Customer Case: 200 QJB Submersible Mixers for a Russian Municipal Wastewater Treatment Plant A Russian environmental engineering contractor responsible for upgrading a municipal wastewater treatment plant selected Quzhou Zhongyi Chemicals Co., Ltd. (brand ZY) to supply 200 QJB submersible mixers for its aeration and sludge tanks. This case study explains the client's operating problem, the technical selection process and the results achieved after commissioning. Customer Profile CustomerEnvironmental engineering contractor, Russian Federation Project typeMunicipal wastewater treatment plant upgrade ApplicationAeration basins, anoxic tanks and sludge holding tanks Equipment supplied200 pcs QJB submersible mixers, 2.2 kW – 10 kW Power supply380V / 50Hz / 3 phase DeliveryTwo 40HQ containers, China–Europe rail corridor The Challenge The plant serves a mixed residential and industrial district where wastewater load fluctuates sharply between seasons and where winter temperatures fall well below freezing. The contractor's original mixers, sourced from a European brand, had reached the end of their service life and were causing three recurring problems: Frequent mechanical seal failures — water ingress damaged motors and forced repeated emergency repairs, each requiring tank drainage and a shutdown of the treatment line. Sludge sedimentation — insufficient axial thrust allowed solids to settle in corners of the aeration basins, reducing effective tank volume and increasing aeration energy demand. Long spare-part lead times — replacement motors and seals took 8 to 12 weeks to arrive, leaving the plant running on reduced mixing capacity. The contractor needed a replacement supplier able to deliver a large quantity in one batch, provide complete documentation for local regulatory acceptance, and support cold-climate operation without redesigning the existing guide rail system. Selection Process The project team compared four suppliers from Europe and Asia against five criteria: hydraulic performance at the required tank volume, seal reliability, cold-climate suitability, delivery lead time and total cost of ownership. Our QJB series was selected after a technical review of the impeller curve, motor insulation class and seal construction. Mixing duty points were calculated for each tank type and matched to five power ratings. Wetted materials were specified per basin: SS304 for aggressive sludge lines, epoxy-coated cast iron for standard aeration basins. Guide rail brackets were adapted to the client's existing lifting system, avoiding civil works. Documentation package (test reports, material certificates, wiring diagrams, Russian manual) was agreed before production started. Solution: Equipment Configuration ModelPowerImpeller SpeedWetted MaterialQty (pcs) QJB2.2/8-400/3-7402.2 kW740 rpmCast iron, epoxy coated60 QJB3/8-620/3-4803 kW480 rpmCast iron, epoxy coated50 QJB5.5/12-620/3-480S5.5 kW480 rpmSS304 stainless steel45 QJB7.5/12-960/3-4807.5 kW480 rpmCast iron, epoxy coated30 QJB10/12-620/3-48010 kW480 rpmSS304 stainless steel15 Total200 Quality Assurance Before Shipment Every unit passed four inspection stages, and inspection records were issued with the shipment: Motor winding resistance and insulation resistance test Dynamic balancing of impeller and shaft assembly 24-hour continuous running test with current and temperature logging Double mechanical seal pressure and leak test Packaging used fumigation-free plywood cases with foam-secured motor housings, suitable for multimodal rail transport and long inland delivery. Results After Commissioning IndicatorBeforeAfter Mixer-related downtimeRecurring seal failures, 3–4 shutdowns per yearZero unplanned mixer downtime in the first operating period Sludge sedimentationVisible solids build-up in basin cornersUniform solids distribution, full tank volume in use Spare-part lead time8–12 weeksStandard seals and motors shipped from stock Maintenance accessTank drainage requiredGuide rail lifting, inspection without drainage The plant reported stable mixing performance through the cold season, and the contractor has since requested technical selection support for a second phase covering additional anoxic tanks. Why the Client Chose Zhongyi Batch capacity of 200 units with a single delivery schedule and consistent documentation Adaptation to the client's existing guide rail and lifting system Russian-language manuals and CE documentation prepared before shipment Direct technical support during tank-by-tank selection Quzhou Zhongyi Chemicals Co., Ltd. was founded in 2007 and manufactures submersible mixers, sewage pumps and progressive cavity pumps for municipal and industrial wastewater applications, with more than 80% of output exported. Contact our export team to discuss mixer selection for your next treatment plant project.

Quzhou flood control level II emergency response   According to the statistics of the meteorological department, the average rainfall in Quzhou City was 115.7mm from 5:00 on the 19th to 5:00 on the 20th. It is expected that there will be heavy rain in the middle and north of Quzhou City during the day of the 21st, with local heavy rain, and moderate to heavy rain in the South. According to the Quzhou emergency plan for flood and drought control and the Quzhou emergency plan for sudden geological disasters, the municipal flood control index decided to upgrade the flood control level III emergency response to level II from 7:30 on June 20, while maintaining the level IV emergency response for sudden geological disasters. In order to implement specific defense preparations and enhance Quzhou's urban waterlogging emergency response capacity, Quzhou Kecheng District Emergency Management Bureau and Hangbu Industrial Park sent an emergency support letter to our company. In order to alleviate the impact of Waterlogging on people's safe travel, our company sent a 600m ³/ H large flow emergency drainage pump truck is put into operation to support drainage and rescue work.     During the flood control and rescue, our company actively cooperated with the government, vigorously carried forward the spirit of "one party in trouble, eight parties in support", assumed the corporate social responsibility, made rapid response and disposal, ensured the daily safe travel of citizens, protected the people's property, and achieved a phased victory in the flood control and rescue work   The drainage pump plays a great role.