Lower energy cost for wastewater treatment plants
Using an advanced process and energy simulator, Delprosa demonstrates how to cut electricity costs while maintaining effluent quality.
Maximising the benefit from the tariff
How much a tariff costs per annum is a complex question that depends on the plant configuration and how it is operated. Historical data doesn’t tell you what can be achieved using advanced price responsive control. Done well, the same treatment costs less.
The simulation model reveals what can be achieved. Processes that can wait are moved to times when energy is cheaper without losing the savings to higher peak demand. Constraints such as effluent quality or equipment limits are never compromised.
The simulation
This worked example shows the simulated result of a 55 ML/day plant with full biological treatment up to 3xADWF. The liquids stream comprises primary settling, 30 ML bioreactor with anaerobic and pre and post anoxic zones, secondary clarifiers, and disinfection before pump out from an 8ML reservoir via 500 L/s effluent pumps. RAS and dewatering return streams are included as well as internal nitrates recycle in the bioreactor. Sludge goes to an anaerobic digester with a 750 Nm3 gas holder with biogas being used through 300 kW cogen engine and boiler for maintaining digester temperature. A 200 kWp solar PV system and 2MWh BESS is included in the analysis and control scheme.
The type of problems we can solve
Will an alternate tariff be cheaper overall?
The plant is run under the current contract and under the alternate offer over the same time period. Energy, demand and fixed charges are reported separately, to evaluate whether there is a cost saving or not. The cheapest contract depends on how the plant’s load falls across the billing periods, so it is rarely the one with the lowest unit rate.
Does solar or a battery pay for itself?
Solar, a battery or cogeneration is added to the plant and dispatched against its own load and the tariff’s demand windows. The result is a capital cost, an annual saving and a payback. The value comes from when the output arrives: the expensive hours pay for it, not the yearly total.
Can load be moved without breaching effluent limits?
Aeration, pumping and sludge handling are shifted in time, and the effect is reported on the energy bill and on effluent quality against your limits in every case. The same loads that swing the bill are the ones holding the effluent within limits, so the room to move is narrow.
What is the best way to debottleneck the plant?
Tanks, pumps, blowers and sludge operations are checked against the loads they actually receive. Where something is undersized the run says so. The in-built sizing guide is a fast way to pinpoint issues quickly. The constraint moves with the flow, so the part that looks small is often the one holding the plant back.
How the savings are found
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01
Set up the plant and tariff
Your plant is built from your own data, and your current and alternative electricity tariffs are loaded with it.
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02
Run the simulation
A full year at five-minute resolution, with local weather driving the flows and temperatures.
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03
Compare the cases
Standard against price-responsive control: cost line by line, quality against your limits, and net present value.
How we are engaged
What our fee covers
Delprosa provides a consulting service using the simulation model. We can take full responsibility for configuring the model, analysing the results, preparing the business case, managing the implementation of price-responsive control and monitoring it afterwards. Alternatively, you can self-manage any part of that under a licence to the model, with an agreement that sets what each person can change, so the tool always fits the service you have chosen.
Contract changes
A retail contract is between your organisation and your retailer. Delprosa is not party to it, does not negotiate on your behalf and takes no commission from any retailer. We are paid a fee for the work, agreed before it starts, and that fee is our only income: the whole of the saving stays with you. With this approach, we stay independent of the offers on the table and have no vested interest in inflating the results.