Nature is constantly evolving, wise,unique, self-healing organism. However, for such a recovery should take a certain amount of time. Under the conditions of constant anthropogenic attack, nature lacks the strength and resources to restore itself. This causes global environmental problems. One of them is pollution of the World Ocean and, as a result, the lack of clean drinking water in many regions of the world. Due to pollution of water bodies, their inhabitants are also affected. This article will discuss the wastewater of industrial enterprises, methods of their valuation and purification.
Environmental problems of big cities
It's hard to imagine a city that does not renderenvironmental impact. The first and most important thing to do in order to establish a settlement is the alienation of a large territory and its transformation from a forest or field into reinforced concrete jungle. This is not all. The products of human activity pollute the nature and often cause irreparable damage to the animal and plant world.
Among the main environmental problems of industrial cities are:
- pollution of rivers, seas and lakes as a result of discharges of wastewater from industrial enterprises containing toxic pollutants;
- air pollution due to emissions from enterprises;
- contamination of soil, water bodies and air (odor) with hazardous industrial waste;
- the destruction of green spaces and their inhabitants;
- lack of clean drinking water;
- climate change and ozone depletion.
Все данные процессы происходят под действием anthropogenic factor, and therefore it is in the forces of man to change the situation for the better. Wastewater from industrial enterprises and their treatment should be a priority for the internal policies of cities and the support of enterprises engaged in this type of activity.
Types of wastewater
In this case, the classification is based on the chemical composition in order to select recycling methods. Sewage of industrial enterprises are divided into three types:
- domestic wastewater;
- industrial effluents;
- surface and infiltration drains.
Domestic wastewater
This type of discharge is typical for any building andfacilities equipped with a bathroom, and therefore the composition of such discharges, as a rule, is always the same. Domestic wastewaters are characterized by a high content of organic matter, the presence of nitrogen, phosphorus and coarse impurities. Cleaning of this type of pollution, as a rule, biological and does not cause difficulties, high energy consumption, and therefore is performed by the utilities of municipal services.
Состав сточных вод промышленных предприятий This type differs only in that workers can drain into the toilet and sink fluids that can not be drained there. This is very typical for laboratories, chemical plants, electroplating plants, pharmaceutical plants.
Surface wastewater
Все выпадающие в городах осадки по системе Storm sewage flow into storage tanks, and then to the treatment plant. This type of wastewater, in fact, is polluted only by suspended solids and oil products, and therefore all urban rainwater are cleaned according to the principle of sedimentation and removal of oil products.
It is important to understand that data is being collected.from the roof, asphalt pavement and even drains from the soil and grass. The main difference between wastewaters of industrial enterprises of this type is that with unfair gas cleaning and spills (accidents) they can be contaminated with specific substances characteristic of this type of production. Therefore, this type of discharge must be pre-cleaned.
Industrial wastewater
Не бывает полностью безотходных технологий.Even the smallest enterprise that uses water in its production process forms wastewater. The nature of the pollution of such discharges varies from plant industry.
- Целлюлозно-бумажная промышленность отличается very polluted drains. Therefore, cleaning in this case is assumed to be multistage and high-quality. The main pollutants are fiber, selenium, chlorine, turpentine, SO2.
- Motor transport enterprises form wastewater during washing, painting, repair, and therefore they are heavily polluted with oil products, phenols, suspended solids.
- Oil refineries use systemsrecycling water supply. Sewage waters of some industrial enterprises contain hardness salts, petroleum products, sulphates, suspended solids, chlorides.
- Poultry farms and meat processing plants form discharges that pollute water bodies and sewage systems with nitrogen, phosphorus, potassium, viruses and bacteria.
Environmental Regulation System
To avoid accidents and negative consequences,It is necessary to exercise control over any industry. In order to protect the environment, wastewater treatment of industrial enterprises and methods for their valuation are laid down in the environmental environmental legislation of the Russian Federation. It is based on the principles of the rational use of natural resources, on the right of every person to a healthy environment and on the principle of sustainable development.
The basis for environmental regulation isthe concept of maximum permissible concentration (MPC), as well as maximum permissible emissions (MPE) and discharges (MPD). Such regulation allows setting maximum values for pollutants that can be discharged into a reservoir or sewage system. It is important to understand that the MPC for discharge into the reservoir will be much stricter than the MPC for discharge into the city sewer, as in the latter case, the wastewater will first be accumulated and cleaned at municipal sewage treatment plants, and then only flow into the reservoir.
Правовое регулирование в области охраны водных resources is based on the Federal Law 416-ФЗ "On water supply and sanitation" dated November 29, 2011, regulations and GOSTs, SP, SanPiNs. In the latter, the allowable concentrations are given and specific recommendations are given.
SanPiN for MPC industrial wastewaterenterprises of the Russian Federation establishes standards for the qualitative composition of wastewater for discharge into water bodies and requirements for sanitary protection of wastewater. This document is practical, and therefore it normalizes impurities, color, temperature, pH, salinity, BOD5, infectious agents. Sanitary rules and norms 2.1.5.980-00 "Wastewater disposal of populated areas, sanitary protection of water bodies. Hygienic requirements for the protection of surface water" adopted 01.01.2001. They are based on the principles of resource conservation, that is, do not allow discharges, if there is a possibility of reuse of water with pre-treatment.
