Ground Water - Sulfate Removal Technologies

Sulfate Removal Technologies

Magnesium sulfate crystals photographed under polarized light

By Mark Reinsel, Ph.D., P.E., Apex Engineering, PLLC

Sulfate concentrations in water have come under increasing scrutiny from regulatory authorities over the past two decades.  In contrast to contaminants such as nitrate, arsenic, and heavy metals, sulfate has no primary standard for drinking water or aquatic life.  However, the secondary standard for drinking water in the U.S. is 250 mg/L and concentrations above 600 mg/L may create laxative effects.  In Minnesota, future sulfate discharges may be limited to as low as 10 mg/L (an unenforced standard that is currently under review) to protect wild rice habitat.  Guidelines for sulfate levels around the world are shown in Table 1.

TABLE 1.  RECOMMENDED MAXIMUM SULFATE LEVELS

Authority	Sulfate Concentration (mg/L)
USA	500
Canada	1,000
European Union	1,000
South Africa	600
Australia	1,000
World Health Organization (drinking water)	250

From:    Ramachandran, 2012

Many treatment technologies have been developed and refined to remove sulfate from water, including chemical, biological, and physical processes.

Chemical Treatment Technologies

Chemical methods for reducing sulfate concentrations include:

1. Lime precipitation
2. Barium precipitation
3. The CESR process
4. The SAVMIN™ process

The simplest technology for reducing high sulfate concentrations is lime precipitation.  Adding calcium as pebble lime, hydrated lime, or limestone can precipitate calcium sulfate (gypsum) and reduce sulfate concentrations to the solubility limit of 1,500-2,000 mg/L.  Concentrations already below this level will generally be unaffected by lime addition.  Typical equipment requirements for this process are a lime silo, lime slaker, or other reagent feed system, reaction tank, and clarifier.  If sulfate must be further reduced (“polished”), an add-on process such as barium, CESR, or SAVMIN is recommended.

As a polishing step for sulfate removal, barium salts can be added to precipitate barium sulfate, which has a very low solubility in water, with the final sulfate concentration limited only by the amount of barium added and reaction time.  Typical salts used are barium chloride and barium carbonate.  The disadvantage of barium addition is the relatively high chemical cost; a recent price for barium chloride was about $2/lb.

The Cost-Effective Sulfate Removal (CESR) process was originally developed as the Walhalla process in Europe in the 1990s.  A specialized powdered cement (reagent) is added to precipitate ettringite, which is a hydrated calcium aluminum sulfate compound.  The CESR process requires lime addition and a pH of about 11.3 for ettringite formation, and can achieve sulfate concentrations far below the gypsum solubility limit (Reinsel, 2001).  Sulfate concentrations are typically limited only by the amount of reagent added and reaction time.  Disadvantages are the large amount of sludge generated, and the fact that high sodium concentrations inhibit the process.  The CESR reagent costs about $0.40/lb.

The SAVMIN process was developed by MINTEK in South Africa in the 1990s to treat acid mine drainage.  Ettringite is precipitated as in the CESR process, in this case by recycling aluminum hydroxide.  Sulfate levels can be reduced to less than 200 mg/L by this process.  MINTEK has signed an agreement with Veolia South Africa to further develop the SAVMIN process (Ramachandran, 2012).  The first pilot evaluation of the improved SAVMIN process using Veolia’s MULTIFLO™ clarifier was recently undertaken.

Biological Treatment Technologies

If metals are present in the water to be treated, biological treatment has the advantage of being able to remove them along with sulfate via metal sulfide precipitation.  Biological processes for removing sulfate include:

1. The THIOPAQ™ process
2. Other packed bed or fluidized bed reactors
3. Passive treatment
4. In situ treatment

In the THIOPAQ process developed by the PAQUES company (Netherlands), sulfide is produced by contacting the sulfate-containing stream with sulfate-reducing bacteria (SRB) in the presence of a carbon source (electron donor) such as hydrogen gas or acetic acid.  The reaction for hydrogen is:

                SO42- + 4 H2 + SRB à S2- + 4 H2O

Excess sulfide can then be converted to elemental sulfur (So) with aerobic bacteria as follows:

                HS- + ½ O2 + bacteria à So + OH-

The main advantages claimed by this process are:  a) H2S concentrations are low, b) most of the H2S present will be dissolved in water rather than in the gas phase, c) the process can be conducted at ambient temperatures, and d) flow rates can be varied.  The first commercial plant for this process was built in 1992 at the Budel Zinc refinery to remove zinc and sulfate from acid plant blowdown (Ramachandran, 2012).  Numerous other plants are in operation using this technology.

