Wastewater from industrial enterprises and methods for their regulation

2024 Author: Howard Calhoun | [email protected]. Last modified: 2024-01-02 13:48

Nature is a constantly evolving, wise, unique, self-healing organism. However, for such a recovery, a certain amount of time must pass. In the conditions of constant anthropogenic attack, nature does not have enough strength and resources to restore itself. Because of this, global environmental problems arise. One of them is the pollution of the oceans and, as a result, the lack of clean drinking water in many regions of the world. Due to the pollution of water bodies, their inhabitants also suffer. This article will focus on the wastewater of industrial enterprises, methods for their rationing and purification.

Environmental problems of big cities

It is hard to imagine a city that does not have an impact on the natural environment. The first and main thingwhat needs to be done in order to establish a settlement is the alienation of a large territory and its transformation from a forest or a field into a reinforced concrete jungle. It doesn't end there. Human waste products pollute 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 due to industrial wastewater discharges containing toxic pollutants;
• air pollution from industrial emissions;
• soil, water and air pollution (smell) with hazardous industrial waste;
• destruction of green spaces and their inhabitants;
• lack of clean drinking water;
• climate change and ozone depletion.

All these processes occur under the influence of the anthropogenic factor, and therefore it is in the power of man to change the situation for the better. Wastewater from industrial enterprises and their treatment should become a priority for the internal policy of cities and support for 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 disposal methods. Industrial wastewater is divided into three types:

• household waste;
• industrial waste;
• surface and infiltration runoff.

For each typedischarges normally have their own sewer system, although sometimes in some cities they still mix everything together. This only exacerbates the problem of subsequent cleaning.

Household wastewater

This type of discharge is typical for any building and structure equipped with a bathroom, and therefore the composition of such discharges, as a rule, is always the same. Domestic wastewater is 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, is biological and does not cause difficulties, high energy costs, and therefore is carried out by the utilities systems.

The composition of wastewater from industrial enterprises of this type differs only in that workers can pour liquids into the toilet and sink that cannot be drained there. This is very common in laboratories, chemical plants, electroplating plants, pharmaceutical plants.

Surface waste water

All rainfall that falls in cities through the storm sewer system enters storage tanks, and then to wastewater treatment plants. This type of wastewater, in fact, is polluted only with suspended solids and oil products, and therefore all city storm drains are cleaned according to the principle of settling and removing oil products.

It is important to understand here that these emissions are collected from the roof, asph alt pavement, and even runoff from soil and grass is taken into account. The main difference between wastewater from industrial enterprises of this typein the fact that in case of unscrupulous 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

There are no completely waste-free technologies. Even the smallest enterprise that uses water in its production process generates wastewater. The nature of the pollution of such discharges varies from plant industry.

• The pulp and paper industry is characterized by very polluted effluents. Therefore, cleaning in this case is assumed to be multi-stage and high-quality. The main pollutants are fibers, selenium, chlorine, turpentine, SO_2.
• Motor transport enterprises generate wastewater during washing, painting, repair, and therefore they are heavily polluted with oil products, phenols, suspended solids.
• Refineries use water recycling systems. Wastewater of some industrial enterprises contains hardness s alts, oil products, sulfates, suspended solids, chlorides.
• Poultry farms and meat processing plants generate discharges that pollute water bodies and sewage systems with nitrogen, phosphorus, potassium, viruses and bacteria.

As can be seen from the list, wastewater treatment of industrial enterprises strictly depends on the scope of the plant and the composition of pollutants.

Environmental regulation system

Toto avoid accidents and negative consequences, it is necessary to exercise control over any industry. In order to protect the environment, the treatment of wastewater from industrial enterprises and the methods for their regulation are laid down in the environmental legislation of the Russian Federation. It is based on the principles of rational use of natural resources, on the right of every person to a he althy environment and on the principle of sustainable development.

The basis for environmental regulation is the concept of maximum allowable concentration (MPC), as well as maximum allowable emissions (MPE) and discharges (MPD). This regulation makes it possible to set maximum values for pollutants that can be discharged into a water body or sewerage system. At the same time, it is important to understand that the MPC for discharge into a reservoir will be much stricter than the MPC for discharge into a city sewer, since in the latter case, wastewater will first be accumulated and treated at municipal sewage treatment plants, and then only enter the reservoir.

Legal regulation in the field of water resources protection is based on the Federal Law 416-FZ "On water supply and sanitation" dated November 29, 2011, by-laws and GOSTs, SP, SanPiNs. The latter lists allowable concentrations and makes specific recommendations.

