To help Yorkshire Water meet tighter discharge consents at Balby WwTW near Doncaster, Vexamus Water has installed the UK's first tertiary sand filter with a 7m2 filter area.

To help Yorkshire Water meet tighter discharge consents at Balby WWTW near Doncaster, Vexamus Water has installed the UK's first tertiary sand filter with a 7m2 filter area. Offering the same continuous filter process as smaller units, but with a significantly reduced footprint of the filter package, the DS7000 is part of the renowned DynaSand range, which is distributed exclusively in the UK by Vexamus Water. Serving an equivalent population of 20,000, the Balby WwTW consent was reduced from 30 mg/l to 20 mg/l of suspended solids (new consent: 10:20 BOD:SS).

As well as reducing washwater requirements, DynaSand also improves the process output and greatly simplifies the system.

Handling high suspended solids without the need for pre-treatment, this tertiary sand filter benefits from lower capital costs and eliminates the need for washwater storage, collection or backwash pumps.

Three new bersonInLine systems join three existing systems to meet the increased wastewater treatment demands at the Flat Creek Water Reclamation Facility in Georgia USA.

The Flat Creek Water Reclamation Facility (WRF) in Gainesville, Georgia, USA, has chosen Berson UV disinfection equipment to meet the facility's increased wastewater treatment demands. Three new bersonInLine systems join three existing systems to meet the plant's expanded capacity, treating over 1,875 m3/hour of wastewater for discharge into a local lake. The closed pipe, medium pressure systems, installed by the Berson American sister company Aquionics Inc, provide high efficiency disinfection with the added benefits of online transmittance monitoring and advanced controls.

Flat Creek WRF originally installed Berson equipment in 2001, with three bersonInLine systems treating approximately 1,250 m3/hour of wastewater (80% industrial, 20% low level commercial and residential).

With the area's growth the plant's capacity increased, and with increased capacity came more stringent discharge permit limits.

The new permit issued for a 1,875 m3/hour capacity with a faecal coliform limit of 23 colonies per 100 ml sample was a significant change from its previous limit of 200 colonies per 100 ml sample.

The City of Gainesville and Berson engineers determined that additional UV systems arranged in series would achieve the level of disinfection required by the new permit.

A total of six bersonInLine systems now treat effluent at the plant.

Berson closed pipe systems use high output medium pressure UV technology to deliver a high dose of UV disinfection which destroys microorganisms using fewer and smaller lamps than comparable low pressure systems.

The closed chambers are compatible with both gravity fed and pumped applications, providing low maintenance disinfection with minimal headloss.

The closed pipe design was an important feature for the City of Gainesville.

When first selecting UV equipment for the Flat Creek WRF, representatives from the City's Public Utilities Department visited several neighbouring facilities and examined a range of open and closed pipe systems from various manufacturers.

'The excessive man hours required to keep an open channel unit clean was a large factor in choosing the Berson closed pipe system initially,' said the plant manager.

Ease of handling was another feature in Berson's favour.

Rather than handling an entire bank of lamps at a time, the bersonInLine single lamps may be changed quickly and easily by plant personnel.

To further reduce maintenance, the chambers are equipped with an automatic cleaning mechanism to keep lamp sleeves free of organic deposits.

The new systems feature the new Berson UVTronic microprocessor controls and transmittance monitor, providing real time transmittance values that allow for dose pacing of the UV system.

The control unit records up to 12 months operational data for record keeping and analysis and generates fault alarms to aid in the diagnosis of performance problems.

The controller can also be fitted with a modem connection to perform remote diagnostics on the system for fast troubleshooting with minimal service interruption.

For wastewater disinfection before mixing with a polymer for sludge decantation and dewatering, a municipality in Denmark has installed a Hanovia medium pressure UV disinfection system.

To ensure wastewater is effectively disinfected before being mixed with a polymer for subsequent sludge decantation (separation) and dewatering, the Stege Kommune municipality in Denmark has installed a Hanovia medium pressure UV disinfection system. The wastewater/polymer mixture decants the sludge into two phases as part of the dewatering process. The sludge, which is subsequently used for agricultural purposes, is disinfected by heat treatment prior to decantation, so the wastewater/polymer mixture needs to be completely free from bacteria, viruses and other microbial contaminants.

