Anne-Grete Buseth Blankenberg

Senior Research Scientist

(+47) 416 97 737
Anne-Grete.Blankenberg@nibio.no

Place
Ås F20

Visiting address
Fredrik A. Dahls vei 20, 1430 Ås

Abstract

This study describes the first Norwegian microbial source tracking (MST) approach for water quality control and pollution removal from catchment run-off in a nature-based treatment system (NBTS) with a constructed wetland. The applied MST tools combined microbial analyses and molecular tests to detect and define the source(s) and dominant origin(s) of faecal water contamination. Faecal indicator bacteria Escherichia coli and host-specific Bacteroidales 16 s rRNA gene markers have been employed. The study revealed that the newly developed contribution profiling of faecal origin derived from the Bacteroidales DNA could quantitatively distinguish between human and non-human pollution origins. Further, the outcomes of the MST test have been compared with the results of both physicochemical analyses and tests of pharmaceutical and personal care products (PPCPs). A strong positive correlation was discovered between the human marker and PPCPs. Gabapentin was the most frequently detected compound and it showed the uppermost positive correlation with the human marker. The study demonstrated that the NBTS performs satisfactorily with the removal of E. coli but not PPCPs. Interestingly, the presence of PPCPs in the water samples was not correlated with high concentrations of E. coli. Neither has the latter an apparent correlation with the human marker.

Abstract

Water quality problems in Norway are caused mainly by high phosphorus (P) inputs from catchment areas. Multiple pollution sources contributes to P inputs into watercourses, and the two main sources in rural areas are agricultural runoff and discharge from on-site wastewater treatment systems (OWTSs). To reduce these inputs, Constructed wetlands (CWs) treating catchment runoff have been implemented in Norway since early 1990s. These CWs have been proven effective as supplements to agricultural best management practices for water quality improvements and therefore there are more than 1000 CWs established in Norway at present. This study aims to present some overall data on the present status of CWs treating catchment runoff in Norway, and in particular recent results of source tracking and retention of sediments and total phosphorus (TP) in a model, full-scale, long-term operated CW, which in practice treats runoff from a typical rural catchment with pollution from both point and diffuse sources. Nutrient contributions from agricultural runoff and OWTSs have been quantified in eight catchments, while the source tracking and retention of sediments and P has been studied in the model CW. P runoff in the catchments was largely affected by precipitation and runoff situation, and varied both throughout the year (every single year) and from one year to another. Annual TP contribution that origins from OWTSs was in general limited, and only 1 % in the catchment of the model CW. Monthly contribution, however, was higher than 30 % during warm/dry season, and cold months with frost season. For the purpose of source tracking study, faecal indicator bacteria (reported in terms of Escherichia coli - E. coli) and host-specific 16S rRNA gene markers Bacteroidales have been applied. High E.coli concentrations were well associated with high TP inputs into waterbodies during dry or/and cold season with little or no agriculture runoff, and further microbial source tracking (MST) tests proved human contribution. There are considerable variations in retention of sediments and TP in the CW between the years, and the annual yearly retention was about 38 % and 16 %, respectively. During the study period, the average monthly retention of sediments and TP was 54 % and 32 %, respectively. E. coli concentrations were also reduced in water passing the CW. The study confirmed that runoff from agricultural areas is the main P source in watercourses, however, discharges from OWTS can also be of great importance for the water quality, especially during warm/dry- and cold/frosty periods. Small CWs treating catchment runoff contribute substantially to the reduction of sediments, TP and faecal indicator bacteria transport into water recipients.

