MABR Addresses Unique Treatment Challenges of Municipalities

 

Costs are Rising

Municipal wastewater treatment is becoming more and more expensive due to population growth, increased discharge standards and rising energy costs. Aeration comprises 60% of energy costs in a typical activated sludge treatment process, in addition to this, there is a large capital cost for land and equipment required in the treatment of wastewater.  OxyMem MABR is delivered in a modular design and can be scaled to service any municipal requirement.

When a wastewater treatment plant (WWTP) with a size of 10 000 PE (people equivalent) and flow capacity of 1500m3/day is taken as an example, OxyMem MABR delivers supreme water quality by taking up only 104m2 in comparison to 375m2 footprint required to have a conventional activated sludge (AS) plant operating with a similar treatment capacity.

Footprint comparison of a new built MABR versus AS wastewater treatment plant with PE of 10 000.

Table 1: Footprint comparison of a new built MABR versus AS wastewater treatment plant with PE of 10 000.

 

Employing OxyMem’s MABR takes over 3.6 times smaller footprint.

It is possible, as OxyMem MABR module with 500m3 working volume successfully replaces 1500m3 of AS installation. As depicted in the process flow diagram below (Figure 1a), the anoxic and aerobic combined phase tank is accompanied with a settler unit. OxyMem MABR due to:

  • membrane increased surface area,

  • bubble-less technology of aeration,

  • high oxygen transfer rates directly to biofilm,

  • aerobic and anoxic zones comprised within the biofilm itself,

  • more efficient mixing provided by air-lift technology,

  • and biofilm growth on membranes acting also like a biofilter,

 

packs all these elements in one easy to set up and operate installation (Figure 1b).

What’s more, OxyMem MABR can significantly improve discharged water quality, if placed after the conventional municipal wastewater treatment system, taking up minimum space. It can act as a secondary treatment, for example supporting lagoon type WWTP.

Please view our SABESP case study.

 

 

Figure 1a: Configuration of a conventional activated sludge municipal WWTP

Figure 1a: Configuration of a conventional activated sludge municipal WWTP

 

Figure 1b: Configuration of a MABR municipal WWTP

Figure 1b: Configuration of an MABR municipal WWTP

 


Energy costs significantly reduced

When looking closer at the operational costs of the municipal 10 000 PE WWTP, OxyMem MABR requires only a fifth of the energy used by the conventional AS installation. This brings, taken into account price of the energy set at 0.1€/kWh, savings of 14 000 € per year.

Table 2

Table 2: Energy consumption comparison for a new built MABR versus AS wastewater treatment plant with PE of 10 000.

 

There are few general reasons for this significant energy savings:

 

  • OxyMem MABR in comparison to AS system requires less aeration energy. The system does not rely on the pressure difference to transfer the oxygen and the pressure drop over the length of the module is so low that it is possible to operate blowers with low discharge pressure (150 – 200 mbar).

  • OxyMem MABR includes innovative reverse airlift technology to provide a maximum wastewater stream mixing within the module, so there is no need for energy expenditure for mixing as it is necessary for the anoxic tank of the AS WWTP.

  • In OxyMem MABR module fixed biofilm growth on the membranes limits the unwanted excess sludge production. Consequently, the sludge return is redundant, and there is no energy spent to run pumps for returning it, like in AS WWTP where it is transferred from the settler back to the bioreactor.

 

The indicative energy usage data of OxyMem MABR are available in Severn Trent case study.

 


Capacity Needs are Incremental

Table 3

Table 3: Footprint and energy consumption comparison for a 50% additional capacity retrofit MABR to a conventional AS PE 10 000 WWTP.

Drop-in expansion of biological plant capacity (IFAS style deployment for overloaded or underperforming plants). MABR can be delivered without draining the tanks or interfering with the existing process.

Sweating the Assets

Deliver 50% additional treatment capacity in a matter of weeks without draining the tanks adding 50% more capacity to the WWTP by retrofitting a conventional AS system is costly, time-consuming and requires 187.5 m2 available space to be built on (Table). OxyMem MABR module gives a unique possibility to instantly increase the capacity of the existing AS WWTP without creating any additional footprint.

Operational advantages of adding OxyMem MABR as a retrofit.

Increasing the capacity of the existing WWTP by 50% corresponds to 50% rise in the energy costs increase when upgrading with AS system. In the case of retrofitting with OxyMem MABR, operational energy expenditure for a year is 1 901 € versus 8 950 € spent additionally for the new AS system. This brings an AS WWTP with MABR retrofit by having advantages of:

 

  • 50% more wastewater treatment capacity,

  • no additional footprint,

  • and 7 049 € savings a year.

 

Figure 2

Figure 2: Configuration of a conventional activated sludge municipal WWTP with a Drop-in retrofit MABR.

 


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