The treated wastewater is also used to clean the sludge decanter at the end of the process.

To ensure optimum performance, the Hanovia UV system is fitted with a hand-operated wiper.

This keeps the quartz sleeve surrounding the UV lamp free from fouling and means UV output is always at its maximum.

The system has a capacity of 10.8m3/hr.

UV is widely used to remove harmful pathogens from drinking water and wastewater.

It is a completely clean technology which does not rely on the use of chemicals and leaves no unwanted residues or by-products.

Recent research suggests medium pressure UV is more effective at permanently destroying micro-organisms than the alternative method - low pressure UV.

In the research, the two methods were compared and micro-organisms were shown to repair themselves after exposure to low pressure UV, but not medium pressure UV.

This research has serious implications for operators of water and wastewater treatment plant and is one of the reasons why more and more of them are switching to medium pressure UV technology.

Many WWTP can experience both low and high wastewater temperatures at various times of the year.

The efficiency of low pressure lamps is known to fall off significantly at these extremes, and can even fall to zero when the incoming wastewater temperature is below 5C.

Medium pressure lamps are unaffected by these temperature ranges - they always start up easily, show no change in UV output and do not age any quicker than lamps used at 'normal' temperatures.

According to the Hanovia Danish distributor, the Stege Kommune is very satisfied with the performance of the Hanovia system, which was chosen for its quality and fast pay-back time.

As concern for the environment grows, so does the need for efficient handling of both industrial and domestic effluent: ABS Pumps have provided equipment for an 1100m long pump-driven sea outfall.

As concern for the environment grows, so does the need for efficient handling of both industrial and domestic effluent. Selecting the right equipment in order to avoid damaging the environment through problems caused by blockages, spills or leaks is of paramount importance. So when a major US-owned industrial company based in Ayrshire decided, in consultation with SEPA, to invest GBP3 million in replacing its existing 50m long gravity fed sea discharge pipe with a 1100m long pump-driven sea outfall, the contractor turned to global solutions provider ABS Pumps for two material-specific pumps that would suit the task in hand.

The project carried out by the company, due to concerns over the possible deposition of solids on the local shoreline, decided the situation could be avoided by installing an extended outfall, buried initially under the beach and subsequently the sea bed.

The contractor managing the mechanical/electrical systems for the project was Glasgow-based Ferrier Pumps, a specialist in this field.

The chief concern in this particular application was the nature of the media being pumped.

Although the resultant solution was very much diluted, the client decided that it would invest the additional monies involved on the basis of longevity and reliability, and hence it specified that the pump hydraulics and pedestals were to be manufactured from Duplex stainless steel.

'ABS is one of our main suppliers for submersible pumps,' explains the Ferrier Pumps director PJ McFeeley.

'Although we contacted a couple of other potential suppliers only ABS could meet our material requirements'.

Other requirements included: suitability for fixed guide rail installation; solids handling capability; suitability for inverter speed control; duty requirement of 213 litres/sec at 12.76m per pump.

The use of inverters was so that, as far as practical, the discharge rate met the inflow rate to maintain a constant level in the pump sump.

The ABS pumps offered to meet this specification were two 37kW, Z6300-C2-2908 models.

They were installed in late 2003 and have been operating trouble-free ever since on an alternating duty/standby regime.

A central control station, constructed by Ferrier, monitors the status of the pumps and flow rates, which can be observed and adjusted.

The cost of cleaning up after a mishap can be expensive, but careful selection and installation of pumps and equipment can help ensure that plant integrity always meets the standards required.

In the system installed by Ferrier, an alarm will signal in the event of a blockage and effluent will be diverted back down the old gravity fed outfall.

'Since installation the ABS pumps have worked fine,' concludes Mr McFeeley.

'We have a maintenance contract with the client and the first service on the pumps took place in August.

