Biostimulation and enhancement of pesticide degradation around water abstraction fields

Grundvandsforurening med pesticider er et udbredt miljøproblem og en trussel mod vandforsyningen. Da der sjældent er tale om punktkilder, hvor man kunne yde en særlig rensningsindsats, og pesticidforureningen ofte er blandet op i store voluminer grundvand så koncentrationerne bliver lave, er det vanskeligt at rense hele grundvandsressourcen. Det er naturligvis muligt at rense vandet på selve vandværket, men hvis det forsynes fra flere boringer eller kildepladser, og kun en enkelt boring er forurenet, fortyndes forureningen yderligere på vandværket, så endnu større voluminer af vand skal renses for endnu lavere koncentrationer. På denne baggrund har dette projekt undersøgt mulighederne for at accelerere nedbrydningen af pesticiderne i grundvandsmagasinet omkring den enkelte boring, inden det blandes med uforurenet vand på vej mod vandværket.Grundvand er som regel iltfrit, og de fleste pesticider er vanskeligt nedbrydelige under disse forhold. I PhD-projektet blev nedbrydningen af pesticiderne bentazon, mechlorprop (MCPP) og dichlorprop undersøgt i laboratorieundersøgelser med grundvand og sediment fra et anaerobt grundvandsmagasin ved en aktiv kildeplads. Det var muligt at få bentazon og mechlorprop nedbrudt biologisk ved tilsætning af ilt - selv ved relativt lave koncentrationer (&lt;2 mg/L). Det er navnlig interessant, da dette er første gang, at der er observeret mikrobiel bentazon-nedbrydning med grundvandssediment. Ydermere kunne denne nedbrydning foregå ved lave iltkoncentrationer og over et bredt spektrum af bentazonkoncentrationer.Samlet set har dette PhD-projekt øget vores forståelse af pesticiders nedbrydningsprocesser i grundvandsmagasiner og nogle muligheder for alternative remedieringsstrategier for pesticidforurenede indvindingsboringer.Groundwater contamination by pesticides is a widespread environmental problem and a major threat to drinking water supplies. Diffuse source contamination of groundwater that enters from an extensive area is characterized by low pesticide concentrations (nanogram-microgram per liter) in large volumes of water. It is regarded as one of the major threats to groundwater quality originating from agriculture, roads and railways. These large volumes of water in combination with the low concentration cause difficulties in preventing contamination of drinking water supplies and this is a challenge to develop remediation solutions. Abstraction fields often include several wells. Even if only one of the wells is contaminated, this water mixes with uncontaminated groundwater from the other wells and causes excessive volumes of water to be treated at the waterworks. An alternative approach to the treatment of contaminated groundwater at waterworks is enhanced in situ aerobic bioremediation in the anaerobic aquifers at the contaminated well. This may be achieved by increasing the oxygen content in aquifers with pumping strategies in or around drinking water abstraction wells. With that approach, aerobic groundwater from the upper part of the aquifer may mix with deeper anaerobic groundwater, increasing the oxygen content and creating favorable conditions for biodegradation. However, factors such as oxygen consumption related to organic matter, reduced inorganic species present in the sediment and precipitation of iron followed by the growth of iron bacteria leading to bioclogging reduces the efficiency of bioremediation of contaminated aquifers. The overall scope of this PhD study was to investigate biostimulated degradation potentials of pesticides at low concentrations in groundwater contaminated by diffuse sources in or around water abstraction fields. This approach could lead to more efficient in situ remediation solutions and protection of groundwater as a drinking water supply. Herbicides are generally expected to be difficult to be degraded under anaerobic conditions, but prone to biodegradation under aerobic conditions. Laboratory batch experiments were conducted with anaerobic aquifer material and groundwater collected near an operating drinking water abstraction field to study the potential for stimulating biodegradation of pesticides (bentazone, mecoprop and dichlorprop) at environmentally relevant concentrations (1 μg L-1) by addition of oxygen. Addition of oxygen stimulated mineralization not only at high oxygen concentrations but also at substantially lower concentrations (&lt; 2mg L-1). Biostimulation in terms of enhanced oxygen concentrations around abstraction well fields was found to be a potential remediation solution for pesticides. Furthermore, bentazone mineralization was first time found in aquifer sediments at low oxygen concentrations. Enhanced biostimulation by adding nitrate or nutrients was also seen as potential technologies, however, in the case of nitrate, it was suggested that a mixed oxygen/nitrate system could be used for the contaminants to be degraded under microaerophilic conditions. A literature review regarding degradation of bentazone in topsoils and aquifer sediments supported laboratory experiments that were performed with groundwater and aquifer sediment. Bentazone was degradable in aquifer sediments under aerobic conditions. Furthermore, we were able to transfer bacteria with the capability to degrade bentazone over a wide range of bentazone concentrations from the aquifer material to laboratory experiments. Laboratory microbial studies, aiming to support the observations of transformation of dichlorprop to 4-CPP by different analytic methods at an old landfill, were conducted to investigate anaerobic degradation of 14C-labeled dichlorprop. Concentrations of dichlorprop and 4-CPP with groundwater from the same field site under anaerobic conditions were also measured by analytical chemical analysis. Dichlorprop was recalcitrant in groundwater samples and 4-CPP concentration remained constant during the incubation period. This illustrates the complexity of the field site, characterized by clay-till, with varying redox conditions and residence times providing a higher degradation potential in the field than could be transferred to the laboratory. In conclusion, this PhD has developed our understanding on degradation processes of pesticides in aquifer systems. We have shown that biostimulation by oxygen addition even at relatively low concentrations is a promising remediation technology for groundwater contaminated by pesticides at abstraction well fields. The results of this thesis contribute to our understanding of the development of treatment strategies to protect drinking water wells and suggest an alternative solution to closure of abstraction wells due to pesticide contamination.</p

