Assessing the Ecological Relevance of Organic Discharge Limits for Constructed Wetlands by Means of a Model-Based Analysis

Abstract

Polder watercourses within agricultural areas are affected by high chemical oxygen demand (COD) and biological oxygen demand (BOD 5 ) concentrations, due to intensive farming activities and runoff. Practical cases have shown that constructed wetlands (CWs) are eco-friendly and cost-effective treatment systems which can reduce high levels of organic and nutrient pollution from agricultural discharges. However, accumulated recalcitrant organic matter, originated by in-situ sources or elements of CWs (i.e., plants or microbial detritus), limits the fulfilment of current COD discharge threshold. Thus, to evaluate its relevance regarding rivers ecosystem health preservation, we analysed the response of bio-indicators, the Multimetric Macroinvertebrate Index Flanders (MMIF) and the occurrence of organic pollution sensitive taxa towards organic pollutants. For this purpose, statistical models were developed based on collected data in polder watercourses and CWs located in Flanders (Belgium). Results showed that, given the correlation between COD and BOD 5 , both parameters can be used to indicate the ecological and water quality conditions. However, the variability of the MMIF and the occurrence of sensitive species are explained better by BOD 5 , which captures a major part of their common effect. Whereas, recalcitrant COD and the interaction among other physico-chemical variables indicate a minor variability on the bio-indicators. Based on these outcomes we suggest a critical re-evaluation of current COD thresholds and moreover, consider other emerging technologies determining organic pollution levels, since this could support the feasibility of the implementation of CWs to tackle agricultural pollution.

Agronomic and Environmental Performance of Lemnaminor Cultivated on Agricultural Wastewater Streams—A Practical Approach

“…A potential element responsible for the better performance of PM could be humic substances. Humic substances have been reported in wastewater from piggery treatment facilities, such as the one investigated in the present study [42]. Dissolved organic material can also be present in PP, which is released by the physicochemical degradation of the fish feed and the fish excretions, or by microorganisms [43,44].…”

Life Cycle Assessment of Electrodialytic Technologies to Recover Raw Materials from Mine Tailings

“…The BOD 5 presents the second highest impacts (2.08 × 10 −3 kg/t ore), meaning a decrease in the amount of oxygen consumed, by aerobic biological organisms, to decompose the organic matter in 5 days. An excessive microbial activity causes a reduction in the quantity of oxygen in the water, which may foment the growth of anaerobic organisms and decay the development of other existing communities [39].…”

Advances in Ecological Water System Modeling: Integration and Leanification as a Basis for Application in Environmental Management

“…Moreover, models can be used for exploration purposes [18] and trade-off analysis [19], and environmental impact assessment [20] to inspire stakeholders and to support decision-making for policy developers. The effect of tipping points and environmental standards [21] can be analysed via models, as well as the uncertainty of assessment methods [22,23], or effects of particular choices made during assessments [24]. Models can also contribute to the leanification of data collection [5] and interpretation of data [25].…”