Waste Water Treatment

Why we need Waste Water Treatment Plant (WWTP)?

As the world has industrialized and its population has grown, the problem of water pollution has intensified. With numerous factories having no choice, inject untreated effluents directly into the ground, contaminating underground aquifers.

Another cause of water contamination is improper strategy of sewage treatment. Since human waste contain bacteria that can cause disease. Once water becomes infected with these bacteria, it becomes a health hazard. There are following sources of sewerage effluent as:

  • Residential apartment
  • Commercial complex
  • Public amenities/convenience
  • Labour camp/Defence/Refugee camp
  • Resorts & clubs
  • Factories/Industries

Waste management is the collection, transport, processing, recycling or disposal, and monitoring of waste materials, without affecting humans and other life systems and without disturbing the environment. The term usually relates to materials produced by human activity either at home / office / industry / agricultural fields / mines etc., and is generally undertaken to reduce their effect on health, the environment or aesthetics. Waste Management is also carried out to recover resources from it.

Sewage / Effluent Treatment Plant is a facility designed to receive the waste from domestic, commercial and industrial sources and to remove materials (containing physical, chemical and biological contaminants) that damage water quality and compromise public health and safety when discharged into water receiving systems.

Key Components :

  • Sewage / Effluent collection tank: Where preliminary, effluent is collected.
  • Screening: Any solid materials like; iron particles, stones, plastic items, grass weed, polythene paper, cloth etc are checked through bar screen filter to avoid any damages of the transferring pump.
  • Screening: Any solid materials like; iron particles, stones, plastic items, grass weed, polythene paper, cloth etc are checked through bar screen filter to avoid any damages of the transferring pump.
  • Equalization tank: In which, suspended materials are mixed properly to make a homogeneous mixture. An steering arrangement is employed in the tank.
  • Neutralization tank: Some chemicals are added for maintaining Ph, and for quick flocculation.
  • Sludge tank: After neutralization and flocculation of effluent, the suspended matter undergoes settling which is called sludge. The tank is used for sludge collection.
  • Aeration tank: A mechanical aeration system is adopted in the tank for growth of biomass which are easily coagulates suspended and dissolved particle.
  • Bio reactor: Where biomass is developed in aerobic condition.
  • Lamella filtration: After aeration of effluent, it allows to further settling with certain contact time.
  • Gradually all solids matter deposits at the bottom while the liquid water passed to PSF
  • Pressure sand filter (PSF): Used to remove suspended impurities from the water.
  • Activated carbon filter (ACF): De-odorize any smell in the water.
  • UV/chlorination disinfection: After de-odorizing of water, it is disinfected by either UV (ultraviolet radiation) or with chlorine. So that all types of micro-organisms, pathogens are killed before going to further use.
  • Final water discharge: The discharged water is used for various purpose like, gardening, cleaning, irrigation, car washing

How can bacteria be removed from water?

Bacteria and other microorganisms are removed from water through disinfection. This means that certain substances are added to kill the bacteria, these are called biocides. Sometimes disinfection can also be done with UV-light.

What is aerobic water treatment?

When bacteria are used for water purification there are two sorts of transfer; one of these is aerobic transfer. This means, that bacteria that are oxygen dependent are converting the contaminants in the water. Aerobic bacteria can only convert compounds when plenty of oxygen is present, because they need it to perform any kind of chemical conversion. Usually the products they convert the contaminants to are carbon dioxide and water.

How to control odor of waste Water Treatment plan ?

Our package sewage treatment plant has a relatively low odor profile. Our treatment reactors are all sealed and installed below grade. This limits the amount of odor that can escape. In addition we can install an activated carbon scrubber system to clean the collected off gasses before releasing them to the atmosphere. We can also use sludge bagging systems to dewater wasted solids before disposal thus eliminating another possible source of odor.

How to you handle wasted solids?

Wasted solids (sludge & screenings) can be collected and dewatered for removal by a licensed sewage hauling company. Sludge holding tanks can be emptied by a septic hauler for disposal. 

What levels of treatment do your facilities provide

Whatever levels are needed. The design and equipment selection for our facilities is based on the treatment levels required by the wastewater treatment plant permit and local regulatory agencies. We have facilities that meet the strictest effluent limits in many states and climates. Whatever treatment level you need, we can accomplish it.

Can wastewater treatment plants be built in phases?

Yes. Our facilities can be built in phases with the being constructed to the full build out capacity and only the necessary tanks and equipment being installed for the current capacity. When additional capacity is needed, the additional tanks and equipment can be added to expand the capacity of your facility. Wastewater Treatment Plant Phasing is an effective way to lower upfront costs. 

With newer technology out such as MBRs, why use an older treatment technology?

Newer technology does not mean it is better. MBRs can cost substantially more to operate and maintain than extended aeration systems. Our treatment process is time tested, effective and reliable. 

What is the difference between a onsite civil and a Package Plant?

