Sewer monitoring
H₂S monitoring & dosing performance optimisation
Who this is for
Wastewater operations managers and sewer process engineers
Your operating priority
Distinguish real H₂S treatment performance from changes in flow, weather or sensor conditions, without tying the review to a chemical supplier.
Before you specify or buy
Agree baseline and trial windows, monitoring locations, calibration checks and dose records before interpreting a treatment comparison. The existing chemistry may be supplied by Critical Elixirs or another provider.
Critical Elixirs field work
H₂S assessment starts with work at the access point
Gas measurements, water-quality checks, sampling and equipment inspection support a monitoring programme. The methyl mercaptan instrument shown measures a different compound from H₂S; spot readings are not a controlled treatment comparison.
Methyl mercaptan field measurement. A spot reading is not a worker-exposure assessment or a treatment comparison. 
pH and oxidation-reduction potential (ORP) measurements help interpret water conditions alongside sampling and calibration records. 
Site sampling and water-quality measurement. Sample location, handling and instrument checks affect interpretation. 
A field dosing installation. Equipment configuration and operating settings are confirmed against the duty. 
Field pH, ORP and dissolved-oxygen measurements. ORP is not a direct SRB count or proof of sulphide removal. 
Field pH measurement. Calibration, sample conditions and treatment objectives are needed to interpret the reading.
What is covered
- Review peaks and percentiles alongside ORP, pH, oxygen and residual data where available.
- Include complaints or operational observations where relevant to the assessment.
- Relate monitoring locations and times to network conditions and actual dose delivery; the chemical supplier does not determine whether the service can be scoped.
- Agree baseline, monitoring period and reporting basis before interpreting changes.
What we will ask you
- Monitoring records and sensor locations
- Dose points, settings and network operating conditions
- Relevant complaints, maintenance events and intended measures
This page is information only. Pricing, availability and specifications are provided through an enquiry.
Straight answers
Frequently asked questions
- How do operators know whether H2S chemical dosing is working?
- Agree baseline and trial measurements at relevant locations, verify delivered dose and compare similar network conditions and travel times. Read peak, P95 and exceedance duration together with valid data coverage, sensor checks and an explicitly defined assessment threshold. A single low gas reading does not prove sustained performance, complete sulphide removal or worker exposure compliance.
- Which measurements may be reviewed?
- Depending on the site, the review can consider H₂S peaks and percentiles, ORP, pH, oxygen, residuals and relevant complaint records.
- Can you review performance with chemistry from another supplier?
- Yes. Performance optimisation and reporting can be scoped independently of chemical supply, using agreed monitoring, network and dosing data.
- Does a process gas logger establish worker exposure compliance?
- No. Process monitoring is not personal exposure monitoring and does not establish occupational exposure compliance.
- What do peak, P95 and exceedance duration tell us?
- Peak is the highest valid recorded concentration; P95 is the concentration at or below which approximately 95% of valid observations lie under a stated calculation method. Exceedance duration reports time above a specified threshold. State units, logging and averaging intervals, valid coverage and threshold purpose. Gaps are unknown, not zero; compare like-for-like operating periods and sensor checks.
H₂S, methyl mercaptan, pH, ORP and SRB testing
H₂S and methyl mercaptan are different sulphur compounds; an instrument reading for one must not be presented as a result for the other. pH and oxidation-reduction potential (ORP) provide water-condition context alongside appropriate gas and liquid sampling. Where sulphate-reducing bacteria (SRB) testing is included in the scope, agree the sample method and laboratory interpretation. ORP or a photograph alone does not identify or quantify SRB. Conductivity and total dissolved solids (TDS) information can add water-quality context, but a conductivity-derived TDS estimate is not a direct H₂S or SRB test.
Compare dosing performance using an agreed baseline, monitoring locations, operating conditions and calibrated instruments. The photographs below document field activity, not a before-and-after treatment result or proof of exposure compliance.