PUMPS, VALVES & ACTUATORS FEATURE PUMPS TAKE ON PLASTIC CONTAMINATION PROBLEM


A tube pump from Watson-Marlow Fluid Technology Group is playing an important role in wastewater sampling to assess the problem of microplastics in inland waters


A


research project looking at the problem of microplastics in inland


waters has been using a 323Dz tube pump from Watson-Marlow Fluid Technology Group (WMFTG) to ensure sampling is practical, reliable and consistent. The compact 300 series pump not only operates with the required accuracy and reliability, but eliminates the potential for plastic contaminants to cause inaccurate measurement results. Although shocking images have


highlighted the problem of plastic waste in oceans, the issue of microplastics in inland waters has gone relatively unnoticed. However, increasing quantities of plastic particles that are 5mm or less in size are now commonplace in lakes and rivers. Private households are among the main culprits, mainly due to particles detaching from textiles during washing, and particles from cosmetics. The PLASTRAT research project, co-


ordinated by Bundeswehr University Munich and supported by the German Federal Ministry of Education and Research (BMBF), aims to assess the size and scale of the problem. “One of the initial primary tasks of


PLASTRAT was to develop a uniform, comparable method for taking samples at wastewater treatment plants,” explained Univ.-Prof. Dr Christian Schaum, Professor for Sanitary Engineering and Waste


Management at Bundeswehr University Munich. Samples must be taken at timed intervals to compensate for fluctuations throughout the day and ensure proper comparisons. The procedure must prevent samples becoming 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,” explained Natalie Wick, a member of the project team. “The filtration residues are analysed to see how much microplastic remains.” One of challenges was selecting the


optimum pump for sampling. “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,” said Wick. “Therefore, the pump had to be light and versatile,


AERATION AND PUMPING CONTROLS POTATO PROCESSING ODOURS


Following the successful installation two years ago of Landia Chopper Pumps and a Landia Aeration System, MSE Systems is set to install a further three units from Landia for a UK supplier of potatoes. During an upgrade to the customer’s potato processing factory, MSE Systems found that the addition of


a high-efficiency Dissolved Air Flotation (DAF) plant would improve the activated sludge process by reducing oxygen demand. To ensure that the plant could meet future needs and remain fully compliant with Environment Agency discharge consent, a new chemical addition system was introduced to remove suspended solids, free emulsified oils, grease and elevated residual phosphorus. For odour control, an 11kW Landia AirJet system was installed to mix, aerate and control odours of screened


potato effluent in a balance tank. In addition, two submersible Landia Chopper Pumps were brought in to pump screened potato effluent from a 4.5m deep pit (500m away), with an additional 4m lift. Andy Neal, design manager at MSE Systems, said “For a new packing line, two submersible Landia


Chopper Pumps will pump potato effluent, whilst a Landia Jet Mix system will mix organic sludge (dissolved solids 3-5%) in a 60m3


tank.” MSE Systems ensured that the initial installation proceeded with the minimal amount of disruption, in


order for their customer to reopen on schedule. Despite the tight time frame, the new wastewater treatment plant was delivered by MSE Systems ahead of deadline and within budget. www.landia.co.uk


/ PROCESS&CONTROL www.msesystems.co.uk


Sampling is performed automatically at programmed intervals


but also robust and reliable.” Alongside high levels of precision, the


sample water sometimes had to be pumped into tanks that were several metres higher than the water level. Furthermore, the pump would need programmable interval dispensing functions and be able to draw in water autonomously. "As we wanted to investigate the presence of plastic particles in the water, it was important that the samples were not contaminated with other plastic,” said Wick. To exclude this possibility, the only


plastics which could be used were silicone or Teflon. These materials were not found in any significant quantities in the wastewater samples and could therefore be excluded from the analysis process. It quickly became clear that only a tube


pump could satisfy this long list of requirements. Thanks to its closed peristaltic pumping system, only the tube comes into contact with the medium, in this case the water sample. Unlike other pump types, a tube pump has no impellers, seals or valves in the area through which the medium is fed. This design not only prevents contamination, but it's unobstructed flow path also means that blockages are extremely unlikely. Tube pumps are the best solution for


continuous autonomous sampling at intervals over 24 hours because they are self-priming and effectively prevent damage that would be caused by running dry. Moreover, powerful suction handles any difference in height between the sampling point and the holding tank. "We've already had positive experiences


with Watson-Marlow tube pumps in our laboratories,” reported Professor Schaum. This led to the selection of a Watson- Marlow 300 series cased tube pump, which would be used to feed 1,000 litres of water into the sample tank over 24 hours. The pump extracts 5 litres of water in each of the 200 sampling cycles, with automatic transportation taking approximately 2.5 minutes. The pump can be easily programmed to perform a set number of dispensing processes with a specific quantity at set time intervals. Thanks to the flip-top pumphead, the


tube, or even the entire pumphead, can be swapped out in a matter of minutes. In this project, a silicone tube supplied by Watson-Marlow was used to prevent samples from being contaminated by plastic particles. The pump has already been running for


more than two years and “works reliably and efficiently when taking numerous samples in very many different situations”, concluded Wick.


WMFTG www.wmftg.com


PROCESS & CONTROL | NOVEMBER 2020 17


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