Siemens have supplied SWW with a reliable, accurate and most importantly MCERTS approved flow monitoring system for measuring discharge flow from treatment works to meet EA requirements

When South West Water found it necessary to comply with the Environment Agency's strict standards for discharge flow from treatment works, they turned to Siemens Process Instrumentation and Analytics for a flow monitoring system that was reliable, accurate and most importantly MCERTS approved. South West Water in the UK provides water and sewerage services to customers in Devon, Cornwall and parts of Dorset and Somerset - a large region with a population of 1.5 million residents. This figure increases to more than 2 million during summer tourist season, and as a result there is a wide variation in water system demand and flows.

In recent years, the company has upgraded treatment works, pumping stations, and sewers to meet tighter standards set by the Environment Agency (EA).

The EA has developed a monitoring and certification standard for inspection and production of quality monitoring data and operator self-monitoring known as MCERTS.

Regulations strictly limit discharge flows from treatment works, and require water companies to measure and record the volume of effluent flow from works that have consent to treat in excess of 50 cubic metres a day with an uncertainty of no more than +/-8%.

Where the storm overflow setting can be adjusted, the flow to treatment must be measured and recorded during periods when excess flow is diverted to storm capacity holding tanks.

South West Water needed a reliable, accurate method to measure and document flows at its various sites to meet these regulatory reporting requirements.

For this reason, a flow monitoring plan was implemented, covering 226 sites.

The programme was implemented in five phases by installation contractor May Gurney.

The company selected the Siemens HydroRanger 200 ultrasonic instruments because of their accuracy, reputation for reliability, and because they are MCERTS, Class 1, approved.

This certification assures users that the instruments have passed a rigorous set of lab and field tests conducted over three months by Sira, the independent product certification body appointed by the EA.

MCERTS certification means a product meets EA, national and international performance standards.

In fact, the Siemens HydroRanger 200 controller and Siemens OCM III open channel meter are the first flow instruments certified by the EA.

Echomax transducers (sensors) are located on flumes, weirs and channels to continuously monitor water level.

They provide data to the HydroRanger 200 controllers, which calculate flow and feed the information into a Programmable Logic Controller (PLC).

The PLC formats the required data, which is relayed to the Central Data Archive in Exeter, via telemetry.

The Modbus protocol built-in to the HydroRanger may also be used to communicate instantaneous values of flow.

'The implementation used both open channel and closed conduit flow measurement techniques,' said Dave Curtis, Systems Engineer (SCADA Engineering Systems) with South West Water, 'Once several sites had been commissioned, it was possible to create and refine a generic template and then only site-specific parameters needed to be modified.

We are very impressed with the performance of the instrumentation and the support from the Siemens team.

The flow monitoring plan made South West Water fully compliant with the Environment Agency requirements for self-monitoring of effluent flow.

The Siemens instruments are MCERTS certified so their readings are readily accepted by the EA.

The flow data is also useful for on-going asset management, demand analysis and future planning.

Siemens instrumentation equipment provided significant benefit to the project,' says Gary Jones, Project Manager with May Gurney.

A tough Freshwater Fisheries Directive undertaking imposed new ammonia consent standards at Esher Sewage Treatment Works, solved by a Black and Veatch and Costain project completed well within budget.

The Trident Alliance of Black and Veatch and Costain has enabled Thames Water to achieve a tough Freshwater Fisheries Directive undertaking that imposed new ammonia consent standards at Esher sewage treatment Works. Significantly, Black and Veatch and Costain delivered a first-class solution to its client's needs at a total project cost of less than GBP5M - compared to an original estimate of GBP7M. Bringing major environmental enhancements to the Surrey area, one of the main innovations that resulted in large cost savings on design and construction was the introduction of a combined pumping station and two-stage anoxic zone within a single glass-coated steel tank.

'I really admire the beauty of the finished project.

We also accomplished the project below control cost, which is another bonus.

Black and Veatch and Costain must be congratulated on the completion of a very successful contract,' said Ann Weston, Thames Water Project Manager at Esher.

The complex commissioning phase of the project required detailed planning by the entire project team at the commissioning workshops.

These brought about the conversion of Esher STW from two separate process streams, filter and crude ditch, into a single settled sewage ditch stream, with clearly defined routes and processes for the sludge flows.