Apex Engineering has designed several relatively small-scale treatment systems for sulfate removal from mine water (Table 2).  The first three are packed bed systems with a continuous carbon source feed (methanol or ethanol), while the last is a passive bioreactor.  We are in the process of designing two more passive bioreactors for construction in 2015.

TABLE 2.  SULFATE REMOVAL SYSTEMS
Location	Client	Year Built	Description
Babbitt, MN	PolyMet Mining	2012	Packed bed 10-gpm system for mining pit lake
Republic, WA	Kinross Gold	2006	Packed bed 50-gpm system for mining-impacted groundwater at closed gold mine
Republic, WA	Kinross Gold	2005	Packed bed 6-gpm system for mining-impacted groundwater near active tailings impoundment
Elko, NV	Veris Gold	2014	Passive 10-gpm system for seepage from rock disposal area at active gold mine

Passive bioreactors or biochemical reactors are another proven technology for sulfate removal.  Biochemical reactors (BCRs) are engineered treatment systems that use an organic substrate to drive microbial and chemical reactions to reduce concentrations of metals, acidity, and sulfate (ITRC, 2013).  BCRs have been used primarily to treat mining-influenced waters over the past two decades.  BCRs may be configured to operate with or without external energy and chemical input, and can often be sustained for months at a time without human intervention (hence the name “passive bioreactors”).  A list of sulfate-reducing BCRs is shown in Table 3.

TABLE 3.  BIOCHEMICAL REACTORS

Site Name	Location	Design Flow (gpm)
West Fork	Missouri	1,200
Golinsky Mine	California	10
Iron King Mine	Arizona	7
Yellow Creek 2B	Pennsylvania	10
Ore Hill Mine	New Hampshire	6
Golden Cross Mine	New Zealand	300
Kendall Mine	Montana	5
Haile Mine	South Carolina	6
Quinsam Mine	British Columbia, Canada	250
Delamar Mine	Idaho	20
Luttrell Repository	Montana	5

According to Mattson (2014), standard bioreactors have a performance advantage over BCRs but at increased capital and O&M cost.  Standard bioreactors such as THIOPAQ or packed bed systems are more efficient and can be better adapted to large-scale applications, according to Mattson.

In situ sulfate reduction (ISSR) is an innovative technology that combines biological sulfate reduction with remediation hydrogeology approaches (Gillow et al., 2014).  A carbon source such as lactate is injected to catalyze sulfate reduction via in situ SRB, with sulfur then sequestered as sulfide minerals and/or elemental sulfur.  ISSR was developed by ARCADIS.  Apex Engineering has incorporated ISSR as a component of the treatment systems for Kinross Gold and Veris Gold (Table 2).

Reported advantages are:  a) many choices for low-cost carbon sources, b) low potential for process disruptions, and c) less effort to operate than pump and treat.  However, challenges include managing the precipitates, managing final water quality, distributing the carbon source in the subsurface, and the possibility of sulfate “rebound” after treatment ceases.  Several options are available for injecting the carbon source. 

ARCADIS’s view on the future outlook for ISSR is that:

• It is a viable technology for specific applications.
• It is important to consider depth, saturated thickness and downgradient receptors.
• Iron addition to control dissolved sulfide should not be necessary.
• Hydraulic performance and biogeochemical parameters should be monitored.
• The technology should be scaled from pilot-scale to intermediate/full-scale.

Physical Treatment Technologies

Physical processes for removing sulfate include:

1. Ion exchange processes such as GYP-CIX and Sulf-IX™
2. Nanofiltration
3. Reverse osmosis

GYP-CIX is a fluidized bed ion exchange process developed in South Africa to remove sulfate from water that is close to gypsum saturation, so it could be used as a polishing step after lime precipitation.  It is the historic predecessor to the Sulf-IX process, which maintains the IX resin in the same vessel to minimize attrition from resin handling.

BioteQ Environmental Technologies of Vancouver has developed the Sulf-IX process to remove sulfate from waters high in hardness and at near gypsum saturation levels.  The Sulf-IX process is designed to selectively remove calcium and sulfate from water to achieve effluent compliance with sulfate discharge limits.  It is a two-stage IX using two resins (one cationic and one anionic) to partially demineralize the feed water.  The cationic and anionic resins are regenerated using sulfuric acid and lime, respectively, to generate nontoxic solid gypsum (the only byproduct of the process).  One significant advantage of Sulf-IX over membrane systems is that it produces no brine solution, providing substantial cost savings on brine disposal via storage or evaporation.  The first commercial plant using this technology has been operating in Arizona since 2011, with a capacity of 600 m3/day (110 gpm).

