What is an Effluent Treatment Plant (ETP) and its Role in Distillery, Electroplating, Pharmaceutical, Pulp & Paper Industries?
What is an effluent treatment plant (ETP) :
Water as we all know is a crucial element for life and it cannot be wasted. Industrial wastewater treatment covers the mechanisms and processes used to treat wastewater that is produced as a by-product of industrial or commercial activities and produces a liquid effluent suitable for circulation into the process areas.
ETP stands for Effluent Treatment Plant. It is a system that removes toxic and non-toxic material from water and making it usable for various purposes. An ETP is a plant where the treatment of industrial effluents and waste waters is done. The ETP plants are used widely in industrial sector, for example, pharmaceutical industry, to remove the effluents from the bulk drugs.
Source of Industrial Wastewater:-
Wastewater generated from agricultural and food operations is biodegradable and non-toxic, but has high concentrations of biochemical oxygen demand (BOD) and suspended solids. Vegetable washing generates waters with high loads of particulate matter and some dissolved organic matter.
Effluent from the pulp and paper industry is generally high in suspended solids and BOD. Plants that bleach wood pulp for paper making may generate chloroform, dioxins, furans, phenols and chemical oxygen demand (COD). Increased BOD or COD loadings, as well as organic pollutants, may require biological treatment such as activated sludge or up flow anaerobic sludge blanket reactors. For mills with high inorganic loadings like salt, tertiary treatments may be required, either general membrane treatments like ultrafiltration or reverse osmosis.
Waste waters can be contaminated by feedstock materials, by-products, product material in soluble or particulate form. Treatment facilities that do not need control of their effluent typically opt for a type of aerobic treatment, i.e. aerated lagoons.
The production of iron from its ores involves powerful reduction reactions in blast furnaces. Cooling waters are inevitably contaminated with products especially ammonia and cyanide. Contamination of waste streams includes gasification products such as benzene, naphthalene, anthracene, cyanide, ammonia, phenols, cresols together with a range of polycyclic aromatic hydrocarbons.
Power plants are a major source of industrial wastewater. Many of these plants discharge wastewater with significant levels of metals such as lead, mercury, cadmium and chromium as well as arsenic, selenium and nitrogen compounds.
Need Of ETP:
Water is basic necessity of life used for many purposes, one of which is Industrial use. Industries generally pay heavy taxes for the raw water. But water once get used gets contaminated so it should be well treated so it can satisfy the proper prerequisites of usage in the plant. Thus an effluent treatment plant is always laid down in any industrial plant.
ETP Plant Uses/Applications in Different Industries:
1. Effluent Treatment Plant (Zero Liquid Discharge) for Distillery Industries:
The Distillery industries utilize molasses and different grains as raw materials.
- Molasses based Distillery Industry: In India bulk of the alcohol is being produced from sugar cane molasses. Molasses is a thick viscous byproduct of the sugar industry which is acidic in nature, rich in salts, dark brown in colour and it also contains sugar which could not be crystallized. For manufacturing alcohol, the Molasses is diluted with water into a solution containing 15-16 % of sugars. This solution is then inoculated with yeast strain and is allowed to ferment at room temperature. The fermented wash is distilled in a series of distillation columns to obtain alcohol of adequate/ requisite strength and quality/specification.
- Grain-based Distillery Industry: There are two main distillery processes, dry-milling distillery and wet-milling distillery.
The dry-milling (or dry-grind) process is the main process for producing ethanol. This process starts with grinding before steeping the grain in water and results in ethanol and various by-products.
In the wet-milling process, the grains are steeped and the kernels are separated into various fractions, which allows for the production of multiple food and industrial products including starch, proteins, fructose, oil and ethanol.
Distilleries have been generating huge quantities of high toxic effluents. The wastewater from distilleries, major portion of which is spent wash, is nearly 15 times the total alcohol production. This massive quantity, if disposed untreated can cause considerable stress on the water courses leading to widespread damage to aquatic life.
Distillery waste water handling by evaporation and solid separation basic principle: The technology is based on basic principle of reduction of quantity by concentrating the effluent and subsequently separation of salt and water
The Evaporation & Separation Process:
Distillery Effluent is fed to the vacuum evaporator to concentrate maximum up to 60% solids concentration. The evaporated water is recycled back to fermentation process and concentrate is mixed with the suspended solids separated in decanter. The yeast sludge from the distilleries contains the degradation product of the dead yeasts and organic debris like proteins, fats, vitamins and carbohydrates and the spent wash contains, the above nutrients plus unfermented sugars, amino acids, ammonium phosphates etc. So two types of byproducts viz. the nutrient rich animal feed, and the potassium rich fertilizers may be recovered in a distillery.
Key Features:
- Effluent Volume can be reduced up to 85-87 % (7 times)
- Concentrate of 30% TS is used for bio-composting.
- Concentrate of 70-75% TS after mixing with agro residue can be used as fuel in existing boiler, which give high calorific value
- Condensate water coming from evaporator can be used for
– Make up for cooling water in condenser, and can be recycled
– Washing of equipment
– Dilution of molasses
– Irrigation purposes after maintaining pH
2.Effluent Treatment Plant (Zero Liquid Discharge) for Electroplating Industries:
Electroplating is the process of plating one metal onto another by hydrolysis, most commonly for decorative purposes or to prevent corrosion of a metal. Electroplating is widely used in industries such as automobile, airplanes, electronics, jewelry, and toys. The overall process of electroplating uses an electrolytic cell, which consists of putting a negative charge on the metal and dipping it into a solution that contains metal salt (electrolytes) which contain positively charged metal ions. Then, due to the negative and positive charges, the two metals are attracted to each other.