At the workshops, the interdependency of each item to be commissioned was analysed to determine the correct commissioning sequence.

Contingency plans were also discussed in the event of any process area failing.

The construction team also worked more than 50,000 hours with zero reportable accidents.

Black and Veatch was highly innovative in its methods of construction, including the use of hydro-demolition, instead of using traditional hand-held heavy breakers, which can lead to hand arm vibration syndrome.

'Thames Water Operations are very pleased with the result as they now have a plant that is within the quality consent and working well, allowing them to continue meeting the needs of local residents in a safe, reliable and cost-effective manner,' said Chris Scott, Project Director for Black and Veatch.

To prevent microbial contamination, the Talschaft Entlebuch waste water treatment plant in central Switzerland has installed a medium pressure, closed-pipe UV disinfection system from Berson.

To prevent microbial contamination of the Kleine Emme river, the Talschaft Entlebuch waste water treatment plant (WWTP) in central Switzerland has installed a medium pressure, closed-pipe UV disinfection system from Berson. The Kleine Emme river is popular with bathers in the summer months, but local residents had become increasingly concerned about poor water quality. This came to a head in 2002 when a number of bathers said they became ill after swimming in the river.

It was suspected that the wastewater outflow from the WWTP was causing microbiological contamination of the water, but no direct link was ever confirmed.

However, the operators of the plant decided that discharges should be disinfected as a precautionary measure.

After considering several options, medium pressure UV disinfection was chosen as the most suitable method.

UV is a clean technology that kills all water-borne pathogens, including Cryptosporidium, without resorting to chemicals such as chlorine.

Berson medium pressure, closed-pipe UV systems are compact and can usually be installed within existing pipework.

The only regular maintenance required is replacing the UV lamps after approximately 8000 operational hours, a simple procedure that can easily be carried out by on-site staff.

The UV system at Talschaft Entlebuch was installed in 2004 and is the first installation of its kind in Switzerland.

It has a capacity of 306m3/hr and is expected to operate during the summer months when bathers use the river.

Based in the Netherlands, Berson UV-techniek is a world leader in closed-pipe UV technology for a wide range of applications, including wastewater and drinking water treatment, dechlorination, ozone removal and TOC reduction.

The company has over 30 years' experience in the design, development, manufacture and distribution of UV systems worldwide.

After practical trials, the innovative Bauxsol technology has been shown to offer a viable and economic treatment solution for phosphate removal in municipal and industrial wastewater treatment works.

Following a six-month independent trial by the UK Water Research Council (WRc), the innovative Virotec Bauxsol technology has been shown to offer a viable and economic treatment solution for phosphate removal in municipal and industrial wastewater treatment works. European General Manager at Virotec, Simon Tillotson, said 'We are very excited about the trial outcome. The WRc trial has shown Bauxsol in pellet form to be a viable passive treatment alternative to chemical dosing for phosphorous removal.

Our solution is based on treatment by simply passing wastewaters through the pellets in our Virofilter system, a straightforward process that can operate unattended without the need for control of dosing rates, and all the associated manning, health and safety issues.

It is particularly viable for remote and small-scale sewage treatment works that need a stand alone, reliable and sustainable phosphorous removal process'.

Virotec has developed a range of patented products for removal of phosphate and metals from wastewater streams and groundwater supplies, and for fixing metals in soils and solid wastes.

Simon Tillotson explained, 'Our range of Bauxsol products are produced from the neutralisation and conversion of caustic red mud, a 'waste' product from alumina refining.

We are taking the abundant supply of red mud and turning it into a valuable enhanced product with exceptional contaminant removal properties'.

Bauxsol works by forming strong ionic bonds with phosphate and metal ions in water or soil.

For the metal ions captured, these are immobilised into a non-leachable and non-bioavailable solid residue.

For phosphates, their removal occurs via ionic and precipitation reactions and the phosphates are held in a slow release and bio-available form.

It is estimated that 50 - 80 million metric tons of red mud is produced globally every year.

Virotec recognised the beneficial properties of this resource and developed and patented their ground-breaking neutralisation and conversion process for transforming the red mud into a valuable product.