Nanofiltration (NF) is a membrane process that can be used to remove sulfate and other contaminants.  It operates at higher pressures (higher operating costs) than microfiltration or ultrafiltration, but lower pressures than reverse osmosis (RO).  NF will have a high removal (high rejection) of sulfate because it is a divalent ion, but will have lower rejection of monovalent ions such as nitrate and sodium.  For NF and other membrane processes, sulfate and other contaminants are concentrated in a reject stream, which may comprise between 10 and 40 percent of the original flow.  Disposal or treatment of the reject stream is another consideration.

Reverse osmosis for sulfate removal is generally only considered when monovalent contaminants must also be removed.  Otherwise, NF is more cost-effective for sulfate removal than is RO.

Golder Associates presented a recent paper summarizing sulfate removal treatment processes (Golder, 2014).  Their conclusions include:

• Active biological treatment has never become popular despite extensive research and development.
• Passive treatment has advanced and may be cost-competitive.
• Operating costs for IX are sensitive to reagent prices and reagent utilization efficiency.
• Membrane technologies for sulfate removal below gypsum solubility levels are commercially demonstrated and have achieved acceptance.
• The cost and complexity of advanced sulfate removal projects warrants independent peer review.

Chotila Chamunda Mataji Temple - Gujarat India

History

Jay Mataji

The history of Chamunda Maa is very puranic (old), why people say indian legends and stories are classed as myths is very wrong as substantial proof, history and artefacts have been found.

Maa in chotila are swayambhu, which means she has self manifested and has not  been man made.

 The story is that a holy man had a dream in which he was told by Maa that she was under the earth on Chotilo hill.

He was instructed to dig in a certain spot and Maa would appear there, he did what he was told to do and they found the beautiful Chamunda Maa. At that spot the temple was consecrated and to this day the temple is still there.

In the last decade the temple has been renovated and the darshan hall has been extended the new steps and corrugated sheets above the steps have been provided by the Ambani brothers.

Many people say Chamunda Maa is twinlike or two sisters that is not true, the story is that Kario Bhil was a devotee of Chamunda Maa and was his kuldevi and he had promised Maa that if he begot a child he would make another image of Maa in chotila if his prayer was fulfilled.

Maa chamunda is very dayali and listened to his prayer, over time he forgot about his promise and Maa gave him a test, he was caught stealing by the British raj and sentenced to jail. Why you wonder why a Bhakt of Maa was caught stealing.

Chamunda Maa had given him a shawl that when laid on the ground and sit on it  would transport him into the air, the reason he was given this was to pillage the ships of the british raj that was carrying gold, jewels and coins which they had taken away from indian rajas. He started to carry out Maa's wish and with this treasure he would sell it and feed the poor. One day he was caught due to Maa's lila and taken into jail. Maa appeared to him in a dream and reminded him of his promise.He woke up and apologised to Maa and said he would fulfill the promise, due to difficulty as he was now old Maa completed his promise and she self manifested a secong image of herself in Chotila.

Geography

Chotila is also a small town, in the district Surendranagar. Chotila is a small town having population of around 20,000 people and is a Nagarpalika, Taluka headquarters and Legislative Assembly area. The Mataji temple is situated at the top of the Chotila hill. Mataji temples are mostly located at the top of the hills in India and the reason for this is that if you want to visit the Mata Temple, you will have to undergo some physical strain. Total footsteps were around 366. Now, after renovation,there are around 700 footsteps. Chotila is located on the Rajkot-Ahmedabad National Highway No.8A.It is around 170 km. from Ahmedabad and 60 km from Rajkot. Compare to sea level Chotila is the tallest point in Saurashtra region. The hill is 1,173 feet above sea level

This Chamunda Mataji Temple is Located at Chotila Village. Chotila is very small town come village 50 KM away from Rajkot City. Chotila is on the way from Rajkot to Ahmadabad, National Highway 8 (On NH-8) in Gujarat India.

The story is when Demons Chand and Mund came to conquer Devi Mahakali and in the fight that ensues, the Devi cut their heads and presented these to Maa Ambika, who in turn told Mahakali that will be worshipped as Chamunda Devi. Again Mataji temples are always located at the top of the hills in India and the reason for this is that if you want darshnas of Mataji, you will have to undergo some physical strain.