If we are talking about specific MACs for pollutingsubstances, then SanPiN for wastewater of industrial enterprises is not valid here. For such cases, Government Resolution No. 644 adopted on July 29, 2013, sets out the basic principles for using sewerage systems. The document developed a list of substances prohibited for discharge, as well as the MPC for wastewater from industrial enterprises for discharge into the sewage system. If we are talking about common and domestic sewage systems, the concentration of certain pollutants should not exceed the following marks (mg / dm3):
- suspended solids ≤ 300;
- sulfides ≤ 1.5;
- sulphates ≤ 1000;
- chlorides ≤ 1000;
- total phosphorus ≤ 12;
- total nitrogen ≤ 50;
- petroleum products ≤ 10;
- chloramines and chlorine ≤ 5;
- phenols (total) ≤ 5;
- iron and aluminum ≤ 5;
- zinc, copper, manganese ≤ 1;
- hexavalent chromium ≤ 0.05;
- lead, nickel ≤ 0,25;
- cadmium ≤ 0.015;
- arsenic ≤ 0.05;
- mercury ≤ 0,005;
- Synthetic surfactants (non-ionic, anionic) ≤ 10;
- volatile organic compounds ≤ 20;
- fats ≤ 50.
In this case, the temperature of the wastewater should not exceed + 40 ° C. If we are talking about discharges into stormwater drainage systems, the MPC of some substances become noticeably stricter:
- sulphates ≤ 500;
- petroleum products ≤ 8.
Cleaning methods
Техника и технология сточных вод – довольно extensive and constantly developing discipline. The basis of all cleaning methods is the separation and release of impurities in the solid phase and the formation of pure water. To do this, there are the following methods:
- upholding;
- mechanical filtration;
- physico-chemical (flotation, flocculation, coagulation, reagent treatment);
- sorption;
- reverse osmosis and ultrafiltration;
- disinfection (UV, ozonation, chlorination).
It is important to understand that all these methods are used.not separately, but in a complex. The classical technological scheme includes sedimentation, mechanical filtration, physico-chemical method, sorption and disinfection. Each of them will be briefly described below.
Upholding
Essentially important and the first stage of cleaningWastewater from industrial enterprises is upholding (clarification). At this stage, equipment is used, called settling pits. They are a reinforced concrete (sometimes fiberglass) tank, with a slight inclination of the bottom towards the pit. At this stage, the water is literally settled (stays in the sump) for at least 3 days. During this time, all undissolved impurities are released: heavy suspended solids settle to the bottom and slide into the pit, and oil products float to the top and are removed with a special device (skimmer) or mechanical scraper.
This cleaning step is really the most importantsince all further equipment will not be able to work if coarse impurities (sand, rust), which are trapped in the sump, fall into it.
Physico-chemical methods
Industrial wastewater treatment technologiesenterprises always provide for the main processing module, on which the release of substances dissolved in water takes place and their transformation into insoluble form. As it usually serves a physico-chemical method of wastewater treatment. This is done in flotation cells and coagulators.
Flotators
To highlight insoluble substances in the dataunits use air bubbles. Flotators are tanks in which water accumulates, and a mixture of water and air is supplied from the bottom with a special device for bubbling. Air bubbles capture pollutants due to their stickiness and carry them up to form a foam called flotation sludge. Obviously, this method is suitable for light dissolved impurities. Coagulants can be added here, which enlarge the particles of pollutants, if they are very small. The dose of reagents is selected in an optimal way so that they do not destroy the air bubble.
Coagulators
To highlight insoluble substances in the dataThe units use the principles of adhesion and coagulation, that is, sticking and coarsening of impurities. A coagulator (or electrocoagulator) is a container with coalescent partitions into which a coagulant-flocculant is fed in order to enlarge the impurities. Heavy particles of pollutants eventually settle to the conical bottom and are removed. Reagents are not added to the electrocoagulator, their action is replaced by aluminum or iron electrodes.
These methods provide the maximum cleaning effect and are used in almost all sewage treatment plants.
Filtration
This cleaning method is used to trap residual impurities in water. Filtration is conventionally divided into two types: mechanical and sorption.
The mechanical filter is a tank,gravel-loaded or filter cloth. In this case, the mechanical cleaning of the impurities takes place and they are retained in the pores of the material. At this time, water flows through the pores and is cleaned.
Sorption filter is filled with activatedcoal, silica gel, schungite and any other sorbent, which absorbs the pollution. This download is either completely changed or washed and used again.
Disinfection
This cleaning method is set at the endeach technological scheme. Disinfection is carried out using ultraviolet lamps, hypochlorite or ozonator installation. This type of cleaning is necessary to remove residual viruses and bacteria in industrial wastewater.
Cleaning "at the beginning of the pipe"
The main principle of ecology lies inpreventiveness and says that if pollution can be prevented, the accident is not allowed, and the resource is reused, then the nature user is obliged to do so. Cleaning "at the beginning of the pipe" regarding wastewater involves the following set of measures:
- circulating and closed water supply systems with water reuse for economic needs;
- compilation of water balance and water footprint, showing the specific consumption of water, in order to reduce them whenever possible;
- studying advanced wastewater treatment methods;
- establishment of industrial equipment in order to reduce water consumption.
Today, the problem of providing the population with clean water is one of the priorities of the policies of many countries. Water is the source of life.