Simon Tillotson said 'Bauxsol can be applied as a powder or slurry for direct addition to contaminated waters or soils.

It can also be produced in pellet form for use as granular media, or manufactured into larger blocks.

The extremely high porosity of our pelletised product means that on certain applications we can direct the process flow straight through the solid medium'.

The Virotec phosphate removal solution is to install a simple flow-through Virofilter immediately prior to effluent discharge.

This provides a buffering capacity and allows for variations in hydraulic flow and phosphate concentration.

Upstream chemical dosing is not required, and there is the added benefit of reduced sludge production and lower waste disposal costs.

The system easily meets phosphate discharge consents at less than 2 mg/l (as P) and allows trace metal removal and polishing, as well as providing a substrate for promoting biological activity and additional BOD reduction.

The Virofilter can be installed in horizontal or vertical flow beds, or in a trickling filter type arrangement.

For maximum flexibility, beds are installed in a duty and standby configuration with Virofilter streams operating in parallel or in series dependant on the phosphorous removal rate required.

The longevity of Bauxsol in the Virofilter depends on residence time, influent phosphorous concentration and flow rate.

For example, the likely lifetime for an influent of 6 mg/l (as P) is at least 3 years.

The production and use of Bauxsol is a sustainable process creating multiple reusable and recyclable products from an initial environmental problem.

As pellets would still have metal removal capacity following application in phosphate removal, the enriched phosphate pellets could be reused for heavy metal removal such as in acid mine water treatment.

Alternatively, pellets used for iron removal could be reused for phosphate removal.

In the WRc trial, two beds containing Bauxsol pellet media were operated in a horizontal flow reed bed configuration at residence times varying between 4 and 12 hours.

The work demonstrated that up to 85% phosphate removal could be achieved meeting consents of less than 1 or 2 mg/l (as P).

On trial completion the phosphate removal capacity of the Bauxsol media had exceeded 7g P/kg media without any sign that the pellets were close to exhaustion.

However longer term lab-scale trials have demonstrated that Bauxsol can remove at least 12g P/kg.

Following thorough evaluation, the Environment Agency has awarded Hach Lange a framework agreement to supply wastewater analysis (COD) test reagents and associated services for a period of four years.

Following a thorough evaluation project, the Environment Agency has awarded Hach Lange a framework agreement to supply wastewater analysis (COD) test reagents and associated services for a period of four years. Commenting on the award, Robert Rand, Team Leader at The National Laboratory Service says 'The NLS provides an analytical service to the Environment Agency which requires consistently high standards of accuracy. Hach Lange was selected, based on our assessment of analytical performance, price, quality, and environmental impact'.

Laboratory Sales Manager for Hach Lange Mathew Dillon expressed his delight with the award, adding 'We now supply the EA and ten of the main eleven Water Companies with COD tubes and associated instruments.

The quality and reliability of our DR2800 spectrophotometer, heating block and COD reagents means that customers can rely on the correct reading every time.

The test is extremely simple to perform and it incorporates several unique features designed to substantially eliminate human error'.

COD stands for Chemical Oxygen Demand.

It is a measure of organic pollution in wastewater, and is the most frequently mentioned parameter in European legislation.

The Hach COD test follows the ISO 15705 standard method exactly, with all reagents supplied ready-to-use, in precisely the correct amounts in a small cuvette.

To perform a test, users simply add a water sample to a cuvette and leave it in a heater for 2 hours.

At the end of this period the intensity of colour in the solution is directly related to the COD value in the sample, and can be measured quickly and easily.

Hach Lange claims that its COD analytical instrumentation and associated reagents almost completely dominate the UK market and feedback from some of the company's major customers is given below.

Bob Capron from United Utilities (Wastewater Manager) says 'The laboratory at United Utilities has recently, after carrying out extensive trials involving all major COD suppliers, awarded Hach Lange a three year contract to supply 120,000 COD tubes per year.

The contract has been running since October 2004 and during this time the service in terms of quality, reliability, delivery and removal of used tubes has been excellent.

Hach Lange staff involved in the contract have been extremely helpful at all times'.

