The ceramic industry uses a lot of water in molds, final products and polishing, which results in a lot of dirty water that contains toxic chemicals and has a bad influence on the environment.
The highest levels of water pollution generated from washing molds and final products to eliminate any suspended contaminants on the pieces define ceramic industry effluents.
After the pouring stage, but before the drying stage, impurities are eliminated.
If used lubricant oil from garages and workshops is dumped into the sewage, it will produce oily effluent.
Tile polishing produces a considerable amount of wastewater with a high concentration of suspended solids and settable solids.
Method of wastewater Treatment of ceramic effluents
Industrial wastewater treatment from the ceramic manufacturing process mainly depends on physical and chemical treatment.
Physical treatment processes
Among the first treatment methods used were physical unit operations, in which physical forces are applied to remove contaminates.
Today they still form the basis of most process flow systems for wastewater treatment.
This section briefly discusses the most commonly used physical unit operations for ceramic effluent treatment.
Screening
The screening of wastewater, one of the oldest treatment methods, removes gross pollutants from the waste stream to protect downstream equipment from damage, avoid interference with plant operations and prevent objectionable floating material from entering the primary settling tanks.
Screening devices may consist of parallel bars, rods or wires, grating, wire mesh, or perforated plates, to intercept large floating or suspended material.
The openings may be of any shape but are generally circular or rectangular.
The material retained from the manual or mechanical cleaning of barracks and screens is referred to as “screenings”, and is either disposed of by burial or incineration or returned into the waste flow after grinding.
Flow Equalization
Flow equalization is a technique used to improve the effectiveness of secondary and advanced wastewater treatment processes by leveling out operation parameters such as flow, pollutant levels and temperature over some time.
Variations are damped until a near-constant flow rate is achieved, minimizing the downstream effects of these parameters.
Flow equalization may be applied at several locations within a wastewater treatment plant, e.g., near the head end of the treatment works, before discharge into a water body and before advanced waste treatment operations.
Sedimentation
The gravity settling of heavy particles floating in a mixture is a fundamental and commonly utilized unit operation in wastewater treatment.
This technique is utilized in the primary settling basin to remove grit and particle matter, in the activated sludge settling basin to remove biological floc, and in the chemical coagulation process to remove chemical flow.
Sedimentation occurs in a settling tank, also known as a clarifier.
The three main designs are horizontal flow, solids contact and inclined surface.
It is critical to remember when building a sedimentation basin that the system must produce both cleared effluent and concentrated sludge.
Four types of settling occur, depending on particle concentration: discrete, flocculent, hindered and compression.
It is common for more than one type of settling to occur during a sedimentation operation.
Sand filtration
The filtration of effluents from wastewater treatment processes is a relatively recent practice but has come to be widely used for the supplemental removal of suspended solids from wastewater effluents of biological and chemical treatment processes, in addition to the removal of chemically precipitated phosphorus.
The entire filtration procedure is divided into two stages: filtration and cleaning or backwashing.
The filtered wastewater is passed through a filter bed made of granular material (sand, anthracite, and/or garnet), with or without chemicals added.
Within the filter bed, suspended solids contained in the wastewater are removed using a complex process involving one or more removal mechanisms such as straining, interception, impaction, sedimentation, flocculation and adsorption.
The phenomena that occur during the filtration phase are the same for all types of filters used for wastewater filtration.
The cleaning/backwashing phase differs, depending on whether the filter operation is continuous or semi-continuous.
The filtering and cleaning processes in semi-continuous filtration occur sequentially, whereas the filtering and cleaning procedures in continuous filtration occur concurrently.
Chemical treatment processes
Chemical processes used in wastewater treatment are designed to bring about some form of change using chemical reactions.
They are always used in conjunction with physical unit operations and biological processes.
In general, chemical unit processes have an inherent disadvantage compared to physical operations in that they are additive processes.
That is, the dissolved elements of the wastewater are often increased.
If the wastewater is to be reused, this can be a major factor.
This section covers the fundamental chemical unit processes that are used for ceramic effluent treatment, such as chemical precipitation, adsorption, disinfection, dichlorination and other uses.
Chemical precipitation
Chemical coagulation of raw wastewater before sedimentation promotes the flocculation of finely divided solids into more readily settleable flocs, thereby enhancing the efficiency of suspended solids, BOD5 and phosphorus removal as compared to plain sedimentation without coagulation.
The degree of clarification obtained depends on the number of chemicals used and the care with which the process is controlled.
The selection of coagulants for enhanced sedimentation is based on performance, dependability and cost.
To establish doses and effectiveness, performance evaluation employs jar testing of actual wastewater.
Chemical coagulants that are commonly used in wastewater treatment include alum (Al2(SO4)3.14.3H2O), ferric chloride (FeCl3.6H2O), ferric sulfate (Fe2(SO4)3), ferrous sulfate (FeSO4.7H2O) and lime (Ca (OH)2).
Organic polyelectrolyte is sometimes used as a flocculation aid.
Suspended solids removal through chemical treatment involves a series of three-unit operations: rapid mixing, flocculation and settling.
First, the chemical is added and completely dispersed throughout the wastewater by rapid mixing for 20-30 seconds in a basin with a turbine mixer.
By mechanically creating velocity gradients within the liquid, coagulated particles are brought together by flocculation.
In a basin with turbine or paddle-type mixers, flocculation takes 15 to 30 minutes.
Coagulation has several advantages, including increased removal efficiency, the ability to use higher overflow rates and more constant performance.
Coagulation, on the other hand, produces a bigger mass of primary sludge that is frequently more difficult to thicken and dewater.
It also has higher operational costs and necessitates more attention from the operator.
Disinfection
Disinfection refers to the selective destruction of disease-causing microorganisms.
This process is of importance in wastewater owing to the nature of wastewater, which harbors several human enteric organisms that are associated with various waterborne diseases.
Commonly used means of disinfection include the following:
1- Physical agents such as heat and light;
2- Mechanical means such as screening, sedimentation, filtration, and so on;
3-Radiation, mainly gamma rays;
4- Chemical agents including chlorine and its compounds, bromine, iodine, ozone, phenol, and phenolic compounds, alcohols, heavy metals, dyes, soaps, synthetic detergents, quaternary ammonium compounds, hydrogen peroxide and various alkalis and acids.
The most common chemical disinfectants are oxidizing chemicals; chlorine is the most widely used.
Disinfectants act through one or more of several mechanisms, including damaging the cell wall, altering cell permeability, altering the colloidal nature of the protoplasm, and inhibiting enzyme activity.
In applying disinfecting agents, several factors need to be considered: contact time, concentration and type of chemical agent, intensity and nature of the physical agent, temperature, number of organisms and nature of suspending liquid.
References
[1] Egyptian Environmental Affairs Agency (EEAA); Egyptian Pollution Abatement Project (EPAP) Inspection Manual of Ceramic Industry, 2003.
[2] Economic and Social Commission for Western Asia, “Wastewater Treatment Technologies a General Review “, United Nations, 11 September 2003.
[3] Metcalf and Eddy, Inc. Wastewater Engineering: Treatment Disposal and Reuse, third edition. New York: McGraw-Hill, 1991.
[4] Metcalf and Eddy, Inc. Wastewater Engineering: Treatment and Reuse, fourth edition. New York: McGraw-Hill, 2003.
[5] Qasim, S.R., Wastewater Treatment Plants: Planning, Design, and Operation (Lancaster, Pennsylvania: Technomic Publishing Company, 1999).
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