Engineering Tool · Chemistry

Chlorine / Chloramine CT & Residual Designer

Calculate theoretical and baffled contact time, measured residual CT, and separate segment-based exposure summaries.

Municipal Drinking WaterStage 05 — Disinfection

Status: Available

PROJECT · OPTIONAL

Project metadata

Optional report context; it does not change calculations.Edit detailsHide details

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01 · USER INPUT

Design basis and inputs

Initial residual basisInitial residual basisSelect the active source of the initial residual

Disinfectant dosemg/L as Cl2User-entered disinfectant demandmg/L as Cl2

Measured final outlet residualOptional · blank means not enteredEntered zero is a measured result and is used for the final Residual × T10 term.User-entered CT criterionOptional · blank means not enteredBlank means no criterion comparison. Zero is inactive.

Contact configurationContact configurationChoose one hydraulic basis

Design flowm³/dContact basin volumem³Baffling factorfractionRequired range: 0 to 1.First-order decay constantmin⁻¹

Browser calculation. Criterion comparisons are screening only; no regulatory compliance conclusion or pathogen credit is provided.

02 · CALCULATED RESULT

Structured results

Enter the active design basis, then calculate to create a result.

03 · REPORTING

Exports and verification

Exports include only the selected residual basis and active contact configuration. A current result is required.

Verification suite

Calculation revision 1.1

Focused deterministic tests cover single-basin and multi-segment residual propagation, CT methods, optional criteria, active basis selection, and validation.

Engineering Basis

Methodology

Uses the selected dose-minus-demand or measured-residual branch and nominal detention with an entered baffling factor to screen segment residual and CT. User-entered criteria and generic decay assumptions are not automatic regulatory CT credit or a regulatory CT calculation.

Available calculation branches are dose-minus-demand or directly measured initial residual, and single-basin or serial multi-segment contact. There is no separate free-chlorine/chloramine selector; the same generic user-entered decay model is used for either intended chemistry.

Calculated initial residual = max(dose − user-entered demand, 0), unless directly measured initial residual is selected.

First-order modeled residual uses Cend = Cstart exp(−kT10) in each contact segment.

Theoretical detention = volume / flow. T10 = user-entered baffling factor × theoretical detention.

Multi-segment Residual × T10 sums each segment modeled end residual × segment T10, using an entered measured final outlet residual for the final segment term when supplied, including 0 mg/L.

Integrated first-order exposure sums Cstart(1−exp(−kT10))/k, with the k=0 limit Cstart×T10.

The user-entered CT criterion compares with single-basin Residual × T10 or, in multi-segment mode, segment-summed Residual × T10. This is not regulatory CT credit.

Scope / Limitations

Keep residual×T10 segment sums distinct from outlet residual×total T10 and integrated first-order exposure; a measured zero residual is valid.
Residuals, dose, and demand use an entered chlorine-equivalent basis in mg/L as Cl2. The model does not distinguish free chlorine from chloramine, model chemical-specific reactions, or select chemistry-specific decay coefficients.
There are no pH, temperature, organism, log-inactivation, or reference CT-table inputs. This tool does not calculate required CT or regulatory/pathogen credit; the user-entered CT criterion is a comparison value only.
No jurisdiction-specific compliance conclusion, automatic pathogen credit, DBP prediction, or chemical recommendation.
Regulatory CT profiling uses measured residual and peak-hour flow for each disinfection segment. This screen uses a user-entered design flow in m³/d, baffling-factor estimates, model-derived intermediate residuals, and at most one measured final residual; its Residual × T10 outputs are not regulatory CTcalc.
Baffling factor and decay constant are project inputs. Integrated first-order exposure is not automatically equivalent to a regulatory CT-credit method.

Engineering Path

Upstream Context

Targeted advanced-treatment basis Only carry forward an adsorption or oxidation barrier when a named water-quality objective supports it.

Current Tool Decision

Chlorine / Chloramine CT & Residual Designer Calculate theoretical and baffled contact time, measured residual CT, and separate segment-based exposure summaries.

Downstream Engineering Step

Clearwell & Storage Turnover Designer Coordinate the selected disinfection approach with storage and finished-water checks; a screening result is not regulatory credit.