Latest technological developments focus on harnessing nature and reducing odour, writes Margo Cole.
The drive to improve water quality has seen an enormous growth in the scale of sewage and waste water treatment works. But the promoters of a new technology claim their system can dramatically reduce the required capacity of treatment works and cut out odour at sewage works.
The technology was initially developed in Spain three years ago, and is now being promoted in the UK by the Building Research Establishment (BRE), which has formed an alliance with Spanish firm Nimasco.
Known as the Eco-Bio Process, the technology works by accelerating natural biodegradation.
The earth is endowed with an in-built cleaning mechanism through the activities of microorganisms that work together to break down pollutants on land and in water. For example, the oceans have 20 to 25 families of microbes that break down the polymeric chains in hydrocarbons - such as oil - to reduce them to carbon dioxide and water.
Micro-organisms like these exist for the degradation of most pollutants, including sewage, agricultural wastes and most types of organic waste. However, the key limitation with this natural process is time: for example, the complete natural degradation of solid sewage, takes up to six months.
The Eco-Bio Process works by enhancing and accelerating these natural microbial activities by introducing nutrients, vitamins and bio-stimulants - referred to as 'micronutrients' - to catalyse the performance of the natural micro-organisms.
As a result, according to the Nimasco-BRE alliance, foul odours in sewage can be completely eliminated within three to six hours.
All Eco-Bio ingredients are organic, and are produced from naturally occurring plant extracts - including 'Dakarin', the active ingredient at the heart of the process. Karim Esmail, the BRE's director of technology, explains: 'The Eco-Bio Process basically accelerates nature by catalysing local, indigenous micro-organisms with allnatural micronutrients.'
This differs from most biological processes used in the environmental industry today which rely on introducing foreign bacteria or enzymes that have been externally conditioned or genetically engineered into an ecosystem in order to degrade contaminants. Esmail emphasises: 'The Eco-Bio Process works purely on accelerating local indigenous micro-organisms, which is a vital factor with respect to environmental safety and ecosystem conservation.'
The mix of nutrients depends on the application - so different ingredients would be required for hydrocarbon degradation and wastewater treatment, for example. But all products are supplied ready mixed in powder and liquid form. The products can be dosed manually or automatically.
Esmail says the Eco-Bio Process has many uses in waste water and sewage treatment, but the two most obvious are process enhancement and odour elimination. 'One of the key issues at the moment is the capacity of works, ' he explains.
'This system could be introduced as a natural enhancer to boost the biological reactions to a level that permits a higher throughput in an existing plant. ' Effluent coming out of the Eco-Bio Process would be significantly cleaner than that currently entering sewage works, and would require less treatment time - although Esmail refutes suggestions that the process could be used to replace conventional treatment altogether.
Great effort and expense goes into trying to reduce odour at treatment works. The two options available are either to completely cover areas storing and treating effluent, or to apply tertiary treatment processes such as ozonation.
Esmail claims the Eco-Bio Process can eliminate odour by degrading and/or suppressing the materials that cause odour, for example hydrogen sulphide gas, and sulphur bearing organic compounds called mercaptans.
The process was trialled at a sewage treatment works in southern Spain with a capacity of 35,000m 3per day. The trial took place during summer 2001, and involved installing a hydrogen sulphide detector in the sewage reception tank and setting up a panel of four people to make a qualitative record of the amount of odour.
Eco-Bio products were continuously added to the raw sewage pumping station 4km from the plant and to the sewage reception tank for a month.
At the end of the month the dosage was stopped completely, but the readings continued.
The average hydrogen sulphide concentration during the period when Eco-Bio dosage was applied was 3.57 ppm - compared with 18.6 ppm three weeks after dosing stopped. At the same time, the odour levels reported by the panel reduced dramatically on introduction of the dosage. At the main pumping station and entrance tank, odour levels had previously been rated as 'strong' or 'very strong'.
They reduced to close to zero at the pumping station with only a mild smell at the entrance tank within days of the Eco-Bio products being introduced. Both levels rose again sharply once dosing stopped.
Since the Spanish trial Anglian Water has put the system through its paces to remove blockages and get rid of odour on a 10km long pipeline carrying wastewater through the Lincolnshire countryside. Odour disappeared altogether within a day, leading the company to instigate another trial at a sewage treatment works.
The Nimasco-BRE jv has also had enquiries from Yorkshire Water, which is exploring the possibility of installing the system as pre-treatment to increase capacity at an existing works.