WET News

12 WET NEWS OCTOBER 2014 The Phragmifiltre system planned to replace the conventional, biological filter works at Hulland Ward will have two stages, The first will filter and dewater raw water solids on the bed's surface. The second stage vertical flow beds provide additional BOD reduction and nitrification of ammonia composts sludge on site, and therefore no tanker costs (opex) and no road- ways (capex) are required. Phragmifiltre also provides wildlife habitats that conven- tional sewage treatment works do not. Conventional sewage treatment works are hazardous areas and can be vulnerable to vandalism, they need security fencing around the whole site, again meaning further capital expenditure. Phragmifiltre requires only security fencing around a few chambers for safety. Conventional sewage treat- ment works require weekly operator visits, unlike the Phragmifiltre sites that require monthly visits (opex). Totex option Phragmifiltre constructed wet- lands are an ideal replacement for ageing sewage treatment works and an environmentally attractive, low totex option for new developments. There is potential for this technology to be aligned with other intensive reed bed treat- ment technologies such as Forced Bed Aeration to enhance treatment capabilities further if required. Severn Trent Water is leading the UK in its use of new tech- nologies for water treatment and the Hulland Ward site will be a show piece site for this new-to-Britain technology. Hulland Ward has the space on site to allow phased installa- tion of the reed beds, says Chris Wainwright, project manager at ARM. Severn Trent purchased additional land to allow the beds to be installed alongside the existing treatment works. Once the beds are up and running, typically between eight and 12 weeks depending on the weather to get the bug popula- tion established, a percentage of the flow will be diverted. When the full flow is running the existing works will be demolished. This is a full scale works, not a trial, and none of the existing works will be used again. Work started on site in July and is expected to be completed by March 2015. In France similar reed bed systems are running in the warm south as well as much colder Alpine regions. The UK, climate- wise, is in the middle but sys- tems are operating in wetter con- ditions more typical of the UK. The Hulland Ward site has thrown up some challenges mainly because the existing works and structures have to be retained until last the reed bed is installed and consent given for the full flow to be diverted. Access to the reed beds is restricted to one side where a new installation would allow access all round. Enthusiasm for this new site is shared by Severn Trent's con- tractor, MWH. "This is a small site but there is huge potential for this technology," says Mark Slatcher, project manager at MWH. "A lot of water companies are looking at different ways of doing things, and should this be successful, Severn Trent will clearly be looking to do more," he says. Reed beds have been around for a good while, used for ter- tiary treatment, but this will do primary and secondary treatment. On this site, MWH is the interface between Severn Trent and ARM, which is stalling the reed beds, maintaining consent during the commissioning phases. This is similar to a traditional reed bed with two to three weeks for the primary phases and about 16 weeks for the second- ary phases, Slatcher says. It is weather dependent with colder weather potentially delaying commissioning. Phased project The small site complicates works slightly, he says. "It is a phased project and we have got to demolish part of the old works to facilitate part of the new build. The old primary tank and part of the old inlet need to be demol- ished in order to complete the third reed bed." He says: "It a small site, tight for space, and we have to squeeze onto the existing land ownership the reed beds that have a large footprint." At Hullard Ward the inlet from the village to the works is reasonably flat so the site will retain some pumps to provide sufficient head necessary to get the dispersion on the primary "A lot of water companies are looking at different ways of doing things should this be successful, Severn Trent will clearly be looking to do more." Mark Slatcher, project manager, MWH ONSITE PRIMARY TREATMENT "Using constructed wetlands as a primary treatment resource is a first in the UK but it is proven technology. Once it is fully established we will also be able to demolish part of the old sewage works making for a more attractive landscape." Dan Cunliffe, programme manager, Severn Trent. reed bed. There are capex and totex advantages using wetland reed beds. Conventional sewage treatment works generate sludges that have to be taken from small rural works to larger facilities for treatment but as Phragmifiltre does not generate sludges there are no tankering costs meaning no extensive, tanker compliant internal roadways. Natural habitat Tori Sellers, director at ARM, says: "The introduction of Phragmifiltre signifies a major change in thinking towards a natural and sustainable alterna- tive for sewage treatment in the UK. "In the past constructed wet- lands have generally been used as a tertiary treatment to polish effluent prior to discharge. Phragmifiltre has added a new dimension to constructed wet- land technology and Severn Trent Water is once again lead- ing the way when it comes har- nessing the benefits of natural wastewater treatment systems." Beds are up and running in eight to 12 weeks depending on the weather to get the bug population established In France similar reed bed systems are running in the warm south as well as much colder Alpine regions A growing need to meet strin- gent discharge consents was just one of the reasons Severn Trent Water chose the Phragmifiltre system, says Dan Cunliffe, pro- gramme manager at the water company. "We have been planning the improvements at Hulland Ward for some time as it is part of our plans to improve land and water environments in the Eccles- bourne Valley," Cunliffe says. He adds: "Following exten- sive research we went to France to see the Phragmifiltre full treatment system in action and we were impressed with its results. Not only does it provide a cost-effective and sustainable solution, the creation of a natu- ral habitat was favoured by the local community." Cunliffe says: "Using con- structed wetlands as a primary treatment resource is a first in the UK but it is proven technol- ogy. Once it is fully established we will also be able to demolish part of the old sewage works making for a more attractive landscape." n

• Cover