Package plants are predesigned, prefabricated and preassembled. They arrive completed on a flatbed truck. There is little to no flexibility in regards to configuration. Shubham ‘s facilities are custom designed and constructed specifically for your project to meet your needs. In addition, finding replacement parts is easier as the equipment used in facilities are widely available on the open market from many different suppliers. 

What is the most major consideration with utilizing a waste water treatment plant?

We almost always begin with effluent disposal. The method of effluent disposal will dictate the required treatment level and therefore the equipment that will be necessary to achieve it. 

What is the typical stage of a development that Shubham becomes involved?

All stages. Most of our clients contact us during the early design stage of a project. Because of the potential length of the permitting process, it is beneficial that we become involved at a very early stage of a development. We can however begin our involvement at any point. 

Can you provide preliminary site plans for my project's facility?

Yes. We at shubham, will usually provide a basic site plan based on a past facility we have completed that is the same or similar to what we anticipate you will need. Once we enter into a contract and the details of the project get worked out, we will develop a plan specific to your project. 

Can Shubham help to operate & maintain facility?

Yes. We can contract a local operator to run your facility. The certification and staffing levels required vary by region. We will usually take a supporting role performing inspections and responding to any issues that may arise. 

Does Shubham operate facilities?

YES, Shubham does operate wastewater treatment plants. We provide plant startup, operations training, consulting and will even contract operations staff as a service to our clients but we do operate the plants ourselves.

What is waste Water Treatment & Its purpose?

Wastewater Treatment Purpose: To manage water discharged from homes, businesses, and industries to reduce the threat of water pollution. Wastewater Treatment

  • Pre-treatment

Occurs in business or industry prior to discharge
Prevention of toxic chemicals or excess nutrients being discharged in wastewater

  • Preliminary Treatment

removes large objects and non-degradable materials

protects pumps and equipment from damage

bar screen and grit chamber

  • Bar Screen

catches large objects that have gotten into sewer system such as bricks, bottles, pieces of wood, etc.

  • Grit Chamber

removes rocks, gravel, broken glass, etc.

  • Mesh Screen

removes diapers, combs, towels, plastic bags, syringes, etc.

  • Measurement and sampling at the inlet structure

a flow meter continuously records the volume of water entering the treatment plant

water samples are taken for determination of suspended solids and B.O.D

  • Suspended Solids

the quantity of solid materials floating in the water column

  • B.O.D. = Biochemical Oxygen Demand

a measure of the amount of oxygen required to aerobically decompose organic matter in the water

Measurements of Suspended Solids and B.O.D. indicate the effectiveness of treatment processes

Both Suspended Solids and B.O.D. decrease as water moves through the wastewater treatment processes

  • Primary Treatment

a physical process

wastewater flow is slowed down and suspended solids settle to the bottom by gravity

the material that settles is called sludge or biosolids

  • Sludge from the primary sedimentation tanks is pumped to the sludge thickener.

more settling occurs to concentrate the sludge prior to disposal

Primary treatment reduces the suspended solids and the B.O.D. of the wastewater.

From the primary treatment tanks water is pumped to the trickling filter for secondary treatment.

Secondary treatment will further reduce the suspended solids and B.O.D. of the wastewater

  • Secondary Treatment

Secondary treatment is a biological process

Utilizes bacteria and algae to metabolize organic matter in the wastewater

In Cape Girardeau secondary treatment occurs on the trickling filter

the trickling filter does not “filter” the water

water runs over a plastic media and organisms clinging to the media remove organic matter from the water

From secondary treatment on the trickling filter water flows to the final clarifiers for further removal of sludge.

The final clarifiers are another set of primary sedimentation tanks.

Which are the process Waste Water Treatment

Before we go in to the discussions of various aerobic biological treatment processes, it is important to briefly discuss the terms aerobic and anaerobic. Aerobic, as the title suggests, means in the presence of air (oxygen); while anaerobic means in the absence of air (oxygen). These two terms are directly related to the type of bacteria or microorganisms that are involved in the degradation of organic impurities in a given wastewater and the operating conditions of the bioreactor. Therefore, aerobic treatment processes take place in the presence of air and utilize those microorganisms (also called aerobes), which use molecular/free oxygen to assimilate organic impurities i.e. convert them in to carbon dioxide, water and biomass. The anaerobic treatment processes, on other hand take place in the absence of air (and thus molecular/free oxygen) by those microorganisms (also called anaerobes) which do not require air (molecular/free oxygen) to assimilate organic impurities. The final products of organic assimilation in anaerobic treatment are methane and carbon dioxide gas and biomass. The pictures in Fig. 1 and 2 depict simplified principles of the

How this Process is different from each other?