Mark Boldy from Anglian Water (Chemistry Manager) adds 'The Anglian Water Services laboratories have used the Lange COD tubes and spectrophotometers for the last eight years.

The main reasons for initial and continued use are the reliability and reproducibility of the product, enabling Anglian Water to meet the requirements of our regulators and customers with respect to COD analysis.

Hach Lange takes responsibility for the safe disposal/recycling of the used tubes and we have been very pleased with the level of service.' In addition, Graham Coe from Thames Water (Laboratory Manager) says 'Thames Water has used the COD test system from Hach Lange for the past 9 years, during this time we have found it both reliable, reproducible and cost effective for the analysis of COD within waste waters and trade effluents.

It passed our validation criteria and the Urban Wastewater Directive and has been audited by both the EA and UKAS.

We have not encountered any problems with either deliveries or the removal of spent tubes or the Hach Lange calibration and repair service.'

It is well known that bacteria and other micro-organisms contain enzymes that can repair UV-damaged DNA, a process known as 'reactivation'.

It is well known that bacteria and other micro-organisms contain enzymes that can repair UV-damaged DNA, a process known as 'reactivation'. Some of these enzymes need visible light to perform the repairs ('photo-reactivation'), while others can do so without light (known as 'dark repair'). Photo-reactivation is generally quicker than dark repair, but both of these phenomena pose obvious problems for operators of UV disinfection plant.

Recent research on the process, however, has produced interesting new developments.

When comparing photo-reactivation of E.coli DNA after exposure to UV wavelengths emitted by low and medium pressure lamps, independent researchers have shown that the DNA underwent extensive repair following exposure to UV from low pressure UV lamps, but virtually none following exposure to UV from medium pressure lamps.

The researchers concluded that it was the broad UV output of medium pressure lamps, between 185-400nm, that has this desirable effect.

By emitting UV over a wide range of the UV spectrum, medium pressure lamps appear to damage other intracellular molecules, such as enzymes, in addition to DNA.

It is this damage which seems to permanently inactivate the cell DNA repair mechanisms.

Low pressure UV lamps, on the other hand, produce only a single UV peak at 254nm which only affects DNA.

These preliminary results have to be considered seriously by operators of low pressure UV disinfection systems.

If, following exposure to low pressure UV lamps, micro-organisms are capable of recovering, users and operators need to seriously consider upgrading to medium pressure technology.

By providing permanent microbial deactivation, medium pressure UV offers peace of mind, something low pressure UV does not do.

Applications affected by these findings are wide-ranging and include municipal drinking water, bottled water, rinse or wash water in the food industries, wastewater and effluent, fisheries and swimming pools.

The analysis of the COD value in waste and surface waters is one of the most expressing to determine the degree of pollution of the water.

The analysis of the COD value in waste and surface waters is one of the most expressing to determine the degree of pollution of the water. COD stands for Chemical Oxygen Demand and reflects the total quantity of oxidisable components, whether it is carbon (C) and hydrogen (H) from hydrocarbons, nitrogen (N) from proteins, or sulphur (S) and phosphorous (P) from detergents. Unlike the TOC value (Total Organic Carbon), only expressing the carbon coming from pollutants, the COD value is expressing the lot.

The very principle of COD analysis is the depletion of an oxidiser given to the sample and being consumed by the pollutants, whereas the TOC analysis is based on the generation of CO2 caused by the oxidation of the organic components, usually being detected by an infra-red detector.

There are several oxidisers, all strong enough to oxidise the various components there may be in the aqueous sample.

However not many are stable enough to suite a quantitative chemical analysis as most of the oxidisers not only oxidise the pollutant but also themselves, which obviously would lead to false results in the analysis.

The most stable oxidiser is a solution of potassium bichromate (K2Cr2O7) mixed with sulphuric acid.

Hence the reason this oxidiser has been chosen to base the normalised method on (DIN 38409-44, EPA 410.4).

This is the true COD test and is used in all wastewater testing.

Another very suitable oxidiser is a solution of potassium permanganate (KMnO4).

This is often used in the potable water industry and with water authorities to determine 'COD'.

