Why Monitor for Wastewater Contamination?
Effective and economically viable monitoring techniques, that inform coastal managers of the spatial and temporal variation in the intensity and composition of wastewater discharge into coastal waters, are key to the success of these pollution reduction efforts. Domestic wastewater contains high organic loads, and often a variety of toxic chemicals and substances, such as plastics and heavy metals. Ultimately, these chemicals impair the health and future well-being of both humans and nature. Detailed monitoring information is essential to managers and policy makers, as it allows them to:
- Focus limited resources in areas that are most heavily affected,
- Understand the spatial and temporal extent and variation of pollution threats,
- Understand and communicate if the contaminants pose threats to both humans and nature,
- Identify hotspots of contaminants,
- Assess the effectiveness of enacted interventions, and ultimately,
- Inform future actions and decisions using adaptive-based management.
How do we currently monitor wastewater contamination?
There are currently a diverse set of monitoring techniques for wastewater discharge. These techniques can be broken down into two general categories: a) Proportion of Discharge Water Treated: percent and total flow of industrial and household discharge that is treated versus non-treated; and b) Performance of Treatment: spatial and temporal extent of wastewater derived contaminants, and their impacts on biological oxygen demand in water coming out of treatment plants, as well as in surrounding aquatic ecosystems. The former category gives an idea of how much untreated wastewater enters the system, while the latter provides an evaluation of the performance of wastewater treatment in the area of focus. Hydrologists and civil engineers work together to generate the first estimate, while environmental scientists and modelers, working both in the field and in the lab, combine their efforts to provide the second estimate.
When monitoring performance, what is measured typically differs when assessing threats to humans versus nature. Traditionally, public health threats are quantified by indicator microorganisms, such as fecal coliform or total count of heterotrophic bacteria, to infer presence of human pathogens, human feces, and process change (e.g., increased oxygen demand) in wastewater discharge; or water receiving wastewater discharge. For threats to nature, scientists have focused on monitoring nutrient loads that can change due to increasing wastewater discharge, primarily nitrogen, phosphorus, and oxygen concentrations in the water column. More recently, there has been expanded interest in measuring factors that threaten both humans and nature: toxic chemicals such as heavy metals, hormones, pharmaceuticals, industrial by-products, and plastics. Thus, measuring extent and impact of wastewater contamination involves measuring a large number of response variables – a list that is expanding over time.
What limits effective monitoring of the extent of wastewater contamination and its potential impacts on coastal ecosystems?
While the technological know-how (in the scientific literature) does not generally limit our ability to measure a great number of chemicals and pathogens that occur in waters experiencing increasing wastewater discharge; cost, human resources, materials, and lab supplies, do. Other factors that limit effective monitoring and better treatment of wastewater discharge include:
- Most countries fail to integrate monitoring data at a national level.
- Few countries collect data at on-site wastewater treatment (septic systems).
- Most countries have only a small percentage of industries use permits to discharge; and those that do are rarely monitored.
- Monitoring of collected and recorded data from local areas is challenging due to differences in reporting and storage locations, making it hard to combine data to assess temporal and spatial trends.
- When wastewater contamination is monitored, most of the time variables are measured that predict impacts on human health, rather than environmental health. Thus, only a small subset of contaminants is measured.