Parameter

Aerobic Treatment

Anaerobic Treatment

Process Principle• Microbial reactions take place in thepresence of molecular/ free oxygen

• Reactions products are carbondioxide, water and excess biomass

• Microbial reactions take place in the absence of molecular/ free oxygen

• Reactions products are carbon dioxide, methane and excess biomass

ApplicationsWastewater with low to medium organicimpurities (COD < 1000 ppm) and forwastewater that are difficult to biodegradee.g. municipal sewage, refinery wastewateretc.Wastewater with medium to high organicimpurities (COD > 1000 ppm) and easily biodegradable wastewater e.g. food and beverage wastewater rich in starch/sugar/alcohol
Reaction KineticRelatively fastRelatively Slow
Net Sludge YieldRelatively highRelatively low (generally one fifth to one tenth of aerobic treatment processes)
Post TreatmentTypically direct discharge or filtration/disinfectionInvariably followed by aerobic treatment
Foot-PrintRelatively largeRelatively small and compact
Capital InvestmentRelatively highRelatively low with pay back
Example TechnologiesActivated Sludge, Extended Aerations, Oxidation Ditch , MBR Fixed Film ProcessContinuously  Stirred Tank Reactor, digester, up flow , anaerobic Sludge Blanket

Which is the most appropriate & Most suitable Technology ?

 Comparison:

Comparison of Aerobic Biological Treatment Options

ParameterConventional ASPSequencing batch reactor (SBR)Integrated Fixed Film Activated Sludge (IFAS) SystemMBR
Treated Effluent QualityMeets specifieddischarge standardswith additional Filtration StepMeets specifieddischarge standardswith additional Filtration StepMeets/ exceeds specifieddischarge standards withadditional filtration stepExceeds specified discharge stan­dards without additional filtration step. Very good for recycle provided TDS level permits
Ability to adjust to variable hydraulic and pollutant loadingAverageVery goodVery goodVery good
Pretreatment RequirementSuspended impurities e.g. oil & grease and TSS removalSuspended impurities e.g. oil & grease and TSS removalSuspended impurities e.g. oil & grease and TSS removalFine screening for suspended impurities like hair and almost complete oil & grease removal
Ability to cope with ingress of oilAverageGoodAveragePoor & detrimental to membrane
Secondary Clari­fier RequirementNeededAeration Basin actsas clarifierNeededClarifier is replaced byMembrane filtration
Complexity to operate & controlSimple, but not operator friendlyOperator friendlyOperator friendlyRequires skilled operators
Reliability & Proven-ness of TechnologyAverageVery goodVery goodLimited references in industrial applications
Capital CostLowLowHighVery High
Operating CostLowLowHighVery High
Space RequirementHighLowAverageLow

How does MBBR & MBR differs?

Specification

MBR Plant

MBBR Plant

Capital Investment

High

Low

Footprint

Low

Low

Flow Tolerance

Low

High

Aeration Blowers

Required

Required

Recirculation Pumps

Required

Not Required

Air Scouring Blowers

Required

Not Required

Screening

Requirements

High

Low

Chemical Usage

High

N/A

Operational Difficulty

High

Low

Comparison between various technology:

Comparison: 800 m3/day

MBBR

RBC

Activated Sludge

SBR

No residualsuspended solidsNo residual suspendedsolidsRequires residualsuspended solids(MLSS)Requires residualsuspended solids(MLSS)
Self regulating, nooperator adjustmentsSelf regulating, nooperator adjustmentsOperator adjusts MLSSLevelsOperator adjusts MLSSLevels
Single pass flowthroughSingle pass flowThroughMLSS sludge recycledback through plantMay or may not requireMLSS recycle
1 hour retention time(based on 800m3/d)4 hours retention time4 hours retention time5 hours retention time(includes clarification)
8.25 m2 treatmentArea64 m2 treatment area33.75 m2 treatment area31.5 m2 treatment area(includes clarification)
Not affected by highFlowsBiology stripped ofmedia with high flowsMLSS can be flushedout with high flowsRarely affected by highFlows
Low mechanicalequipmentHigh mechanicalequipmentModerate mechanicalequipmentLow mechanicalEquipment
Stable nutrientremovalUnstable nutrientremovalUnstable nutrientremovalStable nutrient removal

Water Treatment

What is hard water?

When water is referred to as ‘hard’ this simply means, that it contains more minerals than ordinary water. These are especially the minerals calcium and magnesium. The degree of hardness of the water increases, when more calcium and magnesium dissolves.

Magnesium and calcium are positively charged ions. Because of their presence, other positively charged ions will dissolve less easily in hard water than in water that does not contain calcium and magnesium.
This is the cause of the fact that soap doesn’t really dissolve in hard water.

Which industries attach value to hardness of water?

In many industrial applications, such as the drinking water preparation, in breweries and in sodas, but also for cooling- and boiler feed water the hardness of the water is very important.

What is water purification?

Water purification generally means freeing water from any kind of impurity it contains, such as contaminants or micro organisms. Water purification is not a very one-sided process; the purification process contains many steps. The steps that need to be progressed depend on the kind of impurities that are found in the water. This can differ very much for different types of water.
In which ways is polluted water treated?

Settling

Before the purification process begins some contaminants, such as oil, can be settled in a settling tank. They can then be removed easily, after they have reached the bottom of the tank.

