Commercial Wastewater Treatment

Electrolytic Process

What is M.R.T.? - The new generation in water treatment.

Abstract

"Electrochemical techniques are among the most widely used current applications in environmental protection and waste treatment. And their potential is even brighter. Broadly defined, electrochemistry is the study of those chemical and physical events that result in the flow of electrons (electricity), essentially through oxidation and reduction reactions. Although there is a tremendous interest in using electrochemistry to develop new and greener ways of manufacturing and using chemical products, a far broader need is to address the waste and pollution already produced (and continuing to be produced) by the non green process of the past and present.

Not only is electrochemistry a cheap and efficient way of dealing with some of the most common extant pollutants, it is also showing itself to be a greener alternative to several other forms of cleanup now available. The benefits of taking an electrochemical approach to waste removal are many. According to Krishnan and Ibanez [1997], they include environmental compatibility, versatility, energy efficiency, safety, selectivity and amenability to automation, and cost effectiveness.

Perhaps, among these, versatility is the most notable. Because electrochemistry can generate (whether through oxidation or reduction) neutral or charged species at will, whether inorganic or organic, and can deal with solid, liquid, or gaseous pollutants, it only takes a chemical engineer's imagination to develop new methods of use.

Waste product cleanup can occur through direct electrolysis of the pollutants to non-toxic forms, indirect methods using additional reagents, or through hybrid electro physical separation methods such as flotation or coagulation. The method is also versatile because a plethora of reactor and electrode materials shapes and configurations can be utilised and volumes of fluid from micro-litres to millions of litres can be treated (Rajeshwar and Ibanez, 1997)".
Courtesy of 2002 American Chemical Society

The M.R.T. Technology is a breakthrough in the capability
to provide a sustainable efficient current density
at a very low electrical energy requirement.

This technology will automatically apply different current densities
to changing wastewater organic loadings.

Technology Process Description

Coagulation and Flocculation

Coagulation and flocculation are traditional methods of adding chemicals to treat polluted waters and separate solids from liquids. This traditional method creates a sludge volume at a ratio of 2 -3 times the actual sludge volume of the pollutants separated and increase the salinity of the treated liquid with the addition of ions from the chemicals. That is; the Total Dissolved Salts [TDS] rises significantly and will cause an adverse affect on the environment where the treated effluent is discharged to.

The electrolytic process of treating wastewater applies an electric charge to the wastewater through an electrolytic cell immersed in the wastewater containing electrolytes. Electrolytes are ionic compounds that conduct electricity in water based solutions and these ionic compounds have negative and positive charges.

Electrolysis of water has had its moments in history but there have been only a small number of companies in the world that have advanced the technology and each has its own concept of the technology. The main failures have been passivation of cell plates, short life of cell plates and sustainable current density efficiency to provide economical energy costs. The process is a mature, proven process in Europe and the United States of America

M.R.T. has spent the last fourteen years developing and field testing the M.R.T. electrolytic process of treating wastewater and the engineering design necessary for a sustainable, economic treatment process. The development process, field testing and engineering has resulted in the M.R.T. Re- Engineered Electro Organic Destruction [EOD] Methodology as a non chemical continuous pre-treatment process of various wastewater streams.

The anode/cathode material is a dimensionally stabilised anode [DSA] manufactured overseas with a manufacturer's specification for maximum current density and capable of active duty in acid or base solutions. The M.R.T. Reactors are designed for maximum current efficiency under most conditions and operating at twenty percent of the maximum current density specified by the manufacturer. Current efficiency can be adjusted to suit high or low level pollutants in the wastewater. Passivation does not occur.

Sacrificial anodes are part of the reactor design and are simple and economical to replace. The rate of dissolution is dependent on the current density of the reactor but cannot exceed the maximum of design. The electro-coagulation of wastewater by electrolysis is therefore created with the formation of a hydroxide combining with electrochemically charged anions and cations coagulating to form a floc suitable for separation from the liquid.

Electro-flocculation

The charged ions react with soluble and insoluble pollutants in the wastewater forming a floc that slowly increases in size by contact with ions of the opposite charge. The electrochemical reactions precipitate pollutants that are in a soluble state, e.g. chemical residues, and these precipitated salts form a floc. In a quiescent state the floc will generally settle to the base of a treatment tank and requires removal together with liquid, and then the sludge de-watered in another step. In a state where the liquid is flowing the floc is less defined and more difficult to separate from the liquid.

