Energy, Materials and Economic Comparison

Define consumption and the comparison boundary

A resource balance turns a treatment proposal into an assessable operation. Its first decision is not the electricity price but the boundary: which equipment, schedules, volumes and residues are included. Module consumption is not necessarily treatment-train consumption; train consumption does not always equal the increment attributable to adding it to an existing facility. Mixing these boundaries can produce apparent savings even when every individual reading is correct.

For the proprietary commercial Aguas SB T1 method, preliminary calculations use the declared T1 2.3 values. These values support a reproducible estimate but do not replace campaign submetering. Comparisons must retain the same useful treated volume and comparable final quality. Lower expenditure achieved by missing the treatment objective does not constitute an energy improvement in the service delivered.

From power to specific energy

At constant power, E=P*t, with P in kW, t in h and E in kWh. When power varies, E=integral(P(t) dt); an integrating meter avoids replacing a variable load with a single reading. For several consumers, energies over equivalent intervals are added and divided by the net volume actually treated, not by the volume passing repeatedly through the pump.

For identical modules, with flow q and exposure c=n*q*t/V, the result is E/V=n*P*t/V=(P/q)*c. Cancelling n and t is algebraic, not a claim that every arrangement has identical performance or actual power. It requires q and P to correspond to the operating condition and no additional consumption to be omitted. In hydraulic series, c may count contacts with units; that definition must be preserved when interpreting the result.

The final column corresponds to one unit of c. It is not a universal efficiency ranking: equipment must also be compared through achievable exposure, obtained quality, capacity and auxiliaries. A larger machine may have a lower nominal ratio yet be unsuitable for the required schedule or flow.

Example 1: Estimate and meter reading

At four cycles, the declared calculation gives 0.5133, 0.3233 and 0.2567 kWh/m3, respectively. These are arithmetic model outputs, not new measurements of efficacy or actual consumption. In a synthetic 10 m3 scenario using T1-16 at c=4, equivalent operating time is t=4*10/15=2.6667 h; estimated energy is 1.925*2.6667=5.1333 kWh.

Suppose, solely to illustrate the boundary, an independent auxiliary consumes 0.25 kW over that interval. It would add 0.6667 kWh, giving a synthetic total of 5.8 kWh, or 0.58 kWh/m3. Before adding it in a real project, its exclusion from the declared power must be confirmed. Double-counting and omission are symmetrical errors.

The verification mini-protocol records initial and final meter readings, net volume, starts, stops and the state of each auxiliary. A second column retains the nominal estimate. The difference is not silently corrected: investigation asks whether it reflects schedule, load, flow, electrical efficiency or boundary. In a direct-current circuit, the corresponding voltage and current are measured; that current must not be multiplied by the alternating-current supply voltage.

What energy per kilogram removed means

With concentration in mg/L and volume in m3, equivalent mass removed from a closed aqueous phase is delta_m=V*(Cin-Cout)/1000, in kg. Mass-specific energy is SEC=E/delta_m. Where inflows, purges or volume changes exist, a load balance replaces that concentration difference. The denominator must be named: kg of COD equivalent removed from water, kg of nitrogen removed and kg of separated solids are not interchangeable.

When the concentration difference approaches analytical uncertainty, SEC can become unstable. A small denominator change produces a large ratio change. In that domain, energy per volume and load difference with uncertainty should be reported, without presenting an impressive ratio as an equipment property. Negative removal must not be converted to zero before the balance is examined either.

Gross savings, net savings and train order

Gross energy savings are consumption avoided in a reference operation. Net savings subtract added consumption: Snet=Eavoided-Eadditional. Both quantities must preserve their sign and share a time horizon. Positive gross savings can coexist with negative net savings. Avoided energy also does not automatically equal bill savings, which depend on fixed charges, contracted power, time-dependent prices and other contractual items.

If T1 precedes biological treatment, reducing susceptible load may change aeration demand, but savings depend on actual blower and control responses. Mixing minima, oxygen maintenance, nitrification and load variation constrain a proportional conversion between COD removed and kWh avoided. Carbon removal can also change its availability for subsequent biological operations. The train and its objectives must be measured, not simply a COD decrease.

If T1 follows biological treatment, it may serve as a polishing operation and must not be retrospectively credited with upstream aeration savings. The core uses combo for conventional treatment followed by T1, whereas energy calculations may examine T1 before biology. These are different scenarios. The process diagram is part of the economic result and must accompany any comparative figure.

Example 2: Preserve negative savings

In a synthetic daily exercise, a reference operation consumes 120 kWh/day. Following an intervention maintaining the same service, that operation would consume 95 kWh/day, while the added treatment and its auxiliaries would consume 32 kWh/day. Gross savings would be 25 kWh/day; net savings would be -7 kWh/day. The complete system would move from 120 to 127 kWh/day. None of these figures describes a real installation.

The conclusion is not that the intervention has no value: it might pursue different quality or capacity objectives. The energy conclusion is that it consumes more under these assumptions. A savings claim would require another verified scenario. A before-and-after trial should record flow, loads, temperature, final quality and control rules; without that comparability, consumption changes may reflect service changes rather than the added treatment.

Materials and maintenance as balances

Chapter 04 develops Faraday's law and its assumptions; the concern here is connecting that physical check to materials accounting without repeating the derivation. The theoretical electrode mass is neither an invoice nor necessarily the mass recovered in sludge. Electrodes should be weighed using a reproducible procedure, cleaning recorded, and lost material distinguished from dissolved metal and metal retained in solids.

Passivation and parallel reactions justify supplementing current and time with material observations. Experimental electrocoagulation studies show that actual wear and passivation response depend on tested conditions, so a universal efficiency correction is inappropriate. Electrode dissolution, passivation and composition.

Example 3: Practical consumables accounting

The third mini-protocol weighs initial inventory, identifies replenishment and accounts for final inventory over a defined campaign. It records commercial reagent and active fraction separately, along with dilution water, wet sludge and dry matter. Specific consumption is divided by net treated volume. A moisture change must not be interpreted as additional dry-solids production, nor a charge per cubic metre as a measured metal dose.

Maintenance hours, cleaning, downtime and replaced parts should also be included. This distinguishes variable consumption from exceptional replacement. The record allows investigation of whether longer operation reduces available capacity or changes unit cost, even when electrical expenditure per volume remains similar.

Model cost and commercial decisions

T1 2.3 incorporates economic assumptions including electrode cost of 0.12 EUR/m3, activated chemistry at 0.22 EUR/m3, annual parts at 6% of CAPEX and eight-year depreciation. These are calculation inputs, not measured consumption or a binding quotation. Their use requires checking coverage and avoiding duplicate accounting. Taxes, financing, waste management and contractual conditions need their own boundaries.

The metric savingM3=max(0,reference-total) clips additional costs to zero. It must therefore be accompanied by the signed difference reference-total: zero in the first metric does not demonstrate break-even. A defensible decision compares alternatives delivering the same service, declares omitted items and preserves adverse scenarios. Reproducing a cost through the public bank demonstrates arithmetic traceability; verifying consumption and a quotation requires distinct operational and commercial evidence.