Membrane bioreactors can be an effective alternative to conventional activated sludge, especially where concentrated wastewater must be treated or conditions require high efficiency and compact footprint.

Cannon Artes offers the EmbioArt MBR, with broad applications in the municipal and industrial wastewater treatment sectors. The company says the technology yields high-quality effluent that meets water reuse requirements.

The treatment process combines an aeration basin with membranes. The membrane modules are submerged in a dedicated basin downstream of the biological reactor. The number of trains can be optimized based on customer requirements, and the system is delivered complete with all control and safety devices.

In the MBR basin, the process can operate with mixed liquor suspended solids up to 12,000 mg/L, so that a lower volume is required. The system is designed to be flexible based on customer requirements in layout, air consumption, chemicals and energy. The process is fully automated.

Serena De Maria, Ph.D., research and development engineer and process specialist with Cannon Artes, talked about the technology in an interview with Treatment Plant Operator.

TPO: How would you characterize the basics of this technology?

De Maria: EmbioArt is an improved version of conventional activated sludge reactors. It consists of biological treatment in which the downstream solids-liquid separation is carried out by membranes instead of a secondary clarifier. The absence of settling constraints allows higher mixed liquor suspended solids in the aeration basin and a longer sludge retention time. The result is more efficient treatment that complies with water quality requirements for reuse.

TPO: How do you differentiate EmbioArt from other MBRs?

De Maria: It is a complete turnkey system. We provide a tailor-made solution based on the application, inlet water characteristics, and technical requirements. We supply the core membranes and all supporting components, starting from optimized pretreatment to limit solids accumulation and fouling on the membranes. We design the biological section through careful evaluation of the kinetic and operative parameters and the selection of membranes. Finally, we monitor all the phases of the operative cycle, cleanings and maintenance.

TPO: What are the sweet-spot applications for this MBR?

De Maria: The advantages of reduced footprint and high efficiency can be observed at small and large installations for municipal and industrial wastewater. For municipal facilities, the technology treats high organic loads and can be easily expanded to accommodate growth. In food and beverage processing, the system can handle very high organic loads that could not be treated with conventional activated sludge. In pharmaceuticals it allows pretreatment of micropollutants; in petrochemicals it is advantageous for water reuse. In pulp and paper its use for water reclamation is important due to the large amount of process water needed.

TPO: In basic terms, how does the treatment process work?

De Maria: Wastewater goes through a pretreatment step designed based on site-specific water quality to minimize suspended solids as well as oil that could interfere with the biological process and cause membranes fouling. The influent stream then undergoes biological treatment where biomass concentration is much higher than in conventional treatment. This provides the same results at lower volumes, reducing the plant footprint.

In addition, older sludge (higher sludge retention time) is more efficient and well stabilized, and so the required wasting of sludge is lower. Solid-liquid separation from the biological section is fed to the membranes, which are provided in different configurations (hollow fiber or flat sheets) and different materials. During filtration, treated water is extracted from the membrane basin to a dedicated treated water basin. The filtration phase is alternated with backwashing, relaxation and ventilation as well as cleaning and air scouring, which are optimized and monitored based on specific water characteristics to minimize energy consumption and chemical dosages.

TPO: What effluent pollutant levels can the unit achieve?

De Maria: Long solids retention time enables effective nutrient reduction and effluent BOD of less than 1 mg/L. Nitrogen and phosphorus can be further reduced by optimized alternation of aerated and anoxic zones. Membrane modules downstream from the biological section deliver less than 5 mg/L TSS less than 30 mg/L COD. In addition, membrane pores in the ultrafiltration range enable separation of viruses and bacteria, possibly meeting disinfection requirements and avoiding tertiary treatment.

TPO: What makes the technology’s small footprint possible?

De Maria: The required tank volumes are lower than for conventional activated sludge reactors, and the system operates at the same MLSS in lower volumes. The footprint is also smaller because clarifiers are replaced with a more compact membrane unit. A compact footprint is particularly advantageous when space is limited and when treatment facilities must be expanded in constricted spaces.

TPO: How much operator attention is required to run the unit?

De Maria: Aside from a startup phase and recovery cleaning, which should be performed a few times a year to restore membrane permeability, all operations can be considered automatic. This is an advantage in view of the many and frequent steps that make up the technology, both during regular operation (filtration, relaxation, ventilation, backwashing) and maintenance cleaning with sodium hypochlorite and acid. To meet site-specific treatment requirements, sophisticated software allows presetting of all parameters, such as dosages and frequencies and the duration of each step, and enables remote monitoring. This helps save on energy and chemicals.

TPO: How does this unit compare with others in energy efficiency?

De Maria: Energy is consumed by the air scouring necessary to counteract membrane fouling. When high performance is required, conventional biological treatment would require additional and more energy-intensive and costly treatment. In addition, careful monitoring of maintenance cleanings by integrated software helps avoid start/stops and overdosages, reducing energy costs.