Demand-Response Application in Wastewater Treatment Plants Using Compressed Air Storage System: A Modelling Approach

Abstract

Wastewater treatment plants (WWTPs) are known to be one of the most energy-intensive industrial sectors. In this work, demand response was applied to the biological phase of wastewater treatment to reduce plant electricity cost, considering that the daily peak in flowrate typically coincides with the maximum electricity price. Compressed air storage system, composed of a compressor and an air storage tank, was proposed to allow energy cost reduction. A multi-objective modelling approach was applied by analyzing different scenarios (with and without anaerobic digestion, AD), considering both plant characteristics (in terms of treated flowrate and influent chemical oxygen demand, COD, concentration) and storage system properties (volume, air pressure), together with the current Italian market economic conditions. The results highlight that air tank volume has a strong positive influence on the obtainable economic savings, with a less significant impact held by air pressure, COD concentration and flowrate. In addition, biogas exploitation from AD led to an improvement in economic indices. The developed model is highly flexible and can be applied to different WWTPs and market conditions.

Alternative seagrass wrack management practices in the circular bioeconomy framework: A life cycle assessment approach

“…Regarding the digester, the thermal energy request was calculated considering 2 distinct contributions: the energy needed for heating the incoming material to the desired mesophilic temperature (35 °C), and the energy requested to balance the losses throughout reactor walls. These two terms were calculated as proposed by (Cottes et al, 2020), considering the real geometric dimensions of the reactor, while the specific heat coefficients for seagrass and sludge were taken respectively from (Caldana, 2012) and (Cottes et al, 2020). The mean environmental temperature was obtained from Regional databases (Osmer FVG, 2020).…”

“…Operating costs would include electricity, water and labour costs needed in the grinding and washing phases, and the augmented operating costs for both the WWTP and composting facility (due to seagrass wrack inclusion). The water tariff considered was 1,41 €/m 3 (Irisacqua, 2019), while for electricity the average price paid by the WWTP (0,15 €/kWh) was used and the same cost was assumed, in addition, for the composting plant (Cottes et al, 2020). As the grinding phase was supposed to be mechanical, the additional labour cost was associated only with the washing process.…”

“…Biogas m 3 34.62 (Misson et al, 2020) Electricity prod. kWh 62.17 (Cottes et al, 2020;Misson et al, 2020) Heat prod. kWh 71.05 (Cottes et al, 2020;…”

“…Electricity (from grid) kWh 27.60 (Cottes et al, 2020;Misson et al, 2020) NP (Inorganic Fertilizers) (Angelidaki et al, 2017;Barampouti et al -12,195,000 -11,795,452 -400,000 4,50% -13,719,375 -13,319,827 -400,000 5,00% -15,243,750 -14,844,202 -400,000…”

Integrating Pyrolysis or Combustion with Scrubbing to Maximize the Nutrient and Energy Recovery from Municipal Sewage Sludge

“…Furthermore, 50-60% of operating costs are taken by sludge treatment whereas electric energy takes a 25-40% share of total operating costs [4]. Therefore, efficient energy and nutrient recovery from a WWTP can lead to a better efficiency and reduced costs [17].…”