The permanganate test is quite suitable also to be used in wastewater and has the advantage not to release a harmful waste (Cr3+ and Cr2O7), although the quantities are minute.

To execute these tests a small amount of sample is mixed with an excess of oxidiser solution and boiled for a certain time.

According to the normalised test this time should be 2 hours but maybe set shorter when the sample allows, eg for waste waters with a predictable quickly oxidisable component (like sugar) can be set to a short oxidation time (like 15 min).

Sometimes it is recommended to add catalyst (Ag+), for example in cases to oxidise the 'hardy's' such as aliphatic and aromatic hydrocarbons.

In the case where chloride is present in the sample (which will get oxidised to chlorine and is not considered as COD) it should be immobilised with mercury or it should measured and be deducted in the final COD result calculation.

The latter is preferred since the release of mercury is not wanted; (mind there are also good and simple ways to retrieve mercury by an absorption cartridge which can be disposed of in an environmentally acceptable way).

This oxidation step in the determination is also called the digestion.

The next step in the determination is the detection.

The detection is done by the analysis of the remainder of the oxidiser (either the bichromate or the permanganate).

There are 2 methods of analysing this remainder: titration or colorimetric, of which the first one is referred to in the normalised method because it is the most accurate one.

The colorimetric method requires less hardware and is attractive from an investment point of view.

In the case of bichromate: Titration: The digested solution is transferred to a titration vessel and titrated with a solution of ferrous (Fe2+) against a Platinum electrode.

That is from a precision pump (burette) the ferrous solution is slowly added to the digested solution causing the ferrous to be oxidised instantaneously by the remainder of the bichromate till the potential shift at the electrode tells when all bichromate has been taken out by the ferrous.

The COD value may be calculated then from the difference of the originally added quantity of bichromate and the remainder which is determined by the quantity of the added ferrous till titration endpoint.

Colorimetric: The digested solution is transferred to a colorimetric cell in which the density of the green colour of the chromium ion (Cr3+) is being measured; (the bichromate gets reduced to chromium in the oxidation process).

The measurement is done against a previously stored calibration being a series of chromium solutions with a different concentration.

In the case of permanganate: Titration: The digested solution is transferred to a titration vessel and titrated with a solution of oxalic acid against a Platinum electrode.

Colorimetric: The digested solution is transferred to a colorimetric cell in which the optical density of the purple colour of the permanganate ion (MnO72-) is being measured.

Another strong oxidiser is so called OH radicals.

These radicals maybe generated by either ozone or by an electrode (from a suitable reagent).

The attractive part using ozone, as an oxidiser is it can be generated from air.

A major drawback is that the OH radicals are very short lived (in the order of a few minutes only) and thus only the easy to oxidise components are being measured.

The 'nasty's' are being oxidised only partly.

This makes this method only suitable in those cases where a single polluting component varies in concentration.

In the cases a wide array of pollutants is present in the sample this method will show very inconsistent results showing no correlation with the normalised method.

In those cases one likes to observe the trend of (mainly hydrocarbon) pollutants in the water sample, it is also possible to make use of the approved spectro-photometric method DIN 38404.

By this method all components having absorption ability at 254 nm will be measured.

Like the method just mentioned before this method has similar drawbacks, but Analyzers based on it are not expensive to buy or to maintain.

Any of the mentioned methodologies, except the one using the OH radicals, may be applied with the ADI process Analyser 2040, the most versatile On-line Analyser on the market today.

Whether you choose the bichromate or the permanganate method, the titration detection or the colorimetric, the 2040 is able to run the analysis with optimal precision.

On top of that it features the ability to incorporate 2 more analyses such as ammonia or nitrate or phosphate or others and a virtually unlimited number of physical parameters such as optical density (UV, VIS, turbidity), pH, conductivity, Oxygen, ORP, and many more! Where others need a full array of all kinds of different analysers Applikon can do with just one maybe two.

New service launched as Emerson analysis predicts only 20% of UK water company effluent discharge sites will be on course to confidently pass the MCERTS 5 year re-certification tests.