It is for this reason that most other electrolytic treatment plants are based on a batch process rather than a continuous process and the volume treatment capabilities are reduced.

Field testing and in situ demonstrations has proven that a continuous process is economically viable and very efficient. This wide experience has determined retention times in various polluted wastewaters and this data has been used in the engineering design of the M.R.T. Treatment Tanks.

The M.R.T. Treatment Tank design provides for a large floc formation in a circumvent cycle with excellent flotation capabilities.

The M.R.T. electrolytic process generates active oxygen ions, chlorine gas, hypochlorite, ozone gas and other halogens creating oxidation-reduction reactions within the liquid to reduce and eliminate bacteria, pathogens, micro-organisms, soluble BOD and nutrients. The process precipitates some soluble salts. The M.R.T. electrolytic reactors are capable of effective current density in TDS solutions as low as 100ppm.

Electro-flotation

An electrolytic reactor, when placed in a solution containing ions and with an electric charge passing between the reactor plates, generates an enormous volume of extremely fine gas bubbles with a bubble size generally in the range 25um – 30um. The cathode produces hydrogen gas bubbles and the anode produces oxygen gas bubbles. The volume of gas bubbles is understood to be in the millions per litre of liquid.

It is well known that bubble sizes can affect the flotation efficiency. Small bubbles are desired because they have large specific surface area, which is very important for achieving effective flotation of particles from wastewater.

Dissolved Air Flotation or DAF systems are well known and the technology is based on the release of compressed air into a liquid via diffusers with air bubbles forming, rising to the surface and carrying solids to the surface. In a DAF system the air bubble size is generally in the range 50um-70um. They rise rapidly and expand in size during the rise and although considered an effective solid separation method, the rapid rise and larger bubble size miss a lot of the fine suspended solids and these fines stay in the liquid. Downstream filtration has a heavier loading due to these fines with the consequences of frequent backwashing cycles and loss of water.

Electro-flotation occurs with microscopic size gas bubbles generated in the electrolytic process slowly rising to the surface and not expanding at the same rate as larger bubbles. The slow rise allows for more contact time for the bubble to contact the floc and the floc attached to the fine bubble to attract more floc. The larger floc mass rises to the surface of the liquid to form a sludge blanket. During the separation process the surface sludge blanket thickens with a layer of aerated mass on top.

The M.R.T. Treatment Tanks are designed for the hydraulic flow of the liquid to move towards the treated effluent outlet by passing through barriers which prevent untreated liquid from passing straight through the treatment process. This hydraulic flow carries the surface sludge blanket forward to a sludge collection system which reduces the volume of liquid contained in the sludge.

M.R.T. Re-Engineered Electro Organic Destruction [EOD]

The former sections describe the various process reactions that occur in electro-coagulation, electro-flocculation and electro-flotation. In many cases organic bearing wastewater is treated using biological systems, [activated sludge, bio-reactors and trickling filters are some]. In some cases, due to the nature of the organics, for example toxicity or the time required for the biological system to breakdown the organic [s], biological systems may not be effective or economical.

Wastewaters may be taken offsite for disposal or activated carbon used to adsorb the organic. In each case the result is high operating costs.

The M.R.T. EOD Process is a re-engineered electrolytic technology for the non chemical, non biological, treatment of organic contaminants in wastewater streams. The EOD process involves oxidising organic compounds both directly at the surface of the catalytic electrodes and indirectly by the oxidation of chemicals existing in the wastewater.

The result is the precipitation of soluble organics and chemical residues which are entrapped in the electro-coagulation/electro-flocculation/electro-flotation process and transported to the surface of the liquid forming a sludge blanket.

The M.R.T. Re-Engineered EOD Process is a Primary/Secondary treatment of the wastewater to a state where significant removal of organic pollutants and chemical residues have been achieved and on application to various types of common filtration systems, the filtration systems are able to operate in a sustainable condition to provide a high quality reusable water supply.

The final water quality can be tailored to suit the use application including, Reservoir , Class A or Potable. The latter requiring the need for a disinfection process to be included at the end of the process stream.