Removal of dangerous microorganisms

Often polluted water has to be freed from microorganisms. The water is than disinfected, usually by means of chlorination.

Removal of dissolved solids

Microorganisms are not only a threat to water; they can also be an advantage when it comes to water purification processes. They can convert harmful contaminants to harmless substances. This biological purification process usually takes a long time and it is only used for water that is polluted with contaminants that the microorganisms, usually bacteria, can convert.

Physical/ chemical techniques

When treatment by microorganisms is not an option we often use different treatment techniques, called physical/ chemical treatment techniques. Chemical treatment often deals with the addition of certain chemicals, in order to make sure that the contaminants change structure and can then be removed more easily. Fertilizers such as nitrates are removed this way. Removal of contaminants can also be done through more difficult specific chemical processes. It takes a lot of education to fully understand these purification steps. Physical treatment usually deals with purification steps such as filtration.

Water softening

What is water softening?

When water contains a significant amount of calcium and magnesium, it is called hard water. Hard water is known to clog pipes and to complicate soap and detergent dissolving in water. Water softening is a technique that serves the removal of the ions that cause the water to be hard, in most cases calcium and magnesium ions. Iron ions may also be removed during softening. The best way to soften water is to use a water softener unit and connect it directly to the water supply. 

What is a water softener?

A water softener is a unit that is used to soften water, by removing the minerals that cause the water to be hard. 

Why is water softening applied?

Water softening is an important process, because the hardness of water in households and companies is reduced during this process. When water is hard, it can clog pipes and soap will dissolve in it less easily. Water softening can prevent these negative effects.

Hard water causes a higher risk of lime scale deposits in household water systems. Due to this lime scale build-up, pipes are blocked and the efficiency of hot boilers and tanks is reduced. This increases the cost of domestic water heating by about fifteen to twenty percent.

Another negative effect of lime scale is that it has damaging effects on household machinery, such as laundry machines. Water softening means expanding the life span of household machine, such as laundry machines, and thelife span of pipelines. It also contributes to the improved working, and longer lifespan of solar heating systems, air conditioning units and many other water-based applications.

What does a water softener do?

Water softeners are specific ion exchangers that are designed to remove ions, which are positively charged. Softeners mainly remove calcium (Ca2+) and magnesium (Mg2+) ions. Calcium and magnesium are often referred to as ‘hardness minerals’.

Softeners are sometimes even applied to remove iron. The softening devices are able to remove up to five milligrams per litre (5 mg/L) of dissolved iron.

Softeners can operate automatic, semi-automatic, or manual. Each type is rated on the amount of hardness it can remove before regeneration is necessary.

A water softener collects hardness minerals within its conditioning tank and from time to time flushes them away to drain.

Ion exchangers are often used for water softening. When an ion exchanger is applied for water softening, it will replace the calcium and magnesium ions in the water with other ions, for instance sodium or potassium. The exchanger ions are added to the ion exchanger reservoir as sodium and potassium salts (NaCl and KCl).

How long does a water softener last?

A good water softener will last many years. Softeners that were supplied in the 1980’s may still work, and many need little maintenance, besides filling them with salt occasionally.

Softening salts

Which types of salt are sold for application in a water softener?

For water softening, three types of salt are generally sold:
– Rock salt
– Solar salt
– Evaporated salt

  • Rock salt as a mineral occurs naturally in the ground. It is obtained from underground salt deposits by traditional mining methods. It contains between ninety-eight and ninety-nine percent sodium chloride. It has a water insolubility level of about 0.5-1.5%, being mainly calcium sulphate. Its most important component is calcium sulphate.
  • Solar salt as a natural product is obtained mainly through evaporation of seawater. It contains 85% sodium chloride. It has a water insolubility level of less than 0.03%. It is usually sold in crystal form. Sometimes it is also sold in pellets.
  • Evaporated salt is obtained through mining underground salt deposits of dissolving salt. The moisture is then evaporated, using energy from natural gas or coal. Evaporated salt contains between 99.6 and 99.99% sodium chloride.

Should we use rock salt, evaporated salt or solar salt in a water softener?

Rock salt contains a lot of matter that is not water-soluble. As a result, the softening reservoirs have to be cleaned much more regularly, when rock salt is used. Rock salt is cheaper than evaporated salt and solar salt, but reservoir cleaning may take up a lot of your time and energy.

Solar salt contains a bit more water-insoluble matter than evaporated salt. When one makes a decision about which salt to use, consideration should be given to how much salt is used, how often the softener needs cleanout, and the softener design. If salt usage is low, the products could be used alternately.

If salt usage is high, insoluble salts will build up faster when using solar salt. Additionally, the reservoir will need more frequent cleaning. In that case evaporated salt is recommended.

Is it harmful to mix different kinds of salt in a water softener?

It is generally not harmful to mix salts in a water softener, but there are types of softeners that are designed for specific water softening products. When using alternative products, these softeners will not function well.