Chamunda Mataji is the Kuldevi (family Goddess) of most of the Hindus staying in Saurashtra region of Gujarat State in India.

In Chotila Mountain, there about 700 stoned steps up to the top of the hill. These steps were not covered by the shade before about 5 years. However, a good shade and railings now cover the entire walkway thus providing comfort to all the pilgrims. Famous industrialists, Ambani brothers of Reliance industries have donated this covering and the shades on the hill.

Chotila is a small town having population of around 20,000 people and is a taluka head quarter of Rajkot district, Gujarat. The Chamuna Mataji Temple is situated at the top of the Chotila Mountain. Chotila Mountain is around 1250 feet high and is located around 40 miles away from Rajkot, and around 50 miles away from Ahmedabad.

During the navaratri festival, a big havan used to take place on top of the Chotila hill. It is said that after the aarti at chotila hill in the evening everybody comes down the hill and that no one stays there that's what Chamunda Mataji has said. Also people have encountered that there is a lion on the hill or dungar of chotila.

Chotila in Gujarat is “Birth Place of Dimpal Kapadia & Zaverchand Meghani”

Famous Hindi film actress Dimpal Kapadia was born in Chotila Gujarat India. She is elder daughter of Chotila’s Gujarati entrepreneur Chunnibhai Kapadia and his wife Betty. When her daughter twinkle Khanna(now married to famous Hindi film hero Akshay Kumar) visited Ahmedabad some years back, she specially visited Chotila and paid her visit to Chamunda temple on the hill.

Saurashtra’s most celebrated writer, author, poet, journalist, freedom fighter late Zaverchand Meghani was also born here in Chotila Gujarat India. House in Chotila where Zaverchand Meghani born was in neglected condition till recent time, but some people have started to preserve it now. 

Once the arati has been done in the evening no one is allowed to stay in the temple, even the pujaris have to leave the temple.

people have actually seen a very big cobra appear to people who do not follow this command.

Once a man decided he would sleep outside the temple for the night, not realising the command when he woke up the next morning he was at the bottom of the hill.

Maa's lions also stays on the hill that is the reason why there is a large statue of a lion outside the temple as it is also Maa's vahan (vehicle).

In ancient times each shaktipith in gujarat has a lake or talav where you bathe before you visit the temple, the name of the lake for Chamunda Maa is called Bhadarv Nadi.

No one hardly goes there now as ancient customs are slowly being forgotten. 

 At the entrance to Chotilo Hill there is a Mandir where you can have darshan of Maa (a replica of Maa is here), where you can go if you are not able to climb the steps.

If you are able to go to the Mandir at the top of the hill , then you also have to visit the temple at the bottom, otherwise your darshan is not complete. This mandir is at the entrance where you start to see all the shops on either side before you reach the Hill. A third mandir has been built at the bottom of the hill which also has a replica of Maa.

The aarti of Maa is very different no words are spoken the aarti is done with the beating of drums.

The aarti starts of with dhoop being offered to Maa and then aarti is done with lamps (divas).

How to Reach Chotila:

Dharmshala: Yes  

Nearest Hospital: Yes, Civil Hospital, Rajkot  

Best time to visit: July to September and Other Months as well. 

Nearest Railway Station: Rajkot Railway Station  

Nearest Airport: Rajkot, Airport 

Bus Transport: It’s situated on Ahmedabad-Rajkot Main Highway; this place is easily Reachable through Roadways. Local Bus transport is available from Rajkot; Chotila to Rajkot Distance is 50-55 km.

Sewage Treatment technologies - MBR (Membrane Bioreactor), MBBR (Moving Bed Biofilm Reactor), SBR (Sequencing Batch Reactor), SBBR (Sequencing Batch BiofilmReactors )

MBR, MBBR, SBR & SBBR

 Conventional Activated Sludge Process:

Activated sludge plant involves:

1. Aeration tank in presence of microbes
2. Solid-liquid separation followed by Aeration
3. Discharge of clarified effluent
4. Wasting of excess biomass, and
5. Return of remaining biomass to the aeration tank.

In activated sludge process waste water containing organic matter is aerated in an Aeration tank which micro-organisms degrade the soluble organic matter. Part of organic matter is synthesized into new cells and part is oxidized to CO₂ and water to derive energy. In activated sludge systems the new cells formed in the reaction are removed from the liquid stream in the form of a flocculent sludge in settling tanks. A part of this settled biomass, described as activated sludge is returned to the aeration tank and the remaining forms waste or excess sludge sent to Sludge Drying beds.