Yağış sularının sürdürülebilir yönetimi

YAĞIŞ SULARININ SÜRDÜRÜLEBİLİR YÖNETİMİ Kentleşmenin yağış sonrası oluşan yüzey suları üzerinde en önemli etkisi miktar ve kalitede gözlemlenen değişikliklerdir. Kentleşme ile paralel olarak su sızdırmaz alanların artması, yağış sularının yüzeyde kalmasına neden olarak sel baskınlarına, toprak erozyonuna; sızıntı, buharlaşma ve yeraltı suları oluşumunun azalmasına sebep olmaktadır. Kentsel alanlarda yağmur ve kar yağışı sonucu oluşan büyük miktarda yüzey sularının, bu alanlardan mümkün olduğunca kısa bir sürede taşınması için ekolojik olmayan geleneksel drenaj yöntemleri kullanılmaktadır. Bu tezde kentsel gelişimin sel baskınlarına ve su kirliliğine etkilerini azaltmak için kullanılabilecek sürdürülebilir çözümlerin araştırılması amaçlanmıştır. Bu kapsamda, çalışmanın ana hedefi etkin ve sürdürülebilir yağış suları yönetimi uygulamasının ve bunun İsveç, Kristianstad Üniversitesi Kampüsü’nde hayata geçirilme şekillerinin incelenmesidir. Yağış suları yönetim dizisi, yağmur sularının yönetimini çıkış noktasına en yakın alanda önleme, kaynağında, yerinde ve bölgesinde kontrol gibi farklı teknikleri içerdiğinden, seçilen alanda yeşillendirilmiş çatılar, su arkları ve oluşturulan sulak alanlar uygulanmıştır. Yapılan çalışmalar sonucunda, yeşillendirilmiş çatıların diğer en iyi yönetim uygulamaları ile birlikte gözönüne alındıklarında, yağış sonrası oluşan yüzey sularının tutulmasında daha etkili oldukları görülmüştür. Su arkları, yağış sularının toplandığı havzadan taşınması amacıyla tasarlanmıştır. Planlanan parametreler, su arklarının boyutları bakımından çatılardan ve sızdırmayan yüzeylerden gelen su akışını taşıyabilecek durumda olduklarını göstermiştir. Ayrıca, su arkları, yönetim dizisinde sıralanmış sonraki uygulamalara geçmeden önce tahliye debisinin kontrolünün yanı sıra, su kalitesinin iyileştirilmesi için de tasarlanmıştır. Bu çalışmada sulak alan sistemi, tasarlanan su arklarından gelen yağış suyunu son durağı olan Helgean Nehri’ne nakledecek bir yapı olarak düşünülmüştür. Kristianstad Universitesi Kampüsü’nde yapılan bu çalışmada, yağış sularının doğal yöntemlerle yönetiminde sürdürülebilir drenaj sistemlerinin konfor ve estetik görünüm sağlaması ile uygulanabilirliği gösterilmiştir. ABSTRACT SUSTAINABLE URBAN STORMWATER MANAGEMENT The major impact of urbanization on aquatic environment is the changes in the quantity and quality of runoff. Increasing impervious areas cause conversion of rainwater to surface runoff, resulting flooding, soil erosion, together with reduction of infiltration, evaporation, interception and recharge of groundwater. Non-ecological traditional drainage systems are used to remove the large amount of surface water from the urbanized areas as quickly as possible. This thesis investigates sustainable solutions to reduce the impacts of urban development on flooding and water pollution. In this context, the main aim of this study is to analyze the effective sustainable stormwater practices and their application to Sweden, Kristianstad University Campus. As stormwater treatment train provides different techniques such as prevention, source, site and regional control to manage the rainwater as close as to its source; green roofs, swales and constructed wetland have been applied for the selected area. It was found that green roofs are more effective if employed together with other best management practices to detain stormwater successfully. Swales have been designed for conveying the rainwater from the catchment area. The designed parameters showed that the dimensions of swales are proper to handle the surface runoff from roofs and hard surfaces. Apart from controlling the discharge flow rate, swales have been designed to improve the water quality before reaching the next stormwater management practices. The wetland system has been considered as a conveyance of rainwater coming from the designed swales to the last destination, river Helgean. The Kristianstad University Campus study showed the applicability of sustainable drainage systems to manage stormwater in Nature’s way with improving amenity and aesthetic way

Behçet's syndrome / AIDS / cerebral toxoplasmosis: an unusual association

Few cases of AIDS associated to manifestations suggesting Behçet's syndrome have been reported. This case is of a young married woman who presented, during a period of 7 years, clinical manifestations consistent with the late diagnosis of Behçet's syndrome, when she developed recurrent lymphomonocytic meningoencephalitis. At this time, she was found to be infected by HIV-1. Immunosupressive doses of glucocorticoid produced an unsatisfactory response and she evolved to death due to CNS toxoplasmosis. The latter diagnosis was presumed on the basis of magnetic resonance imaging findings and proved by necropsy after her third hospital stay. One of the factors hindering the appropriate diagnosis was the low level of CD4 and the CD4/CD8 ratio, sometimes observed in active Behçet's syndrome and higher than those observed in patients with this severe opportunistic infection. No information about the exact period of time she had been infected with HIV-1 is available. So, we do not know whether both diseases were overlor, if the patient, infected by HIV-1, developed an unusual clinical feature consistent with Behçet's Behçet's syndrome, and subsequently evolved to AIDS