SanPiN for the MPC of wastewater from industrial enterprises of the Russian Federation establishes standards for the qualitative composition of wastewater for discharge into water bodies and requirements for the sanitary protection of wastewater. This document is practical in nature, and thereforeimpurities, color, temperature, pH, mineralization, BOD5, infectious agents are normalized in it. Sanitary rules and norms 2.1.5.980-00 "Water disposal of populated areas, sanitary protection of water bodies. Hygienic requirements for the protection of surface waters" were adopted on 01.01.2001. They are based on the principles of resource conservation, that is, they do not allow discharges if it is possible to reuse water with preliminary purification.

If we are talking about specific MPCs for pollutants, then SanPiN for wastewater from industrial enterprises is not valid here. For such cases, the Decree of the Government No. 644 adopted on July 29, 2013, which sets out the basic principles for using sewerage systems, applies. The document developed a list of substances prohibited for discharge, as well as the MPCs for wastewater from industrial enterprises for discharge into the sewer. If we are talking about general alloy and domestic sewage systems, then the concentration of some 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;
• STS (nonionic, anionic) ≦10;
• VOC ≦ 20;
• fats ≦ 50.

In this case, the wastewater temperature should not exceed +40°С. When it comes to discharges into storm sewer systems, the MPCs for some substances become noticeably stricter:

• sulphates ≦ 500;
• petroleum products ≦ 8.

Cleaning methods

Wastewater engineering and technology is a fairly broad and constantly evolving discipline. The basis of all cleaning methods is the separation and separation of contaminants into the solid phase and the formation of clean water. There are the following ways to do this:

• defending;
• mechanical filtration;
• physical and 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 not used separately, but in combination. The classical technological scheme includes settling, mechanical filtration, physical and chemical method, sorption and disinfection. Each of them will be briefly described below.

Settling

The fundamentally important and first stage of industrial wastewater treatment is settling (clarification). At this stage, equipment called settling tanks is used. They are a reinforced concrete (sometimes fiberglass) tank, with a slight slope of the bottom towards the pit. At this stage, the waterliterally settles (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, while oil products float to the top and are removed by a special device (skimmer) or mechanical scraper.

This cleaning stage is really the most important, since all further equipment will not be able to work if coarse impurities (sand, rust) get into it and linger in the sump.

Physico-chemical methods

Wastewater treatment technologies of industrial enterprises always provide for the main processing module, which separates the substances dissolved in water and converts them into an insoluble form. It is usually used as a physico-chemical method of wastewater treatment. This is done in flotators and coagulators.

Scatters

To isolate insoluble substances, air bubbles are used in these aggregates. Floaters are containers in which water accumulates, and a mixture of water and air is supplied from below by a special bubbling device. Air bubbles trap contaminants due to their stickiness and carry them to the top, forming a foam called flotation sludge. Obviously, this method is suitable for light dissolved impurities. Coagulants can also be added here, which enlarge the particles of pollutants, if they are very small. The dose of reagents is selected optimally,so they don't destroy the air bubble.

Coagulators

To isolate insoluble substances, these aggregates use the principles of adhesion and coagulation, that is, adhesion and coarsening of impurities. A coagulator (or electrocoagulator) is a container with coalescent partitions, into which a coagulant-flocculant is fed in order to coarsen impurities. Heavy particles of contaminants eventually settle into 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 wastewater treatment plants.

Filtering

This cleaning method is used to trap residual impurities in the water. Filtration is conditionally divided into two types: mechanical and sorption.

Mechanical filter is a container filled with gravel or filter cloth. In this case, mechanical cleaning of contaminants and their retention in the pores of the material takes place. At this time, water flows through the pores and is purified.

The sorption filter is filled with activated carbon, silica gel, shungite and any other sorbent that seems to absorb impurities. This load is either changed completely or washed and used again.

Decontamination

This cleaning method is installed at the end of each flow chart. Disinfection is carried out using ultraviolet lamps,hypochlorite or ozone unit. This type of treatment is necessary to remove residual viruses and bacteria in industrial wastewater.

Cleaning "at the beginning of the pipe"

The main principle of ecology is prevention and says that if pollution can be prevented, an accident can be prevented, and the resource is reused, then the nature user is obliged to do this. Cleaning "at the beginning of the pipe" regarding wastewater involves the following set of measures:

• circulating and closed water supply systems with reuse of water for household needs;
• compilation of the water balance and water footprint, showing the specific water discharge, in order to reduce them as much as possible;
• learning best practices for wastewater treatment;
• improvement of industrial equipment to reduce water consumption.

Today the problem of providing the population with clean water is one of the priorities of the policy of many countries. Water is the source of life.