Conventional Activated Sludge Process Limitations:

•         MLSS values – 3500 ppm

•         Sludge carry over  in the treated water

•         Media filter efficiency max 100 Microns

•         Colloidal Particles – Poor SDI

•         Difficult to maintain consistent treated water quality

•         Odor  in the Treated effluent

•         Upset in system due to inlet variations

•         Large area and huge civil works required

•         Maximum 70 – 80 % of Bio degradation of BOD/COD.

To overcome the above limitations the following new technologies was innovated for better performance in waste water treatment. They are

 

               Sequencing Batch Reactor (SBR)

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Definition:

An SBR operates in a batch mode with aeration and sludge settlement both occurring in the same tank.

All the process like Equalization, Aeration and Sedimentation will take place in a single tank. Sequencing batch reactors operate by a cycle of periods consisting of fill, react, settle, decant, and idle. The Influent will enter the tank through bottomdistribution will contact with Microorganisms and Air was supplied for Micro organisms through  Aerator and the Process of Aeration will take place until complete biodegradation of BOD and the Air blower will stop automatically depend upon the BOD load of the Influent and the same tank will act as Settling tank. The clear liquid from the top of the tank will let out after completes settlement and the Extra Bio mass also was sent out through bottom line. During this clarifying period no liquids should enter or leave the tank to avoid turbulence in the supernatant.

The wasted sludge is pumped to an anaerobic digester or sludge drying bed  to reduce the volume of the sludge to be discarded. The frequency of sludge wasting ranges between once each cycle to once every two to three months depending upon system design.

The major differences between SBR and conventional continuous-flow, activated sludge system is that the SBR tank carries out the functions of equalization aeration and sedimentation in a time sequence rather than in the conventional space sequence of continuous-flow systems.

Advantages:

1.       SBR system can be designed with the ability to treat a wide range of influent volumes whereas the continuous system is based upon a fixed influent flow rate. Thus, there is a degree of flexibility associated with working in a time rather than in a space sequence.

2.      SBRs produce sludges with good settling properties providing the influent wastewater is admitted into the aeration in a controlled manner.

3.      Controls range from a simplified float and timer based system with a PLC to a PC based SCADA system with color graphics using either flow proportional aeration or dissolved oxygen controlled aeration to reduce aeration to reduce energy consumption and enhance the selective pressures for BOD, nutrient removal, and control of filaments

4.      . Working with automated control reduces the number of operator skill and attention requirement.

5.      Lesser Foot prints.

6.      . The duration, oxygen concentration, and mixing in these periods could be altered according to the needs of the particular treatment plant.

Disadvantages:

1.      Appropriate aeration and decanting is essential for the correct operations of these plants.

2.      The aerator should make the oxygen readily available to the microorganisms.

3.      The decanter should avoid the intake of floating matter from the tank.

Sequencing Batch Biofilm Reactors (SBBR)

To optimize the operation of traditional SBR’sand reduce the aeration phase with less HRT, a new technology has been developed which  is called as Sequencing Batch Biofilm Reactor (SBBR), a newly developed System in which intelligent controlling system (ICS) has been  adopted to control the SBBR. Stable performance was achieved in the SBBR at a hydraulic retention time (HRT) of 7 h, at which point the removal efficiencies ofNH3-N, TP and COD reached 99%, 100% and 96%, respectively. When compared with conventional SBR, theSBBR controlled by the ICS reduced the HRT and total aeration time by 56% and 50%, respectively, and achieved better performance in removing the COD. In addition, the optimal carbon nitrogen (COD/N) ratio for the Simultaneous removal of nitrogen and COD in the SBBR was found to be 12.5, and no accumulation of NO3—Nor NO2−-N was detected at this ratio, indicating that efficient simultaneous nitrification and denitrification. (SND) was occurring in the reactor. The SND efficiency reached 98%.

Recently, the sequencing batch biofilm reactor (SBBR) system has attracted a great deal of attention due to its ability to take advantages of both a biofilm reactor and a SBR.

Advantages:

1. SBBR systems showimproved biomass concentration in reactors with corresponding higher specific removal efficiencies, greater volumetric loads, increased process stability toward shock loadings and are capable of covering small areas.