Mixing evaporated salt with rock salt is not recommended, as this could clog the softening reservoir. It is recommended that you allow your unit to go empty of one type of salt before adding another to avoid the occurrence of any problems.

How often should one add salt to a softener?

Salt is usually added to the reservoir during regeneration of the softener. The more often a softener is regenerated, the more often salt needs to be added.

Usually water softeners are checked once a month. To guarantee a satisfactory production of soft water, the salt level should be kept at least half-full at all times.

How come water sometimes does not become softer when salt is added?

Before salt starts working in a water softener it needs a little residence time within the reservoir, since the salt is dissolving slowly. When one immediately starts regeneration after adding salt to the reservoir, the water softener may not work according to standards.

When the water softening does not take place it could also indicate softener malfunction, or a problem with the salt that is applied.

 Softeners maintenance

When does a softener resin need replacement?

When the water does not become soft enough, one should first consider problems with the salt that is used, or mechanical malfunctions of softener components. When these elements are not the cause of the unsatisfactory water softening, it may be time to replace the softener resin, or perhaps even the entire softener.

Through experience we know that most softener resins and ion exchanger resins last about twenty to twenty-five years.

Does a softener brine tank need cleaning?

Usually it is not necessary to clean out a brine tank, unless the salt product being used is high in water-insoluble matter, or there is a serious malfunction of some sort.
If there is a build-up of insoluble matter in the resin, the reservoir should be cleaned out to prevent softener malfunction.

Can brine from softeners damage a septic tank?

The Water Quality Association has performed studies on this subject. These studies have indicated that a properly placed septic tank that works adequately cannot be damaged by brine that is discharged from a water softener. And softened water can sometimes even help reduce the amount of detergents discharged into a septic tank. 

Can a water softener be used with lead pipes?

Lead pipe systems have to be replaced, before softened water can flow through them. Although lead pipe systems in hard water areas may not cause a problem, it is advisable to replace them anyway. When naturally or artificially softened water ends up in these lead pipe systems, it may cause the pickup of lead.  

Can one measure water hardness inline?

Yes, although the measurement system is mainly applied in industrial water softeners.  

BOILER

What is boiler feed water?

Feed water is water added to a boiler to replace evaporation and blow down. In many cases, condensed steam returned to the boiler through the condensate system constitutes much of the feed water. Make-up is any water needed to supplement the returned condensate. The make-up water is usually natural water, either in its raw state or treated by some process before use. Feed water composition therefore depends onthe quality of the make-up water and the amount of condensate returned. 

How pure must feed water be?

Feed water purity is a matter both of quantity of impurities and nature of impurities. Some impurities such as hardness, iron and silica, for example, are of more concern than sodium salts. Feed water purity requirements depend on boiler pressure, design and application. Feed water purity requirements can vary widely. Low-pressure, fire tube boilers require less stringent feed water control than modern high pressure boilers. 

Which impurities form deposits?

Dissolved bicarbonates of calcium and magnesium break down under heat to give off carbon dioxide and form insoluble carbonates. These carbonates may precipitate directly on the boiler metal or form sludge in the boiler water that may deposit on boiler surfaces. Calcium sulfate, upon heating, becomes less soluble. Sulfate and silica generally precipitate directly on the boiler metal and ordinarily do not form sludge. For this reason they are much harder to condition and may cause more difficulties.
Silica is usually not present in very large quantities in water, but under certain conditions it can form an exceedingly hard scale. Suspended or dissolved iron coming in with the feed water will also deposit on the boiler metal. Oil and other process contaminants can form deposits as well as promote deposition of other impurities. Sodium compounds do not deposit under normal circumstances. Sodium deposits can form under unusual circumstances: in a starved tube, a stable steam blanket or under existing porous deposits. 

What is boiler water carryover?

  • Boiler water carryover is the contamination of steam with boiler water solids. There are several common causes of boiler water carryover:
  • Bubbles form on the surface of the boiler water and leave with the steam. Thisfoaming can be compared to the stable foam of soap suds.
  • Spray or mist is thrown up into the steam space by the bursting of rapidly risingbubbles at the steam release surface. This phenomenon is like the effervescence of champagne. No stable foam forms, but droplets of liquid burst from the liquid surface.
  • Priming is a sudden surge of boiler water caused by a rapid change in load. (Uncapping a bottle of charged water produces an effect like this.)
  • Steam contamination may also occur from leakage of water through improperly designed or installed steam-separating equipment in a boiler drum.

What causes foaming?

Very high concentrations of soluble or insoluble solids in boiler water will cause foaming. Specific substances such as alkalis, oils, fats, greases and certain types of organic matter and suspended solids cause foaming. 

Corrosion

What is corrosion?

Stated simply, general corrosion is the reversion of a metal to its ore form. Iron for example, reverts to iron oxide as a result of corrosion. The process of corrosion, however, is a complex electro-chemical reaction. Corrosion may produce general attack over a large metal surface or may result in pinpoint penetration of the metal.

