How to save energy consumption in a WWTP and enhance nutrient removal through online aeration control,

the case of OptimEDAR

INTRODUCTIONAt present, about 71,000 municipal WWTPs are operational in the 28 EU member states, Iceland, Norway and Switzerland [1]. In conventional activated sludge WWTP, nearly 50% of the energy is used by the in the biological reactors [2]. Therefore, any % of decrease of energy consumption in this process means a significant reduction in the energy bill for the whole plant.

Furthermore, EU Directive 91/271/EEC (UWWTD), under article 5, specifies that more stringent treatment must be applied in areas identified as sensitive by the member states, in particular improving the reduction of total nitrogen and phosphorus load. That means that new investments for additional treatments are expected, in particular in some EU countries where the level of compliance with article 5 is still low [3].

Finally, EC is concerned about the slow progress in improving the status of the European water bodies [4]. As the amount of treated wastewater increases, in application of the UWWTD, the WWTPs are becoming one of the most important sources of polluting discharges. Despite the huge investment efforts in building the sewage and treatment facilities, now it is time for increasing the WWTPs efficiency and environmental performance.

Montserrat BATLLE [mbatlle@adasasistemas.com - T: +34 93 264 06 02]

Pedro MARTIN DE LA VEGA [pedromm@unex.es]

Ernest MEJÍAS [ernest.mejias@teqma.com]

METHODSDescription

Innovative online monitoring and control of the aeration process in biological reactors.

- Measuring Dissolved Oxygen (DO) and Oxidation-Reduction Potential (ORP), their temporal evolution and trend, the probabilistic and logic mathematical algorithms calculate the Equivalent Organic Charge (EOC), an estimation of the organic matter load in the bioreactor.

- When organic load is low, longer non-blowing cycles can be allowed, bringing the reactor into denitrification conditions, as well as saving energy.

- The controller manages microorganism oxygen demands for organic material removal, ensuring that organic matter is available for Phosphorous Accumulating Organisms (PAOs) during non-aeration cycles. This management allows enhanced biological phosphorus removal.

- OptimEDAR provides the optimal environment for the bacteria, thanks to the organic matter management and the microbiological stability achieved.

- OptimEDAR is an ‘add-in‘ solution, easy to install, based on robust probes with low maintenance requirements.

DISCUSSIONThe OptimEDAR innovative approach relies on the deep knowledge of the dynamics of the biological process and the application of ‘virtual sensing’ techniques based on the data from low-cost and robust probes.

OptimEDAR characteristics compared with other existing control methods:• Time On-Off: Is blowing without knowing the organic matter load and assuming that

denitrification process is correctly performed during the anoxic stage.• Oxygen set point: The energy consumption of the blowers is not optimised and assumes

that denitrification process is correctly performed during the anoxic stage.• Ph control: Similar to OptimEDAR, but the whole operation depends on a small precision

range of the pH probe, requiring additional calibration efforts.• Ammonia control: Requires a costly analyser with high maintenance requirements

In Figure 2 it is observed how OptimEDAR prioritizes the use of organic matter in order to improve nutrient removal processes, avoiding over-aerate the system and reducing the numberof alternating cycles. As a result, the management of organic matter is optimal.

Figure 1. OptimEDAR Solution

Figure 2. Evolution of oxygen and RedOx in Empuriabrava aeration tank before (top) and after (bottom) OptimEDAR controlling.

Applicability

OptimEDAR might introduce better ratios of improvement in:• Extended aeration WWTPs with Oxidation Ditch Configuration.• WWTPs where the influent suffers significant load and flow cyclic variations over a 24-hour

period, weekend or seasonal peaks.• Most EU WWTP with biological nutrient removal where designed with USEPA method, therefore

normally oversized.

Table 1. OptimEDAR vs other Technologies.

inspiring change www.iwahq.org

References: [1] New study on European municipal wastewater treatment plants. (http://www.recyclingportal.eu/artikel/31656.shtml) [2] Energy Resources Center. (http://www.erc.uic.edu/energy-efficiency/illinois-energy-now-programs/waste-water-treatment-facilities-program/) [3] http://www.eea.europa.eu/data-and-maps/uwwtd/interactive-maps/urban-waste-water-treatment-maps-1 [4] http://ec.europa.eu/environment/news/efe/articles/2015/04/article_20150410_01_en.htm

RESULTSWithin the R3Water project, the OptimEDAR is being demonstrated in Wijer (Aquafin, Belgium) (1,440 P.E., design flow max. 2470 m3/day) and in Empuriabrava (CCB, Spain) (70,000 P.E., 16,000 m3/day), as cases of study for a small plant in different climatic conditions and a big plant with highly seasonality.

Empuriabrava (SPAIN)Some preliminary results achieved in Empuriabrava during the first 4 months of 2016 showed a decrease of 24.4% in the blower’s operation.

Figure 3. Energy consumption before and after OptimEDAR controlling.

24.4%

Although the performance baseline for nutrients and organic matter removal was really high, some slight improvements have been observed regarding performance:• BOD removal from 97.8% to 98.5%.• COD reduction from 90.6% to 93.5%.• Total Nitrogen removal, from 87.1% to 91.3%.

CONCLUSIONS•Reduce energy consumption, by average 20%, by adapting blower operation to

the current organic matter load.

• Increasetheefficiencyofthenutrientsremovalduetodenitrification-dephosphatationcycles and provides microbiological stability.

•Minimise CO2 emissions.

•Low investment and low maintenance requirements.

AcknowledgementThe authors would like to thank you for the support of R3Water, CCB (Consorci Costa Brava), Aigües de la Costa Brava (EMACBSA) and Aquafin.

Energy Cost

www.adasaproducts.com

1

Dissolved Oxygen SensorRedOx Sensor

3 Control Cabinet

2 Sensor Cabinet

4 Control Centre