TSS vs NTU

The Sediment Covered Elephant in the Room

Changing environmental legislation creates a challenging environment for frontline environmental regulators. As we move towards a world of ‘fast track consenting,’ decision-making for major projects increasingly shifts from local governments to a more centralized framework, placing greater emphasis on compliance monitoring and enforcement (CME) at the local level. This shift underscores the need to focus on practical and effective environmental management principles.

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Total Suspended Solids (TSS) is a long-established international standard for measuring sediment in water, yet it may not be entirely relevant for New Zealand due to its unique environmental considerations. These include varied water sources, frequent rainfall, diverse geology, high turbidity, and remote monitoring locations. While TSS provides valuable data, its measurement is labor-intensive and costly, which can hinder effective and timely environmental compliance.

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Nephelometric Turbidity Units (NTU), on the other hand, offer a more practical and cost-effective alternative for continuous sediment monitoring. NTU measurements are easier to implement, provide comparable data across different sites, and can be more directly linked to compliance efforts. Importantly, NTU not only measures sediment levels but also gives insights into the contaminants and nutrients carried by the sediment, affecting water quality and biodiversity.

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This paper argues for a shift from traditional TSS measurements to NTU-based monitoring. Emphasizing practical compliance over rigid measurement protocols can save time, money, and resources while improving environmental outcomes. By simplifying monitoring processes, we can enhance our focus on protecting and preserving New Zealand’s water bodies and their biodiversity.

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