Ongoing quality review and monitoring

ZDHC Approved Wastewater and Sludge Laboratories are subject to continuous performance monitoring throughout the approval period. Monitoring is conducted to ensure technical competence, data reliability, and programme integrity. Evaluation may include review of reporting accuracy, completeness of submissions, quality findings management, proficiency testing performance, and responsiveness to programme enquiries. Findings identified during monitoring should trigger root cause analysis and Corrective Action Plans, targeted reviews, or remote or on-site audits, depending on risk level and quality performance.

Key Areas of Review

The following key areas of review constitute the core audit criteria used to verify a laboratory’s ongoing technical competency. ZDHC Approved Wastewater and Sludge Laboratories must maintain continuous readiness across these domains to demonstrate the data integrity and operational transparency required for the Roadmap to Zero Programme.

• Accuracy and completeness of analytical data and test reports.
• Conformance of uploaded evidence in On-site App Projects.
• Correct reporting within the ZDHC Gateway Wastewater Module, including discharge classification, sample description, and test result interpretation
• Validity of accreditation certificates and scope coverage.
• Appropriateness of analytical methods for wastewater and sludge according to the Wastewater and Sludge Guidelines , including verification of LOQ and method validation status and subcontracting activities.
• Suitability, calibration and maintenance control of testing equipment.
• Technical documentation covering analytical methods, quality assurance testing, sampling and chain-of-custody procedures and laboratory information systems.
• Competency records of key personnel, including training, qualifications and authorisation matrices.
• Proficiency testing participation records and corrective actions for unsatisfactory performance.
• Data integrity controls, including result validation, report authorisation, electronic security, and backup systems.

Proficiency Tests 

Participation in proficiency key wastewater and sludge parameter testing schemes is mandatory for all Approved Wastewater and Sludge Laboratories. Laboratories should receive the Proficiency Test booklet updated periodically according to the programme and scope.

Results should be reviewed upon receipt. Any unsatisfactory performance requires a documented root cause analysis and corrective action.

Repeated failures, including across multiple parameters, or an inability to demonstrate effective corrective action may lead to restricted scope approval, audit initiation, or suspension.

Assessment and document assessment activities

Asssessments may be conducted based on investigation outcomes, performance concerns, proficiency testing failures, or major incidents. ZDHC also reserves the right to initiate and perform audits at any time when deemed necessary to ensure compliance, quality assurance, and programme integrity.

Audits may be performed on-site or remotely and shall assess sample handling, chain-of-custody, analytical execution, quality control practices, calibration systems, data integrity, report authorisation, and corrective action effectiveness.

Audit findings are classified according to severity. Major non-conformities require timely closure and verification prior to continuation of critical services.

Audit reports and corrective action records must be retained.

Non-conformance management

This systematic approach classifies deviations from ZDHC requirements based on their direct impact on technical validity and data integrity. It ensures that all laboratory and sampling irregularities are identified, recorded, and resolved through mandatory Corrective Action Plans (CAP) to safeguard the programme’s credibility.

Minor non-conformity

A minor non-conformity is a deviation from established procedures, documentation requirements, or operational practices that does not compromise the validity, reliability, or integrity of test results, laboratory credibility, or overall compliance with ZDHC requirements. Minor non-conformities should be addressed through appropriate corrective actions within the defined timeframe to support continual improvement of laboratory performance.

Major non-conformity

A major non-conformity is a significant failure to meet ZDHC technical, quality, or operational requirements that directly affects, or has the potential to affect, the credibility, accuracy, integrity or traceability of test results or laboratory operations. Major non-conformities require immediate corrective action and resolution to prevent risk to data quality, compliance status, or the integrity of the approved laboratory system.

The quality assurance assesses the severity of the incident and determines whether additional oversight measures, audit or temporary suspension are necessary. Any incident affecting the reliability, accuracy or integrity of In-Check verification shall be formally recorded.

Major non-conformities or systemic or repeated minor non-conformities may lead to suspension.

Technical bulletins

To support the consistent implementation of programme requirements, ZDHC may periodically issue technical bulletins to provide clarifications, additional guidance or updates related to specific activities, processes or technical requirements applicable to approved solution providers.

Technical bulletins are communicated to solution providers via email and are also made available on the Solution Provider Platform for reference and record keeping. These bulletins form part of the operational guidance supporting the implementation of ZDHC requirements and should be reviewed and applied where relevant.