Other wastewater streams for effective re-use treatment include;

  • Car & Truck Wash Down Facilities
  • Treatment of effluent from sewage treatment works
  • Treatment of irrigation channel water to process water quality
  • Treatment of drainage channel water to irrigation water quality
  • Treatment of industrial wastewater for free oil and soluble oil separation
  • Treatment of grey wastewater to irrigation quality water, dust suppression, wash down or toilet flushing
  • Mining leachate water and acid mine water
  • Mineral Removal Technology
  • New generation waste water treatment

Current Primary Wastewater Treatment Process

Current Secondary Wastewater Treatment Process

The M.R.T. EC / EF Wastewater Treatment Process

CASE STUDIES

Case Study No.1

Juice Plant, Riverina, NSW

Sludge blanket forming during an in situ demonstration at a juice plant, Leeton NSW

A juice plant located at Leeton processes fruits to fruit juices creating about 500 kilolitres of wastewater per day which is discharged directly to the sewage infrastructure.

The discharged wastewater is high in BOD5, Total Suspended Solids and pH 10-11. The Leeton Shire Council has concerns about the ongoing effect of this wastewater stream on their sewage treatment plant. The Company pays a high surcharge for discharging into the sewer.

The Leeton Shire Council organised for AMS to attend the site with the M.R.T. Mobile Demonstration Plant and carry out a demonstration of the M.R.T. process to determine the effectiveness of the BOD and TSS reduction.

The demonstration plant enables water samples to be taken at the end of the EC/EF phase and the final filtration stage.

Raw untreated wastewater was pumped from the site holding tanks to the demonstration plant with the raw wastewater held in retention for a pre-determined period of time. At the expiration of the retention period, raw wastewater flowed into the treatment tank at a simulated flow rate with conditioned effluent from the EOD process flowing into a storage tank, then pumped through the filtration modules for a final filtrate.

Representatives from the Leeton Shire were present took samples of the raw wastewater. effluent discharging from the M.R.T. EC/EF tank and the final filtrate. The Council transported those samples to a local laboratory for analysis. Table1. sets out these results, plus the percentage reductions achieved.

Case Study No. 2

Wastewater from a tobacco company Wet Scrubber, Sydney, NSW

The tobacco company derives wastewater from the Wet Scrubber in the process of washing tobacco leaf. Despite installing various treatment systems to enable re-use of the wastewater, a solution of colour and odour removal has not been achieved.

Wet Scrubber wastewater was processed through the M.R.T. mobile demonstration plant and achieved a high quality re-use final filtrate with literally no colour and no odour. Table 2 sets out the results of analytical tests carried out by Nalco Laboratories for the Tobacco Company.

Table 2 BOD TDS TOC pH Conductivity Turbidity True Colour
Sample Mg/L Mg/L Mg/L Unit uS/cm NTU PtCo
               
Raw 7500 860 5539 5.0 1172 1900 300
EC/EF 6000 630 4751 5.4 1151 65 110
Filtrate 900 460 724 7.5 936 6.8 2

Case Study No.3

Cheese Manufacturer – Leeton, NSW

A company with dairy product processing plants at Leeton and Albury creates a large daily flow of wastewater containing oil & grease, suspended solids, BOD5, nitrogen, phosphorus with the values in excess of the local WTP target limits.

At the request of the Leeton Shire Council AMS conducted an onsite demonstration of the M.R.T.™ EOD process at the Leeton Plant of the cheese manufacturer in December 2006.

Raw wastewater was extracted from the final point of discharge into the sewer and processed through the M.R.T. ™Demonstration Unit. During the process, representatives of the Leeton Shire Council took samples of the raw wastewater, treated effluent after the M.R.T.™ electro-flotation stage and the final filtrate and transported the samples to a local laboratory for analysis. Table 3. sets out the results of the analysis.

Albury City Council –
Target Limits for discharge to sewer – as mg/L

BOD TSS Oil & Grease Nitrogen Total Phosphorus
2500 800 200 100 20
M.R.T Comparison
2410 56 136 47 24

 

Features, Advantages and Benefits of the M.R.T. EOD Wastewater Treatment System.