2. SBBR systems canremove nitrogen and phosphorus simultaneously.

3. Presence of an anoxic microzone in the biofilm could result in Simultaneous nitrification and denitrification in the SBBR during the aeration phase.

4.  In such cases, nitrification occurs on the surface of the biofilm, whereas denitrification occurs in the inner layers due to a dissolved oxygen (DO) gradient within the biofilm.

Disadvantages:

1.      Even though we will get good bio degradation of BOD, we will get some Suspended Solids which cannot able to remove by SBBR.

2.      Capital cost is high.

MOVING BED BIO REACTOR (MBBR)

In the MBBR biofilm technology the biofilm grows protected within engineered plastic carriers, which are carefully designed with high internal surface area.   The bio reaction is carried out in controlled environment in this process. The MBBR biofilm technology is based on specially designed plastic biofilm carriers or biocarriers that are suspended and in continuous movement within a tank or reactor of specified volume.  The Bio reactors comprises of a tank, fitted with aeration grid. The bacterial activity needs dissolved oxygen, to synthesize the organic matter. This is supplied by passing air in the form of small bubbles. The air is passed at the bottom of tank, so that complete volume of tank is utilized. Oxygen dissolved in liquid which can now be used by the bacteria. The bacterial population is present on the media, which forms an integral part of the reactor system. The media is made of small plastic elements. Millions of such pieces are kept in the MBBR. The bacteria grow on the plastic media, by using the organic content in the raw sewage and the dissolved oxygen available. Due to constant aeration the media is set in whirling motion, so that continuous mixing takes place. The bacterial layer growth on the media surface increases to a certain extent, and then gets sloughed off after a specific period. This phenomenon is called sloughing. This creates new surface for further bacterial growth. Sloughing takes place only after complete growth and subsequent dyeing – off the bacterial layer.

Diffused aeration involves the introduction of Atmospheric air into the sewage through the submerged diffusers. Part of organic matter is synthesized into new cells and part is oxidized to carbon dioxide and water. The sloughed bio mass must be removed before the treated effluent is taken for downstream treatment. The Sloughed bio mass is drained to sludge drying beds.

Advantages:

1.      It is efficient, compact and easy to operate.

2.      It can be an excellent solution, since it is a standalone process.

Disadvantages:

1.      Continuous monitoring is required.

2.      We may get some dead mass in clear supernatant which increase the filter load.

MEMBRANE BIO REACTOR (MBR)

Definition:

Activated Sludge Process (ASP), an Old technique in waste water treatment is combined with highly efficient membrane filtration to start a sophisticated technique called Membrane Bio Reactor (MBR). Membrane bioreactors (MBRs) combine the use of biological processes and membrane technology to treat wastewater.Within one process unit, a high standard of treatment is achieved, replacing the conventional arrangement of  settling tank and filtration that generally produces what is termed as a tertiary standard effluent. The advent of membranes makes the wastewater treatment easier nowadays. It is an efficient process for maintaining a long solids retention time (SRT) at a relatively short hydraulic retention time (HRT), which is needed for the treatment of waste water.The dependence on disinfection is also reduced, since the membranes with pore openings, generally in the 0.1-0.5µm, range trap a significant proportion of pathogenic organisms. The more common MBR configuration is to have the membrane immersed in the wastewater, although a side stream configuration is also possible, with the wastewater pumped through the membrane module and then returned to the bioreactor. Operating at Mixed liquor suspended solids (MLSS) concentration of up to 12,000 mg/L and a sludge age of 30-60 days

 MBR is favored to all other conventional techniques because the treated water is free from suspended solids and microorganisms, thus making it suitable for reuse. This unique application gives high degradation rates, extremely low sludge production and very compact design.

Advantages:                                                                                       

1. SUPERIOR TREATED WATER QUALITY

1.     Safe rejection of Bio Mass

2.     Enhanced Standard of Hygiene through barrier filtration

3.     Consistent BOD levels of 3-7 ppm

4.     Ultra filtered water free of pathogens.

5.     SDI < 3 achieved consistently

2. PROCESS SUPERIORITY

1. Can  tolerate larger input variations
2. Aeration tank MLSS levels
3. 8000 - 12000 ppm
4. Reduction in aeration tank size
5. Aeration  system can handle higher loads
6. Sludge can be wasted directly to sludge handling equipments.

3. Low SDI in treated water

•          Removes difficult pre treatment for downstream Recycle systems

4. Modular units facilitate easy plant expansion
5. Eliminates filters – No Back wash waste.
6. Disinfection only based on specific requirement