Explosives used in the mining industry release nitrate into the environment, causing concerns for the water quality in local river-systems. One way of reducing the nitrate loading into the environment is through a woodchip bioreactor. Water is passed through the bioreactor, where denitrifying microbial communities use the organic carbon from the substrate for energy, together with the nitrate. The efficiency of the denitrification process depends on various factors, including the type of carbon source selected and the temperature. To determine a suitable organic substrate to use in colder environments, column experiments were conducted, comparing different woodchip types. Three columns contained woodchips from pine, spruce and birch. In the fourth column, barley wheat was mixed with pine woodchips. An influent solution was pumped into the columns contained 50 mg/L nitrate-nitrogen. The effluent water was sampled and analysed twice per week for nitrate, nitrite and ammonium concentrations. The pH and alkalinity were analysed weekly to determine that denitrification was taking place. Three column conditions were tested. During the initial period, the columns were kept in 21 °C with a hydraulic residence time (HRT) of 6.3 days. In the following period, the columns were refrigerated at a temperature of 5°C. During the final period, the HRT was lowered to 3.2 days. After a 106-day runtime, it could be concluded that pine woodchips were the most effective substrate for denitrification in 5 °C temperature. The column with pine woodchips removed nitrate efficiently and produced the least amount of by-products and released DOC with a short HRT. The pine woodchips and barley straw column had high nitrite accumulation, and the nitrate removal rate in the birch and spruce woodchip columns was low in 5 °C conditions. / Sprängmedel som används inom gruvindustrin släpper ut nitrat i miljön, vilket kan leda till problem med vattenkvaliteten i lokala vattensystem. Ett sätt att reducera mängden nitrat som släpps ut är genom en bioreaktor med träflis. Vatten passeras genom bioreaktorn, där denitrifierande microbakteriella grupper använder det organiska kolet från substratet för energi, tillsammans med nitratet. Effektiviteten av den denitrifierande processen beror på flertalet faktorer, däribland vilken sorts kolkälla som valts ut och vilken temperatur bioreaktorn håller. För att identifiera ett bra organiskt substrat att använda i kallt klimat genomfördes ett kolumnexperiment som jämförde olika sorters träflis. Tre kolonner innehöll träflis från tall, gran och björk. I en fjärde kolonn blandades kornhalm med träflis från tall. En lösning med koncentrationen 50 mg/L kväve i form av nitrat pumpades in i kolonnerna. Utloppsvattnet från de fyra kolonnerna analyserades två gånger per vecka för koncentration av nitrat, nitrit och ammonium. pH och alkalinitet analyserades varje vecka för att se att denitrifikation skedde. Tre olika förutsättningar testades i kolonnerna. I den första perioden hölls kolonnerna i 21 °C med en hydraulisk uppehållstid på 6,3 dagar. I den följande perioden kyldes kolonnerna till 5 °C. I den sista perioden sänktes uppehållstiden till 3,2 dagar. Efter 106 dagar gick det att fastställa att tall-träflisen var det mest effektiva substratet för denitrifikation i 5 °C. Kolonnen med träflis från tall sänkte nitrathalten i vattnet och producerade minst biprodukter, samt frigjorde organiskt kol även vid kort uppehållstid. Kolonnen med tallflis och kornhalm ackumulerade mycket nitrit, och kolonnerna med träflis från björk och gran hade låga nivåer av nitrat-rening när temperaturen sänktes till 5 °C.

Ammonium-nitrate based explosives (NH4NO3) used within the operations of Kiruna iron ore mine release nitrate (NO3-) into the environment, potentially having adverse effects on local river-systems. One way of reducing NO3- impacts to the environment is through a woodchip denitrifying bioreactor (DBR). Waste rock leachate is collected and passed through the bioreactor, where denitrifying microbial communities reduce NO3- to nitrogen gas (N2) using a carbon energy source. However, the efficiency of the DBR present in Kiruna iron ore mine has declined since the start of its operation leading to lower values of NO3-removal throughout the years.  Denitrification being a temperature dependent process, a heating device was installed to warm up the water prior to the DBR treatment to counterbalance this decrease. The effect of which has been assessed within this thesis. Chemical analyses encompassing NO3-, nitrite (NO2-), ammonium (NH4+), total organic carbon (TOC), phosphorus compounds (tot-P, PO4-P), and bacterial abundance were then investigated along a flowpath in the DBR. Overall, the results have shown that with an increase in temperature prior to the treatment, TOC, tot-P, PO4-P release was improved. Moreover, NO3- removal doubled compared to the previous year. TOC, tot-P and PO4-P are the result of the hydrolysis process, transforming the woodchips in available carbon source and providing nutrients for the bacteria to perform denitrification. Similarly, the bacterial abundance presented a significant increase with temperature. This suggest that both hydrolysis and bacteria growth enhancement with temperature ultimately participated in the improvement of the denitrification reaction. Moreover, a long-lasting effect of temperature on NO3- removal was observed during a following cold period as NO3- removal stayed above 45% after two months without heating. It is suggested that the cost of heating can be reduced by inducing “heat pulse” instead of continuous heating. Adding a heating system prior to treatment represents a promising solution for the future of sustainable mining, particularly for mines located in extreme climates such as Kiruna. / NITREM

Master of Science / Department of Civil Engineering / Alok Bhandari / In the upper Midwest, subsurface tile drainage water is a major contributor of nitrate (NO[subscript]3–N) coming from fertilizers and animal manure. Movement of NO[subscript]3-N through tile drainage into streams is a major concern as it can cause eutrophication and hypoxia conditions, as in the Gulf of Mexico. Denitrifying bioreactors is one of the pollution control strategies to treat contaminated tile drainage water. These bioreactors require four conditions which are: 1) organic carbon source, 2) anaerobic conditions, 3) denitrifying bacteria and 4) influent NO[subscript]3-N. This research focuses on investigating fate of veterinary antibiotics in woodchips commonly used in in-situ reactors. Tylosin (TYL) and sulfamethazine (SMZ) are two veterinary antibiotics which are most commonly used in the United States and can be found in tile water after manure is land applied. Partition coefficients of TYL and SMZ on wood were determined by sorption experiments using fresh woodchips and woodchips from an in situ reactor. It was concluded that the woodchips were an effective means to sorb the veterinary antibiotics leached into the tile water after application of animal manure. Linear partition coefficients were calculated and phase distribution relationships were established for both the chemicals. The fresh woodchips gave inconclusive data but predictions could be made by the information determined in the experiments using woodchips from a ten year old woodchip bioreactor. Desorption was also studied and the likelihood of desorption was predicted using the Apparent Hysteresis Index. Overall, it was found that the old woodchips allowed for quick sorption of both antibiotics. It was also found that SMZ had reversible sorption on old woodchips. Thus, it was concluded that the woodchip bioreactor would not be effective for removal of veterinary antibiotics from tile drainage. More research is required for the fate of TYL and to confirm the conclusion.