Abstract

Norwegian constructed wetlands (CWs) that treat domestic wastewater are classified as horizontal subsurface flow constructed wetlands (HSFCWs). Over the years of continuous performance, the HSFCWs operating under cold climate conditions have shown a high and stable treatment efficiency with regard to the removal of organic matter (>90 % BOD), nutrients (>50 % N and >90 % P) and microbes (>99 % bacteria). The majority of Norwegian HSFCWs are categorised as small (<50 pe) on-site, decentralised wastewater treatment systems. The Norwegian systems consist of three fundamental elements: a septic tank, a pre-filter (i.e. an aerobic vertical flow biofilter) and a horizontal flow saturated filter/wetland bed. The first, primary treatment step begins in the septic tank from which effluents are pre-treated in the second step occurring in the pre-filter/biofilter section and further in the third, final step taking place in the filter bed/HSFCW. The first and third treatment steps are quite common in systems with CWs, but the pre-treatment in biofilter(s) is mainly known from Norway. The main purpose of using the pre-treatment phase is to supply air during the cold season, to enhance nitrification processes, and to reduce the load of organic matter before entering the filter/wetland bed. If constructed and maintained correctly, the biofilters alone can remove 90 % BOD and 40 % N. Various filter/CW beds have been introduced for treatment of domestic wastewater (as complete or source-separated streams) in Norway, but the most common feature is the use of specific filter media for high phosphorus (P) removal. A few Norwegian municipalities also have limits with respect to nitrogen (N) discharge, but the majority of municipalities use 1.0 mg P/l as the discharge limit for small wastewater treatment systems. This particular limit affects the P retention lifetime of the filter media, which varies from system to system depending on the filter media applied, the type of wastewater treated, and the system design and loading rates. An estimated lifetime of filter media with regard to P removal is approximately 15–18 years for a filter/CW bed of a single household. After completing the lifetime, the filter media is excavated and replaced with new/fresh materials, allowing the system to operate effectively for another lifespan. Since the exploited media are P-rich materials, the main intention is their reuse in a safe and hygienic way, in which P could be further utilised. Therefore, the Norwegian systems can represent a complex technology combining a sustainable technique of domestic wastewater treatment and a bio-economical option for filter media reuse. This is a quite challenging goal for reclamation and recycling of P from wastewater. Thus, there are some scenarios of reusing the P-rich filter media as a complementary P fertiliser, a soil amendment or a conditioner, provided the quality is acceptable for utilisation in agriculture. Alternatively, the filter media could be reused in some engineering projects, e.g. green roof technology, road screening or construction of embankments, if the quality allows application in the environment. The core aspect of the reuse options is the appropriate quality of the filter media. As for the theoretical assumption, it should not be risky to reuse the P-rich media in agriculture. In practice, however, the media must be proven safe for human and environmental health prior to introducing into the environment.

Abstract

Nutrients for food production are traditionally extracted from natural resources, most importantly as nitrogen from the air, and phosphorous from limited mineral resources. They can also be recovered and recycled from human waste products. There is generally a low P status in the world’s soils, while Norwegian soils are rich in phosphorous. Most recyclable P is in human and animal waste products as wastewater and manure, but also municipal solid waste and more recently, organic waste contain a considerable amount of P that ideally can be utilized.

Abstract

Elevated nutrient concentrations in streams in the Norwegian agricultural landscape may occur due to faecal contamination. Escherichia coli (E. coli) has been used conventionally as an indicator of this contamination; however, it does not indicate the source of faecal origin. This work describes a study undertaken for the first time in Norway on an application of specific host-associated markers for faecal source tracking of water contamination. Real-time quantitative polymerase chain reaction (qPCR) on Bacteroidales host-specific markers was employed for microbial source tracking (MST) to determine the origin(s) of faecal water contamination. Four genetic markers were used: the universal AllBac (Bacteroidales) and the individual specific markers BacH (humans), BacR (ruminants) and Hor-Bac (horses). In addition, a pathogenicity test was carried out to detect the top seven Shiga toxin-producing E. coli (STEC) serogroups. The ratio between each individual marker and the universal one was used to: (1) normalise the markers to the level of AllBac in faeces, (2) determine the relative abundance of each specific marker, (3) develop a contribution profile for faecal water contamination and (4) elucidate the sources of contamination by highlighting the dominant origin(s). The results of the qPCR MST analyses indicated the actual contributions of humans and animals to faecal water contamination. The pathogenicity test revealed that water samples were STEC positive at a low level, which was in proportion to the concentration of the ruminant marker. The outcomes were verified statistically by coupling the findings of major contamination sources with observations in the field regarding local land use (residential or agricultural). Furthermore, clear correlations between the human marker and E. coli counts as well as the ruminant marker and STEC quantity in faecally contaminated water were observed. The results of this study have the potential to help identify sources of pollution for targeted mitigation of nutrient losses.