Basic corrosion in boilers results primarily from the reaction of oxygen with the metal. Stresses, pH conditions and chemical corrosion have an important influence and produce different forms of attack.

Where corrosion is usually experienced?

Corrosion may occur in the feed water system as a result of low pH water and the presence of dissolved oxygen and carbon dioxide. On-line boiler corrosion occurs when boiler water alkalinity is too low or too high. When oxygen-bearing water contacts metal, often during idle periods, corrosion can occur. High temperatures and stresses in the boiler metal tend to accelerate the corrosive mechanisms. In the steam and condensate system, corrosion is generally the result of contamination with carbon dioxide and oxygen. Additional contaminants such as ammonia or sulfur-bearing gases may increase attack on copper alloys in the system. 

What other materials can cause boiler corrosion?

Excessive chelate residuals (in excess of 20 ppm as CaCO3) or improperly applied chelate programs may produce boiler system corrosion. Concentrating boiler solids at ahigh heat input area might also produce boiler corrosion. To minimize the chance of corrosion, follow the recommendations of your Nalco water treatment consultant.  

What problems are caused by corrosion?

Corrosion causes difficulty from two respects. The first is deterioration of the metal itself and the second is deposition of the corrosion products in high heat release areas of the boiler. Uniform corrosion of boiler surfaces is seldom of real concern. All boilers experience a small amount of general corrosion. Corrosion takes many insidious forms, however, and deep pits resulting in only a minimal total iron loss may cause penetration and leakage in boiler tubes. Corrosion beneath certain types of boiler deposits can so weaken the metal that tube failure may occur. In steam condensate systems, replacement of lines and equipment due to corrosion can be costly. 

How is boiler corrosion measured?

With the trend toward higher heat fluxes in today’s modern boilers, corrosion has become an important factor in power plant operation. When iron corrodes, hydrogen gas, which can be measured in the steam, is released. Measuring the amount of hydrogen gas released can detect immediate fluctuations in load, boiler water conditions or fuel changes. This information when interpreted by an experienced, well trained engineer can indicate if corrosive conditions exist in an operating boiler. 

What measures are taken to prevent boiler system corrosion?

The most common methods for prevention of corrosion include:

  • Removing dissolved oxygen from the feedwater
  • Maintaining alkaline conditions in the boiler water
  • Keeping internal surfaces clean
  • Protecting boilers during out-of-service intervals
  • Counteracting corrosive gases in steam and condensate systems with chemical treatment

The selection and control of chemicals for preventing corrosion require a thorough understanding of the causes and corrective measures. Your Nalco representative provides this expertise.

What is clarification?

Clarification is the removal of suspended matter and color from water supplies. The suspended matter may consist of large particles that settle out readily. In these cases, clarification equipment merely involves the use of settling basins or filters. Most often, suspended matter in water consists of particles so small that they do not settle out, but instead pass through filters. The removal of these finely divided or colloidal substances therefore requires the use of coagulants.  

What is coagulation? What is flocculation?

Coagulation is charge neutralization of finely divided or colloidal impurities. Colloidal particles have large surface areas that keep them in suspension. In addition, the particles have negative electrical charges, which cause them to repel each other and resist adhering together. Coagulation requires neutralization of the negative charges, providing an agglomeration point for other suspended particles. Flocculation is thebridging together of the coagulated particles.  

What is chemical precipitation?

 In precipitation processes, the chemicals added react with dissolved minerals in the water to produce a relatively insoluble reaction product. Precipitation methods reduce dissolved hardness, alkalinity and, in some cases, silica. The most common example of chemical precipitation in water treatment is lime-soda softening.

Ion Exchange

What is ion exchange?

When minerals dissolve in water, they form electrically charged particles called ions. Calcium bicarbonate, for example, forms a calcium ion with positive charges (a cation) and a bicarbonate ion with negative charges (an anion).Certain natural and synthetic materials have the ability to remove mineral ions from water in exchange for others. For example, calcium and magnesium ions can be exchanged for sodium ions by simply passing water through a cation exchange softener. 

What are the various types of ion exchange resins?

There are two types of ion exchange resins: cation and anion. Cation exchange resins react only with positively charged ions such as Ca+2 and Mg+2. Anion exchange resins react only with the negatively charged ions such as bicarbonate (HCO3-) and sulfate (SO4-2).

Although there are several types of cation exchange resins, they usually operate on either a sodium or hydrogen “cycle”. A “sodium cycle” exchanger replaces cation with sodium; a “hydrogen cycle” exchanger replaces cation with hydrogen. The two types of anion resins are: weak base and strong base. Weak base resins will not take out carbon dioxide or silica (actually carbonic acid and siliceous acid), Strong base anion resins, on the other hand, can reduce silica and carbon dioxide as well as strong acid anions to very low values. Strong base anion resins are generally operated on a hydroxide cycle. Dealkalization reduces alkalinity through chloride anion exchange.

What is ion exchange regeneration?

