While submerged aerated filter (SAF) systems have been proven effective in ammonia removal, there has been a reluctance traditionally to use them in some quarters, explains Baird.
The energy requirement for delivery of the required high volumes of air has meant that some operators have viewed the method as too costly and baulked especially at applying SAFs to larger schemes.
“There are actually very few papers written on the SAF process and often engineers take information from activated sludge systems and transfer it to SAFs, but the systems are not the same,” insists Baird.
WPL claims its newly launched Hybrid SAF product has unique flow characteristics that promise to overcome the perceived limitations of submerged aerated filters.
Varying the aeration rate affects the movement of neutrally buoyant media, oxygen transfer rates, flow conditions and the way biomass adheres to and shears off surfaces, argues WPL. In turn, this can significantly reduce power consumption per person equivalent treated.
In support of its claim that the evidence against SAFs is at best patchy, WPL has commissioned Portsmouth University PhD student Ashley Lawrence [pictured] to assist on a continuing study at Southern Water’s Petersfield wastewater treatment plant.
Explains Baird: “We are seeking to define the actual performance parameters for SAF treatment in various applications, and at different scales, with the aim of determining precise design criteria for SAF nutrient removal.”
The new SAF technology’s unique characteristics ensure an even and continuous flow of nutrients up through the submerged, moving bed, he explains.
“The slowly circulating media gradually descend due to their increasing specific gravity from hosting growing biomass. Using gravity in this way, opposed to using energy, results in a significant reduction in power consumption, improving overall efficiency and enabling a reduction in site footprint and a deployment of a more compact unit.”
Pump systems too are playing their part in the effective exploitation of water resources, mindful of the fact that supply and reserves will come under increasing demand as global populations and industry expand.
Water treatment manufacturer APATEQ turned to Wanner International’s seal-less pumps for the challenging task of producing effluent water from a contaminated landfill site to drinking water quality.
Contaminated water from one landfill site in Sicily was successfully converted to drinking water quality, providing cost savings and environmental benefits by reducing the high cost for transport and treating of the leachate at an external facility on the Italian mainland.
The pump had to be light and versatile, but also robust and reliable
Natalie Wick, research associate, Bundeswehr University Munich
APATEQ’s Ultrafiltration pre-treatment removes approxi- mately 100% of suspended solids and microorganism from the contaminated water. There is then a post treatment with a three-stage reverse osmosis to treat the UF permeate, which removes the rest of the dissolved salts and other solubles.
Two additionally high pressure reverse osmosis systems will be used to reduce the volume of the first reverse osmosis stage brine flow.
When coping with high concentrations of chloride in the process liquid, the seals and packing in competitor pumps will deteriorate very quickly. Hydra-Cell pumps’ seal-less design reliably handle corrosive liquids to save unplanned downtime and reduce maintenance costs.
Hydra-Cell’s seal-less pump design ensures that the T100 can reliably handle liquids containing particles from 0.1 to 800 microns, and more abrasives with less wear than on axial piston or plunger pumps, says the company.
Watson-Marlow Fluid Technology Group (WMFTG) meanwhile has been applying its expertise to the specifically environmental challenges presented by plastics and their negative effect on water quality.
Germany’s PLASTRAT research project, co-ordinated by Bundeswehr University Munich and supported by the Federal Ministry of Education and Research, is focusing on the often overlooked issue of microplastics in inland waters – an issue often overshadowed by the greater emphasis on ocean waste.
“One of the initial primary tasks of PLASTRAT was to develop a uniform, comparable method for taking samples at wastewater treatment plants”, says Dr Christian Schaum, Professor for Sanitary Engineering and Waste Management at the university. Samples must be taken at timed intervals to compensate for fluctuations throughout the day and ensure proper comparisons. The procedure must also exclude the potential for samples to become contaminated by other plastic particles.
Working at the Fellach wastewater treatment plant in Holzkirchen, near Munich, researchers developed a sampling procedure that takes these criteria into consideration. Over 24 hours, a pump feeds the water from which samples are to be taken into a holding tank. The water in this 1,000 litre tank is then stirred to promote homogenisation and create a mixed sample.
“The sample is subsequently passed through a multi-level cascade of filters with pore sizes of 50 and 500 μm to concentrate the microplastic particles,” explains research associate Natalie Wick, a member of the project team, with filtration residues analysed to see how much microplastic remains.
“Samples had to be taken at the sand trap outlet, as well as the outlet from the secondary treatment area, at different wastewater treatment plants,” explains Wick. “Therefore, the pump had to be light and versatile, but also robust and reliable.”
As well as maintaining high levels of precision, sample water had to be pumped into tanks that were several metres higher than water level.
The pump employed also required programmable interval dispensing functions and to be able to draw in water autonomously. And it was essential that the samples were not contaminated with other plastic.
Silicone or Teflon were the only materials not found in any significant quantities in the wastewater samples and therefore the only plastics that could be used.
The choice was a WMFTG 323Dz tube pump that offers a closed peristaltic pumping system, with no impellers, seals or valves in the area through which the medium is fed. As well as preventing contamination, they are self-priming and effectively prevent damage that would be caused by running dry while powerful suction handles any difference in height.
It feeds 1,000 litres of water into the sample tank over 24 hours. The pump extracts five litres of water in each of the 200 sampling cycles, with automatic transportation taking approximately 2.5 minutes, with the system programmed for a set number of dispensing processes with a specific quantity at set time intervals.
After more than two years it works reliably and efficiently when taking samples in different situations, says Wick.
Grad times ahead
With a socially distanced induction and immediate working from home for some, Yorkshire Water welcomed 17 new colleagues on to its graduate scheme recently.
University graduates join the business on a two-year development programme. In their first year, recruits undergo four placements in different areas of the business, then choose a specialism and role to complete their final year. After the programme, they are supported with finding permanent roles.
Chief people officer Jenni Morris, said: “The graduate scheme is a fantastic way to bring new talent into the business. By gaining experience of lots of different departments they get to really understand the company and identify areas where they can add strength.”
Picture: Justine Pearson attends the project management graduate programme