February 19, 2018

Quit wasting time in wastewater filtration

By Cytiva

Tips from Susan - a quest to discover time savings in wastewater treatment.


Susan takes pride in the work she does each day. After all, without her expertise in the lab, the plants and animals that live in and around her community’s waterways could suffer.

Susan is a Lab Manager at a wastewater treatment plant working in a specialized laboratory that tests wastewater samples, or effluent, which originates from industrial plants or domestic sewage. The sample filtration tests performed by her team are required to meet federal regulatory standards at wastewater treatment plants like hers, as well as at contract labs.

To give herself a chance at success, Susan takes a robust approach to understanding where her team must spend their time and how it can be optimized. Susan’s team uses gravimetric assessment to measure the Total Suspended Solids (TSS) in each sample, a common practice in effluent testing. In the US, TSS is determined by using Method 2540 C, D, and E, the standard filtration method approved by the Environmental Protection Agency (EPA). The method passes a sample of water through a glass microfiber filter and measures (a) the solid residue left on the filter (suspended solids), (b) the solid residue from the filter that incinerates at high temperatures (volatile solids), and (c) the solids residue present after evaporating the water that passed through the filter (dissolved solids). Because of the critical nature of the filter in this process, the method states that it be binder free glass fiber and be prepared according to specific steps prior to use. Specifically, it should be rinsed three times, then dried and weighed until a constant weight is obtained. In testing for Volatile Suspended Solids (VSS), the filter must also be ignited in a furnace at 550°C.

The steps in this method, and others like it, mean that Susan and her team always seem to have more tasks to do - a real challenge given that her budget was cut last year and she is constantly being asked to do more work with fewer resources.  This has led to a significant backlog and concerns with accuracy in Susan’s lab.  For example, in suspended solids testing, Susan found that her team spends an average of 168 minutes preparing each filter to meet the required standards for approved filtration. While pre-rinsing the filters takes just under a minute, drying the wet filter at 105° C for one hour actually takes a total of 77 minutes once the filter is transferred from pre-rinsing because of the time required to pre-heat the oven. Preheating the furnace to the to 550 C° required for volatiles testing is also more time consuming than Susan thought -- it takes 35 minutes! Add in the 15 minutes it takes to ignite the filter a second time, as well as a total of 40 minutes to cool down the filters and weigh them twice, and Susan’s head was spinning.

With so many samples to get through and such little time to spare, her team operates under stressful circumstances seven days a week. And with seven steps in the filtration process, there is too much room for human error. She is worried about her lab’s ability to keep her community’s waterways safe and flowing with clean water, so she has begun exploring ways to free up more time in her lab.

Having understood her problem, Susan began looking for solutions. That’s where the Whatman 934-AH RTU (ready-to-use) filters by Cytiva comes into play. These filters have been pre-treated to various degrees in accordance with Standard Method 2540, saving time and costs compared to the filter Susan had been using. In fact, she calculated that the pre-treatment could save her team up to 392 hours per week.  And with fewer steps in the filtration process, Susan’s team would have less room for human error, increasing their confidence in their analyses. Susan also likes that each pretreated filter comes in an aluminum pan, with the filter weight clearly noted, and each pan has its own unique barcode that can be used to find documentation of the filter weight on the Cytiva website. Each box of 934-AH RTU filters also has a barcode that can be used to download the weights of all filters from that box to support regulatory record keeping.

By implementing the 934-AH RTU into their workflow, Susan anticipates her team will be able to process a high volume of difficult samples with more accuracy and free up precious time to tackle other vital tasks around the lab. Most importantly, Susan is eager to accomplish her main goal of ensuring the purity of the waterways for her community.


Try our Whatman Filter Selector App to find out if you are using the most appropriate filtration solution for your samples. To discuss any challenges you are facing, please contact Cytiva's Scientific Support.