Ion exchange resins have only a limited capacity for removing ions from water. Reversing the ion exchange process, regeneration, returns the resin to its original condition. Regeneration involves taking the unit off line and treating it with a concentrated solution of the regenerate. The ion exchange resin releases ions previously removed; these ions are rinsed out of the resin vessel. The ion exchange unit is then ready for further service. In the case of cation exchangers operating on the sodium cycle, salt (NaCl) replenishes the sodium capacity or acid (H2SO4 or HCl) replenishes the hydrogen capacity. Anion
exchangers are regenerated with caustic (NaOH) or ammonium hydroxide (NH4OH) to replenish the hydroxide ions. Salt (NaCl) may be used to regenerate anion resins in the chloride form for de alkalization.

What is the purpose of deaeration?

Before the feed water enters the boiler, oxygen must be removed. Feed water deaeration removes dissolved oxygen by heating the water with steam in a de aerating heater or deaerators. A steam vents transports the oxygen out of the deaerator.There are two basic types of steam deaerators: spray and tray. In the spray deaerator,a jet of steam mixes intimately with the feed water being sprayed into the unit. In the tray type, the incoming waterfalls over a series of trays, where it is broken into small droplets and mixed with the steam. Tray-type deaerators also increase the residence time in the deaerators section  

Reverse Osmosis

What is reverse osmosis?

To understand reverse osmosis (RO), one must first understand osmosis. Osmosis uses a semi-permeable membrane that allows ions to pass from a more concentrated solution to a less concentrated solution without allowing the reverse to occur. Reverse osmosis overcomes the osmotic pressure with a higher artificial pressure to reverse the process and concentrate the dissolved solids on one side of the membrane. Normal operating pressures are 300 to 900 psi. Reverse osmosis will reduce the dissolved solids of the raw water, making the final effluent ready for further pretreatment. Although sometimes expensive, this process can be used on any type water. 

Understanding Reverse Osmosis

Reverse Osmosis, commonly referred to as RO, is a process where you demineralize or deionize water by pushing it under pressure through a semi-permeable Reverse Osmosis Membrane.  

Osmosis

To understand the purpose and process of Reverse Osmosis you must first understand the naturally occurring process of Osmosis.

Osmosis is a naturally occurring phenomenon and one of the most important processes in nature. It is a process where a weaker saline solution will tend to migrate to a strong saline solution. Examples of osmosis are when plant roots absorb water from the soil and our kidneys absorb water from our blood.

Below is a diagram which shows how osmosis works. A solution that is less concentrated will have a natural tendency to migrate to a solution with a higher concentration. For example, if you had a container full of water with a low salt concentration and another container full of water with a high salt concentration and they were separated by a semi-permeable membrane, then the water with the lower salt concentration would begin to migrate towards the water container with the higher salt concentration.

How does Reverse Osmosis work?

Reverse Osmosis works by using a high pressure pump to increase the pressure on the salt side of the RO and force the water across the semi-permeable RO membrane, leaving almost all (around 95% to 99%) of dissolved salts behind in the reject stream. The amount of pressure required depends on the salt concentration of the feed water. The more concentrated the feed water, the more pressure is required to overcome the osmotic pressure.
The desalinated water that is dematerialized or deionized, is called permeate (or product) water. The water stream that carries the concentrated contaminants that did not pass through the RO membrane is called the reject (or concentrate) stream.  

What will Reverse Osmosis remove from water?

Reverse Osmosis is capable of removing up to 99%+ of the dissolved salts (ions), particles, colloids, organics, bacteria and pyrogens from the feed water (although an RO system should not be relied upon to remove 100% of bacteria and viruses). An RO membrane rejects contaminants based on their size and charge. Any contaminant that has a molecular weight greater than 200 is likely rejected by a properly running RO system (for comparison a water molecule has a MW of 18). Likewise, the greater the ionic charge of the contaminant, the more likely it will be unable to pass through the RO membrane. For example, a sodium ion has only one charge (monovalent) and is not rejected by the RO membrane as well as calcium for example, which has two charges. Likewise, this is why an RO system does not remove gases such as CO2 very well because they are not highly ionized (charged) while in solution and have a very low molecular weight. Because an RO system does not remove gases, the permeate water can have a slightly lower than normal pH level depending on CO2 levels in the feed water as the CO2 is converted to carbonic acid.
Reverse Osmosis is very effective in treating brackish, surface and ground water for both large and small flows applications. Some examples of industries that use RO water include pharmaceutical, boiler feed water, food and beverage, metal finishing and semiconductor manufacturing to name a few. 

Filtration

What is Importance of Filtration in Industries?

The industrial world relies on a lot of different processes to keep things operating smoothly. With so much machinery, chemicals and other materials involved over such a wide range of industries, every single process has its place and plays a role. Filtration is one process that is evident in many different industries and is crucial for removing unwanted particles from water and other substances. The filtration process may differ slightly from plant to plant and industry to industry, but will typically include elements of absorption, sedimentation, interception, diffusion and straining. Industrial water filtration is one area of filtration that is quite important for a variety of different reasons.