Emerson Process Management has announced a new MCERTS Health Check service to assist UK water companies in complying with discharge consents. The service will enable dischargers to assess their sites prior to the required five-year re-certification, enabling them to avoid time-intensive and costly last-minute preparations or failures. The launch comes as analysis conducted by the Emerson Mobrey Service (which has provided legislative and technological consultancy to UK water companies for more than ten years) shows a significant number of sites would fail an inspection.

Under the 'MCERTS; Self-Monitoring of Effluent Flow' guidelines, consent holders (processors who have been granted consent to discharge by the Environment Agency) are required to have their sites certified every five years by a qualified MCERTS Inspector.

Inspections review site configuration, flow structures and instrumentation to ensure that they meet the required standards - specifically that there is appropriate measurement and recording of instantaneous and cumulative daily flows.

'In the lead up to the Environment Agency March 2005 deadline for all sites to have achieved certification, water companies invested millions ensuring the right technology and processes were in place,' explains Paul Cherry, Flow Specialist and MCERTS inspector, in the Emerson Process Management Mobrey Service operation.

'A number of previous AMP2 installations could now fail an MCERTS inspection due to a variety of reasons - altered site process configuration, incorrect sizing, lack of adherence to maintenance procedures for example.

As a result, water companies may be un-prepared for what in some cases is a fast-approaching re-certification programme'.

The Emerson Mobrey Service is offering water companies the opportunity to have an MCERTS Inspector 'spot check' any number of their sites, providing consultancy on any problem areas and advice as to what needs to be done, at the least possible cost, to ensure re-certification is achieved.

Cherry concludes: 'The aim is to promote and encourage on-going maintenance and a continual review of procedures so that accurate and appropriate flow measurement becomes inherent within the organisation.'

xThe latest addition to the Alert range from Applikon Analytical is the new nickel analyser for use in monitoring waste waters. Designed for reliability and minimal operator attendance, the Alert analyser is perfect for waste water and process applications. The analyser uses the unique Differential Absorbance Colorimetry (DAC) methodology to prevent background sample colour and solids adversely affecting the analysis.

The analysis is capable of determining nickel down to 0.003mg/l with a maximum calibrated range of 3mg/l.

The running costs are kept to a minimum by low reagent use, typically less than 1ml per analysis, and minimal consumables.

Annual attendance for planned maintenance is usually carried out on an annual basis.

Applikon Analytical BV is part of the Metrohm group of companies and is represented exclusively in the UK by Metrohm.

In addition to the sale of analysers, Metrohm UK provide a full customer service including spares, training and service contracts.

Severn Trent Services, a global leader in water and wastewater treatment solutions, will present at Aquatech the latest developments in Tertiary Treatment and Disinfection Technologies

Severn Trent Services, a global leader in water and wastewater treatment solutions, invites you to visit us at Aquatech to review the latest developments in Tertiary Treatment and Disinfection Technologies at the Aquastage presentations. Firstly on Wednesday, 27th September (1400hr), Water Treatment Aquastage will present 'Tertiary treatment of wastewater - the legislative requirement and technology options'. Numerous European Union Directives have been introduced to enforce strict standards for the treatment of wastewater parameters.The Urban Wastewater Treatment Directive (UWWTD) has enforced mandatory secondary treatment of wastewater and has tightened the permitted concentration values (PCV) for the removal of ammonia, nitrogen and phosphorus.

This presentation will give an overview of current wastewater treatment directives and the range of technical solutions available to meet the legislative requirements.

Then, on Thursday, 28th September (1400hr), at the Water Treatment Aquastage, the presentation will be: 'Disinfection Technology - Finding the right solution for the task'.

This Aquastage presentation will discuss the requirement for safe and reliable disinfection systems, the latest technology that can be used to minimise health, safety and environmental risk and other considerations when assessing the variety of systems available.

With a wide array of water disinfection equipment and technologies, providing the right solution for industrial and municipal applications is simple.

From traditional disinfection equipment and technologies such as gas chlorination to alternative technologies such as on-site sodium hypochlorite generation, Severn Trent Services provides disinfection systems to meet and exceed the needs of our clients.