Bangu wastewater treatment plant (Brazil)
The Nereda® technology allows cost-efficient, sustainable and space-saving wastewater treatment, thus, reconciling the most important challenges currently facing the industry. In combination with highly efficient rotary lobe compressors made by AERZEN, significant process, cost and environmental benefits can be achieved. A visit to the wastewater treatment plant in Bangu (Brazil) shows what is possible.
About 245,000 people have their home here in Bangu, a district in the west of Rio de Janeiro, and since May 2022, they have been connected to a central wastewater treatment plant. 43 million litres of wastewater are purified there - all thanks to Nereda® technology and rotary lobe compressors from AERZEN particularly efficient, resource-saving, space-saving and economical.
Nereda® offers economical and ecological advantages
Nereda® is an innovative, patented process for biological wastewater treatment, which was developed in the Netherlands at the Delft University of Technology in cooperation with the Royal HaskoningDHV Engineering Office (RHK). It is based on the Sequencing Batch Reactor (SBR) process and enables maximum capacity increase in the smallest space. The highlight is a special aerobic granular biomass. The large surface area of the granulate allows for a significantly higher population of wastewater-purifying microorganisms and thus a much faster and better purification. All processes run simultaneously; the faster settling speed of the activated sludge also contributes to the shortening of the cycle time. The Nereda® technology combines cost efficiency with sustainability and compactness, giving it a clear advantage compared with conventional biological cleaning processes.
Nereda® plants require significantly less space (25% smaller footprint), achieve energy savings of up to 50%, can dispense with additional chemicals and ensure stable, low-maintenance operation with excellent discharge values.
Bangu: large wastewater treatment plant with small footprint
These process and cost advantages of the Nereda® technology have also convinced the concessionaire Zona Oeste Mais Saneamento. The private concession founded by BRK Ambiental (responsible for the construction of the Bangu wastewater treatment plant) and Águas Do Brasil (responsible for the expansion of wastewater disposal in planning area No. 5 in Rio de Janeiro). The wastewater treatment plant in Bangu is designed for 144,000 population equivalents (p.e.) and has an operating area of 38,000 m². The contaminant load is supplied with a biological oxygen demand (BOD) of 150 mg/l, nitrogen bound (TN) of 35 mg/l and a total suspended solid (TSS) of 170 mg/l and achieves discharge values of <20 mg/l BOD, <5 mg/l NH4 and <10 mg/l TSS - an outstanding cleaning performance. The pre-cleaning system consists of four parallel lines (four mm fine rake, sand trap, grease and oil extractor) with a capacity of 11,000,000 l/d each. The settled sand is transported into containers via a horizontal and a vertical snail and is then disposed of. Due to the extraordinarily compact design, approximately 30% of the footprint can be saved compared to a solution with conventional primary clarifiers. The biological purification stage also manages with very little space. The two Nereda®-SBR basins each have a volume of 6,300 m³ and a depth of 6.15 m and require a total installation area of 13,800 m². A conventional
aeration tank with the same capacity of contaminant load is about 18,500 m² and is thus about 35% larger, which in turn leads to significantly higher investment costs.
Highly efficient rotary lobe compressors made by AERZEN
The compressed air for the biology in Bangu is provided by five AERZEN rotary lobe compressors, type Delta Hybrid D 152S with a drive power of 200 kW each (volume flow between 2,600 and 6,286 Nm³/h, differential pressure = 700 mbar): two packages each for one SBR reactor, one machine serves as redundancy. Rotary lobe compressors - or also called screw blowers - are among the most innovative solutions in compressor technology. They combine the advantages of blower and compressor technology in one system and are by far one of the most efficient packages for a wide control range of 25% to 100%. For the three phases of the Nereda® process - aeration, sedimentation, feeding - the optimum oxygen supply can thus be guaranteed at all times.
Whether aeration tank or sludge treatment: efficiency is the most essential thing
The AERZEN compressors are free of oil and free of absorption material. This guarantees 100% reliability. Silencers without absorption material successfully prevent contamination of the process air or the downstream process system. This is a crucial factor for sustainable, safe and long-lasting operation.
The compact design of the Delta Hybrid D 152S also enables a space-saving side-by-side installation, resulting in a smaller machine room and thus less investment in the building. The wide control range of the rotary lobe compressors is also of decisive importance. As a result, the footprint of the machine room is 20% smaller compared to other blower technologies - even though the D 152S is the largest rotary lobe compressor AERZEN has in its portfolio. Delta Hybrid rotary lobe compressors from AERZEN are even used in sludge treatment, however, in a smaller version. The sludge is dewatered with the help of three centrifugal presses; two D 24S with a volume flow of between 560 and 1,400 m³/h and a differential pressure of 500 mbar assist in the deammonification. The energy-efficient AERZEN packages were chosen because of their relatively long running time of five to six hours a day.
Energy savings of 15 percent
AERZEN packages stand for maximum performance, reliability and economy and are a guarantee for maximum energy efficiency and minimum life-cycle costs - issues which are becoming increasingly important. “When choosing blower technology, many only look at the initial costs. This is fatal, because the purchase price accounts for only five percent of the total operating costs. The costs for energy, service and maintenance are much more important. Energy consumption in particular has an enormous impact of 90%,” says Rainer von Siegert, Managing Director at Aerzen do Brasil, and emphasises: “Anyone who wants to keep life-cycle costs as low as possible should therefore also consider the follow-up costs. Energy-saving and service-friendly packages are the most important thing here.” Lower costs despite higher CapEx? The fact that this calculation works out is made clear by the example of Bangu. Compared to international competitors, the AERZEN compressors were 15% more expensive in the CapEx area, but thanks to the excellent OpEx balance - 7% lower energy costs and significantly lower service and maintenance costs - the 15% additional costs are already amortised after five years. Compared to a competitor solution the five AERZEN rotary lobe compressors D 152S save around 60.000 kWh per year. Mechanical Engineer Jose Pedroso of Zona Oeste Mais Saneamento is correspondingly satisfied: “We are happy to have AERZEN as partner on our side. We expect energy savings of 15% over the next 30 years and look forward to an excellent repair and maintenance service.”
Nereda® Preferred Supplier AERZEN
As the world‘s only official Nereda® supplier for aeration technology (Preferred Supplier since September 2019), AERZEN supports the global wastewater industry with process-safe and forward-looking solutions. “AERZEN is the blower manufacturer of choice for most of our customers and offers a wide range of high quality solutions, meeting the requirements of almost all Nereda® projects. In addition, with AERtronic and AERprogress , there are innovative strategies for optimising the efficiency and availability of the packages. This is important for every aerated system and is in line with one of the main focuses of Nereda® technology, energy efficiency,” Annie Blissit, Manager of the Nereda® Preferred Suppliers Programme, points out and adds: “Furthermore, AERZEN is an exceptionally cooperative partner. Not only do they actively think about new solutions and improvements to the overall offering with our team, but they are also very responsive and always ready to assist our customers with any aeration issues.”
Further Information
More about water and wastewater treatment applications:
https://www.aerzen.com/applications/water-and-waste-water-treatment.html
More about AERZEN rotary lobe compressor Delta Hybrid:
https://www.aerzen.com/product/screw-blowers-delta-hybrid.html
More about Royal HaskoningDHV:
www.royalhaskoningdhv.com
More about BRK Ambiental:
www.brkambiental.com.br
More about the Nereda® conzept:
https://nereda.royalhaskoningdhv.com