In an industrial setting, water filtration refers to the removal of particles or suspended solids from water or wastewater. The particles that need to be removed are typically larger than 0.5 microns and the action is accomplished using commercial industrial filters. Depending on the scope of the operation, one filter may be sufficient or you may need several. Sometimes, a combination of filters in a specific sequence or order is necessary to remove all of the solids and keep the process running smoothly.

Which type of filters are used in Industries ?

Some of the different types of industrial filters that are used for water filtration include:

  •  Bag filters
  •  Cartridge filters
  •  Multimedia filters
  •  Dual media filters
  •  Sand filters
  •  Screen filters

Since filtration is such serious business, great care is usually taken to determine which kind of filter will do the best job. This often includes laboratory tests with a wide range of samples. Once the results are in, you will know if you need bag filters, cartridge filters or any of the other possible choices

Which are the industries need a filtration?

Industrial water filtration is an important process across a range of different industries, for a range of different reasons. Products you use on a daily basis in your home, at work or even out in nature, may depend on industrial water filtration as part of their process. Some of the common industries that rely on industrial water filtration include:

  • Chemicals
  • Electronics
  • Food and Beverage
  • Pharmaceutical
  • Oil and Gas
  • Air and Gas
  • Pulp and Paper
  • Power
  • Coolants

What are the risks of Poor Industrial Water Filtration?

Just as good industrial water filtration through the proper use of bag filters and other filters will enhance the process, poor filtration can lead to a host of different problems.

  • Depending on the specific industry in question, the consequences may range from regulatory to business to health.
  • Poor filtration might lead to contamination of an order or entire batch of product, it might lead to recalls of particular products, or t might put a company on the wrong side of government laws and regulations.
  • In industries such as the pharmaceutical industry, improper filtration could lead to serious human health consequences, which would then lead to serious legal consequences for the company in question.
  • No matter the industry, it pays to take industrial water filtration very seriously and follow all the necessary guidelines to ensure that aspect is always operating at full capacity.

What is ultra filtration ?

Ultrafiltration (UF) is a pressure-driven process that removes emulsified oils, metal hydroxides, colloids, emulsions, dispersed material, suspended solids, and other large molecular weight materials from water and other solutions. UF membranes are characterized by their molecular weightcut-off. UF excels at the clarification of solutions containing suspended solids, bacteria, and high concentrations of macromolecules, including oil and water, fruit juice, milk and whey, electrocoat paints, pharmaceuticals, poly-vinyl alcohol and indigo, potable water, and tertiary wastewater.  

Why cooling water System is Important?

Cooling water systems are an integral part of process operations in many industries. For continuous plant productivity, these systems require proper chemical treatment and preventive maintenance.

Most industrial production processes need cooling water for efficient, proper operation. Refineries, steel mills, petrochemical plants, manufacturing facilities, food plants, large buildings, chemical processing plants, and electric utilities all rely on the cooling water system to do its job. Cooling water systems control temperatures and pressures by transferring heat from hot process fluids into the cooling water, which carries the heat away. As this happens, the cooling water heats upend must be either cooled before it can be used again or replaced with fresh makeup water. The total value of the production process will be sustained only if the cooling system can maintain the proper process temperature and pressure. The cooling system design, effectiveness and efficiency depend on the type of process being cooled, the characteristics of the water and environmental considerations.

Ultra filter vs. Conventional Filter

Ultra filter vs. Conventional Filter

Ultra filtration, like reverse osmosis, is a cross-flow separation process. Here liquid stream to be treated (feed) flows tangentially along the membrane surface, thereby producing two streams. The stream of liquid that comes through the membrane is called permeate. The type and amount of species left in the permeate will depend on the characteristics of the membrane, the operating conditions, and the quality of feed. The other liquid stream is called concentrate and gets progressively concentrated in those species removed by the membrane. In cross-flow separation, therefore, the membrane itself does not act as a collector of ions, molecules, or colloids but merely as a barrier to these species.

Conventional filters such as media filters or cartridge filters, on the other hand, only remove suspended solids by trapping these in the pores of the filter-media. These filters therefore act as depositories of suspended solids and have to be cleaned or replaced frequently. Conventional filters are used upstream from the membrane system to remove relatively large suspended solids and to let the membrane do the job of removing fine particles and dissolved solids. In ultrafiltration, for many applications, no prefilters are used and ultrafiltration modules concentrate all of the suspended and emulsified materials

Ultrafiltration Membranes

Ultrafiltration Membrane modules come in plate-and-frame, spiral-wound, and tubular configurations. All configurations have been used successfully in different process applications. Each configuration is specially suited for some specific applications and there are many applications where more than one configuration is appropriate. For high purity water, spiral-wound and capillary configurations are generally used. The configuration selected depends on the type and concentration of colloidal material or emulsion. For more concentrated solutions, more open configurations like plate-and-frame and tubular are used. In all configurations the optimum system design must take into consideration the flow velocity, pressure drop, power consumption, membrane fouling and module cost.