M.R.T. EOD Features

  • Modular design allows for scale to suit small – medium and high volumes, suitable for daily flows from 10,000 litres to Mega litres
  • Small land footprint required
  • Fabricated polypropylene treatment tanks, stainless steel on request
  • Advanced design of Reactors and Reactor Power Controllers
  • Fully automatic on start up with Delta PLC control
  • Easily installed – no major infrastructure requirements
  • Vacuum Sludge Collection System
  • High quality filtration systems with advanced hollow fibre Membrane technology
  • 50% less sludge than chemical systems – non toxic chemical residues precipitated – suitable for land fill disposal

M.R.T. EOD Advantages

  • Water Re-use – 98% of the total wastewater flow recovered for re-use
  • Disinfects and purifies
  • Taste and odour removal
  • Automatically controlled
  • No impact on local environment
  • Non chemical treatment – no hazardous chemicals to store
  • No added chemicals – safe work place conditions
  • Sustainable filtration
  • Tertiary quality filtrate
  • 50% reduction in sludge volume compared to chemical treatment
  • Modular engineered design allows for increase in plant capacity

M.R.T. EOD Benefits

  • Reduced water purchase cost
  • Nil or reduced discharge fees to local infrastructure
  • Treatment Plant fully maintained at no additional cost
  • Low operating cost – electricity power only
  • Corporate image – Company seen as a genuine provider of water resource conservation and management of environmental risks

Mineral Removal Technology (PAT 2009-901-280)

MEAT PROCESSING – DAIRY – FEEDLOT – PIGGERY and
POULTRY INDUSTRIES

M.R.T. has developed a combined process of anaerobic, biological, electrolysis and filtration to provide a sustainable supply of recycled water suitable for process water, wash down water, cooling towers and irrigation at these facilities.

Stage 1. Primary Treatment

Raw sewage, wash down water and backwash concentrate are delivered to a primary screen for removal of large size matter. The screened wastewater then flows to septic tanks to provide a minimum of three days retention for anaerobic primary treatment. The primary treatment stage contains odour within the tanks.

Stage 2. Secondary Treatment

The primary treated effluent gravity discharges to a distribution tank for distribution into the NuTreat Biological Filter.

The NuTreat Biological Filter comprises a special media where the biomass builds deep into the media bed to provide a natural aerobic condition for the biological digestion of soluble and insoluble pollutants. The primary treated effluent is applied within the top layer via a distribution manifold and permeates down through the media and transferred by a collection manifold to a pump well for recirculation and transfer to the next stage. The recirculation rate ratio is calculated according to the wastewater being treated. The recirculation process includes transfer of treated effluent back to the primary stage to aid the de-nitrification process.

The effluent quality from the NuTreat Biological Filter is generally 20/30 with total nitrogen <30mg/l and significant reduction in fats/grease and nutrients content.

There is no odour from the NuTreat Biological Filter.

Stage 3. Tertiary Treatment

Secondary treated effluent is pumped from the re-circulating pump well to the M.R.T. Treatment Tank for tertiary treatment by electro-oxidation /electro-coagulation/electro-flocculation/electro-floatation. The effluent from this process is completely disinfected with further reduction in BOD, TSS, Nutrients and Total N. The effluent is generally low in turbidity, colour and no smell. The sludge is removed from the surface by hydraulic flow and transferred to a holding tank for offsite removal or return to the primary tanks.

Stage 4. Tertiary Filtration

The clarified M.R.T. treated effluent is transferred to the selected filtration process. This process will include hollow fibre ultra filtration for process water requirements and mixed media/carbon filtration for irrigation and wash down requirements. The filtration is automatically controlled for backwash and cleaning procedures. The backwash waters discharge to the sludge holding tank.

The entire process ensures no odour or gas external pollution and provides a constant high grade recycled water quality.

Typical process flow chart for the M.R.T. treatment for recycling waste for many applications such as Meat processing, Dairy, Feedlot, Piggery & Poultry industries

*MRT is Patent 2009-901-280

Contact Us

  • Postal Address:
  • PO Box 1160
  • Wagga Wagga NSW 2650 Australia
  • Location:
  • 111 Biroomba lane
  • Wagga Wagga NSW 2650 Australia
  • Phone: 02 6925 8555
  • Fax: 02 6925 8588
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For information on the treatment of other water types, see Coolabah Water, here!