A novel hybrid coagulation-constructed wetland system for the treatment of dairy wastewater

peer-reviewedConstructed wetlands (CWs) are a cost-effective and sustainable treatment technology that may be used on farms to treat dairy wastewater (DWW). However, CWs require a large area for optimal treatment and have poor long-term phosphorus removal. To overcome these limitations, this study uses a novel, pilot-scale coagulation-sedimentation process prior to loading CWs with DWW. This hybrid system, which was operated on an Irish farm over an entire milking season, performed well at higher hydraulic loading rates than conventional CWs, and obtained removal efficiencies ≥99 % for all measured water quality parameters (chemical oxygen demand, total nitrogen and phosphorus, total suspended solids and turbidity), which complied with EU directives concerning urban wastewater treatment. Overall, the hybrid coagulation-CW is a promising technology that requires a smaller area than conventional CWs and minimal operator input, and produces high effluent quality

Design and modeling of reservoir operation strategies for sediment management

Appropriate operation strategies that allow for sediment flushing and sluicing (sediment routing) can reduce rapid storage losses of (hydropower and water-supply) reservoirs. In this study we have shown, using field observations and computational models, that the efficiency of these operations increases when utilizing dynamics of flow and sediment movement. For instance, operating at a minimum level during the sediment-laden high flows at the start of the flood season, and a rapid short draw-down flushing event later-on, allows much of the incoming sediments to pass the reservoir. Hence, operations can be more effective when using the dynamics of the high river flows, arrival of suspension peaks, and timing of emptying and filling of the reservoir.Hydraulic EngineeringCivil Engineering and Geoscience

A novel hybrid coagulation-constructed wetland system for the treatment of dairy wastewater

Constructed wetlands (CWs) are a cost-effective and sustainable treatment technology that may be used on farms to treat dairy wastewater (DWW). However, CWs require a large area for optimal treatment and have poor long-term phosphorus removal. To overcome these limitations, this study uses a novel, pilot-scale coagulation-sedimentation process prior to loading CWs with DWW. This hybrid system, which was operated on an Irish farm over an entire milking season, performed well at higher hydraulic loading rates than conventional CWs, and obtained removal efficiencies ≥99 % for all measured water quality parameters (chemical oxygen demand, total nitrogen and phosphorus, total suspended solids and turbidity), which complied with EU directives concerning urban wastewater treatment. Overall, the hybrid coagulation-CW is a promising technology that requires a smaller area than conventional CWs and minimal operator input, and produces high effluent quality.The authors are grateful to Teagasc for the award of a Walsh Fellowship to the first author [grant number: RMIS-0386]. The authors appreciate the help of technical staff: Adrian Hawe; Seamus McShane, JohnPaul Murphy & Tomas Condon (Teagasc Moorepark), and Denis Brennan (Teagasc Johnstown Castle).peer-reviewe

Effects of substrate stress and light intensity on enhanced biological phosphorus removal in a photo-activated sludge system

Photo-activated sludge (PAS) systems are an emerging wastewater treatment technology where microalgae provide oxygen to bacteria without the need for external aeration. There is limited knowledge on the optimal conditions for enhanced biological phosphorus removal (EBPR) in systems containing phosphate accumulating organisms (PAOs) and microalgae. The aim of this research was to study the effects of substrate composition and light intensity on the performance of a laboratory-scale EBPR-PAS system. First, a EBPR model was developed to study the effect of organic carbon (COD), inorganic carbon (HCO3) and ammonium-nitrogen (NH4-N) in nitrification deprived conditions on phosphorus (P) removal. Based on the mathematical model, two different synthetic wastewater compositions of COD:HCO3:NH4-N of 10:20:1 and 10:10:4 were examined in laboratory reactors. The performance of the system was also investigated at different light intensities: 87.5, 175, 262.5, and 350 µmol m-2 sec-1. At a ratio of 10:20:1, the system performed poorly, potentially due to an insufficient supply of NH4-N for PAOs growth. At a ratio of 10:10:4, the performance improved significantly as microalgal growth was balanced by reducing inorganic carbon, and was able to operate without external aeration. Under this mode of operation, the net removal of P was 10.33 ±1.45 mg/l and the total P uptake was 27.8 ±1.8 mg/l (94.7±5.7 % P removal). No significant variation was observed in the reactor performance for different light intensities, suggesting that the system is resilient against fluctuations in light intensity.The authors are grateful to Nuffic for the award of Netherlands Fellowship Program (NFP) to the first author. The authors appreciate the help of technical staff: Berend Lolkema and Peter Heerings (IHE-Delft)peer-reviewe

Effects of substrate stress and light intensity on enhanced biological phosphorus removal in a photo-activated sludge system

Photo-activated sludge (PAS) systems are an emerging wastewater treatment technology where microalgae provide oxygen to bacteria without the need for external aeration. There is limited knowledge on the optimal conditions for enhanced biological phosphorus removal (EBPR) in systems containing phosphate accumulating organisms (PAOs) and microalgae. The aim of this research was to study the effects of substrate composition and light intensity on the performance of a laboratory-scale EBPR-PAS system. First, a EBPR model was developed to study the effect of organic carbon (COD), inorganic carbon (HCO3) and ammonium-nitrogen (NH4-N) in nitrification deprived conditions on phosphorus (P) removal. Based on the mathematical model, two different synthetic wastewater compositions of COD:HCO3:NH4-N of 10:20:1 and 10:10:4 were examined in laboratory reactors. The performance of the system was also investigated at different light intensities: 87.5, 175, 262.5, and 350 µmol m-2 sec-1. At a ratio of 10:20:1, the system performed poorly, potentially due to an insufficient supply of NH4-N for PAOs growth. At a ratio of 10:10:4, the performance improved significantly as microalgal growth was balanced by reducing inorganic carbon, and was able to operate without external aeration. Under this mode of operation, the net removal of P was 10.33 ±1.45 mg/l and the total P uptake was 27.8 ±1.8 mg/l (94.7±5.7 % P removal). No significant variation was observed in the reactor performance for different light intensities, suggesting that the system is resilient against fluctuations in light intensity.The authors are grateful to Nuffic for the award of Netherlands Fellowship Program (NFP) to the first author. The authors appreciate the help of technical staff: Berend Lolkema and Peter Heerings (IHE-Delft