled water). Key indicators are shown in table 1;

- sediment sterilization - there is a conclusion on conducting a parasitological study at the testing laboratory center of the Federal State Health Institution “Center for Hygiene and Epidemiology in the Tyumen Region”. Defined indicators: lamblia cysts (Giardia intestinalis), eggs and helminth larvae. Research results: in the sample of the precipitation mixture after treatment with microwave radiation, these types of pathogenic microorganisms were not found.

Table 1 The content of heavy metals in the centrate No. p / p Name of indicator The content of the indicator (dry. Substance) centrate without treatment, mg / kg The content of the indicator (on dry matter) is a centrate with microwave EM processing, mg / kg one Mercury 0.145 0.146 2 Lead 35.42 41,99 3 Zinc 145.00 151.00 four Nickel 19.43 20.68 5 Chromium 25.21 29.75

The proposed method allows without the use of reagents to improve a number of properties of the WWS, significantly reduce processing time. For example, microwave treatment of the sediment for 10 minutes leads to the death of all known pathogenic bacteria, and for complete disinfection of WWS in silt fields, 3-4 years are required. As a result of the use of microwave EMP, a safe product is obtained for reuse, for example, as fertilizer in agriculture, for soil restoration, production of building materials, road construction, etc.

A distinctive feature of the claimed method is that it has been shown for the first time that microwave electromagnetic radiation can be used to improve a number of wastewater sludge properties — increasing the speed of processing processes, reducing the content of heavy metals, decreasing humidity, etc. The simplicity of the equipment used makes it possible to obtain a universal and relatively inexpensive method of processing precipitation.

Comparative economic calculations to justify the use of microwave EMP in the treatment of sewage sludge show that the cost of dewatering sewage sludge from microwave radiation is 1.5 times lower than the cost of using the flocculant used today at Tyumen State Mining and Processing Plant.

Claims (1)

The method of non-reagent treatment and disposal of sewage sludge, which consists in processing a mixture of sludge, which is the primary sludge and excess activated sludge in a ratio of 1: 2, microwave radiation at a radiation power of 800-1000 W, radiation frequency 3 * 10 ⁹ -3 * 10 ¹⁰ Hz and a duration of 5-10 minutes

Images