The effluent from the Electroplating Industries is generally low in solids content and contains metals like chromium and manganese in the effluent. The pollutants are invariably hazardous, as the effluents contaminate air, water and soil. Some of the polluting agents have deleterious effect on human health, examples being cadmium, lead, nickel etc. The environmental load in electroplating industry mainly consists of process waste water, hydroxide sludge and sulphuric acid.
Electroplating waste water handling by evaporation and solid separation basic principle: The technology is based on basic principle of reduction of quantity by concentrating the effluent and subsequently separation of salt and water
The Evaporation & Separation Process:
First of all effluent of Electroplating Industry is neutralized. After that the effluent is preheated and then fed to Evaporator for concentration. After concentration, the concentrate is dried. This dried powder can be used as solid waste disposal or as a land fill.
The condensate obtained from the evaporator is clean and colourless liquid and it can be used back in the plant as soft water.
Key Features:
- ZERO Liquid Discharge
- Low Operating Cost
- User Friendly
- Easily Upgradeable
- Less Downtime for Maintenance
- Applicable for CDM Benefit
3. Effluent Treatment Plant (Zero Liquid Discharge) for Pharmaceutical and Bulk Drug Industries:
The pharmaceutical industry develops, produces, and markets drugs or pharmaceuticals licensed for use as medications.
Wastewater pollution is the main issue of this sector. Pharmaceutical and Bulk Drug industries generates about Gallons of waste water processed depending upon the process employed and product manufactured. In pharmaceutical and Bulk Drug industries wastewater is mainly generated through the washing activities of the equipment and is highly polluted because of presence of substantial amounts of organic pollutants.
Pharmaceutical and Bulk Drug waste water handling by evaporation and solid separation basic principle: The technology is based on basic principle of reduction of quantity by concentrating the effluent and subsequently separation of salt and water
The Evaporation & Separation Process:
For the purpose of treating this effluent, Evaporation and Drying methods are used. The effluent containing high amount of organics is heated in a reboiler and passed through a Stripper Column to strip off the maximum low boiling organic solvents and their vapours are condensed using a condenser. These condensed vapours are partially refluxed back to the stripper to enrich the column and rest of the condensate (solvent) is collected separately and can be incinerated in an incinerator for making the facility a complete zero pollution plant. The output liquid stream from the bottom of the Stripper Column enters the Multiple Effect Falling Film Evaporator. After concentration in the Evaporator, we get a concentrated stream of effluent which can be then further concentrated and condensate water which can be used back in the industry
With the help of this technology, effluent concentrate is dried to a baggable powder with 6-8 % moisture content, which can be reused as a Land filling/Handover to authorized recycler.
Key Features:
- User Friendly
- Easily Upgradable
- Low Operating Cost
- Zero Liquid Discharge
- Highest Steam Economy
- Applicable for CDM Benefit
- Less Downtime for Maintenance
- Fully Customized Designed System
- Lowest Operation & Maintenance Cost
- Generation of Reusable Condensate Water
- Conversion of liquid waste water to solid waste for TSDF
- Removal of Solvent from High COD Stream using stripper column
4. Effluent Treatment Plant (Zero Liquid Discharge) for Pulp & Paper Industries:
Paper is a major product of the forestry industry, and is used widely in our society. Paper is made by pulping wood, bleaching this pulp and then spreading it out into sheets to make it into paper. At various stages of the process, chemicals are used to give the paper particular properties, such as the bleaching chemicals that make paper white.
In pulp mills spent liquor produced during washing of pulp after cooking with Caustic is highly toxic and this cannot be discharged. The dilute liquor from the pulp washing (containing the dissolved inorganic and organic solids) is called “black liquor”.
Pulp & Paper waste water handling by evaporation and solid separation basic principle: The technology is based on basic principle of reduction of quantity by concentrating the effluent and subsequently separation of salt and water.
The Evaporation & Separation Process:
The black liquor from the pulp washing contains 15-17% solids, and this needs to be concentrated to about 60-70% solids before it can be burnt in the recovery furnace. “Spill liquors” may also be recovered from various places in the mill, and these dilute liquors supply further amounts of water, which needs to be evaporated. Evaporation is carried out using multiple effects, normally 5 to 7 effects in series.
First of all effluent is neutralized and then for burning this liquor, it is evaporated in Multiple Effect Evaporator to the desired concentration i.e. 48% in case of conventional recovery or 25 % in case of non conventional systems and then subsequently incinerated.
In case of conventional method of recovery, inorganic chemicals are collected in molten form named smelt. The smelt when dissolved in hot water becomes green liquor (maximum sodium carbonate) which is further treated with lime to produce sodium hydroxide which is reused in pulp mill.
In case of non-conventional method of recovery, liquor at 25% TS is further concentrated to 50 % in direct contact flue gas evaporator and burnt in fluidized bed reactor in which inorganic chemicals are recovered at pre-melting stage in the form of soda ash pellets which are sold in the market.
Key Features:
- Zero Liquid Discharge System.
- Produce Black Liquor Concentrate.
- Highly Energy Efficient
- Minimum Space requirement.
- Fully Customized Design System.
- Low Operating Cost.
- Operator friendly.