Biomedical subjects

M G Healy

Publications and source records attributed to M G Healy.

6 recordsLinked to original sources

PubMed2006

Treatment of dairy wastewater using constructed wetlands and intermittent sand filters.

In Ireland, the most common method of disposal of dairy parlour washings is by land spreading. This treatment method has numerous problems, namely high-labour requirements and the potential for eutrophication of surface and ground waters. Constructed wetlands are commonly used for treatment of secondary municipal wastewaters and they have been gaining popularity for treatment of agricultural wastewaters in Ireland. Intermittent sand filtration may offer an alternative to traditional treatment methods. As well as providing comparable treatment performance, they also have a smaller footprint, due to the substantially higher organic loading rates that may be applied to their surfaces. This paper discusses the performance and design criteria of constructed wetlands for the treatment of domestic and agricultural wastewater, and sand filters for the treatment of domestic wastewater. It also proposes sand filtration as an alternative treatment mechanism for agricultural wastewater and suggests design guidelines.

Animals↗

PubMed2006

Performance of a stratified sand filter in removal of chemical oxygen demand, total suspended solids and ammonia nitrogen from high-strength wastewaters.

A stratified sand filter column, operated in recirculation mode and treating synthetic effluent resembling high-strength dairy wastewaters was studied over a 342-d duration. The aim of this paper was to examine the organic, total suspended solids (TSS) and nutrient removal rates of the sand filter, operated in recirculation mode, under incrementally increasing hydraulic and organic loading rates and to propose a field filter-sizing criterion. Best performance was obtained at a system hydraulic loading rate of 10 L m(-2) d(-1); a higher system hydraulic loading rate (of 13.4 L m(-2) d(-1)) caused surface ponding. The system hydraulic loading rate of 10 L m(-2) d(-1) gave a filter chemical oxygen demand (COD), TSS, and total kjeldahl nitrogen (TKN) loading rate of 14, 3.7, and 2.1 g m(-2) d(-1), respectively, and produced consistent COD and TSS removals of greater than 99%, and an effluent NO(3)-N concentration of 42 mg L(-1) (accounting for an 86% reduction in total nitrogen (Tot-N)). As the proportional surface area requirement for the sand filter described in this study is less than the recommended surface area requirement of a free-water surface (FWS) wetland treating an effluent of similar quality, it could provide an economic and sustainable alternative to conventional wetland treatment.

Dairying↗

PubMed2005

Nitrification in a vertically moving biofilm system.

A laboratory continuous feed biofilm reactor, comprising a bulk fluid reactor, a biofilm plastic module, a feed tank, and pneumatic devices and controls, was operated for a total period of 257 days, including seeding time, to treat domestic-strength synthetic wastewater under increasing ammonium nitrogen (NH(4)(+)--N) loading rates, ranging from 0.17+/-0.01 (0.71+/-0.06 gm(-2)d(-1)) to 0.70+/-0.02 kgm(-3)d(-1) (2.9+/-0.1 gm(-2)d(-1)). The biofilm plastic module was moved vertically in and out of the wastewater in continuous cycles. The maximum NH(4)(+)-N removal rate was reached during the maximum loading phase, when a NH(4)(+)--N loading rate of 0.70+/-0.02 kgm(-3)d(-1) (2.9+/-0.1 gm(-2)d(-1)) was applied to the system. During this loading period, the average NH(4)(+)--N removal rate was 0.30+/-0.10 kgm(-3)d(-1) (1.30+/-0.40 gm(-2)d(-1)).

Ammonium Chloride↗

PubMed2005

Organic carbon removal and nitrification of high strength wastewaters using stratified sand filters.

The current practice of spray irrigation of dairy parlour wastewaters is laborious and time consuming. Intermittent sand filtration systems may offer an alternative to spray irrigation when designed to remove organic carbon, nitrogen, phosphorus, coliforms and viruses from such wastewaters to allow discharge of the final effluent directly into receiving waters without damage to the environment. In this study two instrumented stratified sand filter columns (0.425 and 0.9 m deep, and both 0.3 m in diameter) were intermittently loaded for 439 days with synthetic dairy parlour washings at a number of hydraulic and organic loading rates. At a biochemical oxygen demand (BOD) loading of 22 g m(-2) d(-1), over 92% of the BOD and suspended solids in the wastewater was removed in the two filters and nitrification was complete. The 0.9 m column had a sustained ability to adsorb the influent phosphorus during the study period; however, the phosphorus adsorption capacity of the 0.425 m column began to decrease after approximately 30 days. Biomass, comprising hydrated extracellular polymers (exopolymers) and living and dead cells, accumulated in the 0.9 m column; it was assessed by sodium bromide tracer studies and by variations in the sand volumetric water contents using time domain reflectometry (TDR). The biomass growth increased the retention time of the wastewater in the filter media, and occurred mainly at the top of the first sand layer. Intermittent stratified sand filters appear to offer an effective and sustainable treatment process for the removal of BOD from high-strength wastewaters, and for the complete nitrification of ammonium.

Adsorption↗

PubMed2005

The efficiency of a sequencing batch biofilm reactor in organic carbon and phosphorus removal.

A laboratory sequencing batch biofilm reactor (SBBR), operated for a period of 158 days, was used to treat domestic-strength synthetic effluent. The biofilm reactor comprised a bulk fluid reactor, a biofilm plastic module, a synthetic wastewater feed tank, and pneumatic devices with pneumatic controls. The reactor cycle time was 8 h, and its operation consisted of five phases: feeding (59 min), mixing (1 min), anoxic/anaerobic (3 h), aerobic (3 h), and settling (1 h). At total chemical oxygen demand (CODT) loading rates of 8.8 g CODT m(-2) d(-1) and 1.2 kg CODT m(-3) d(-1), expressed in terms of the plastic module surface area and reactor volume, respectively, the SBBR had average removal rates of 8.3 g CODT m(-2) d(-1) and 1.1 kg CODT m(-3) d(-1), or 94%. Total orthophosphorus (PO4-PT) and filtered orthophosphorus (PO4-PF) removals were 44% and 50%, respectively.

Biofilms↗

PubMedDate not supplied

Recirculating sand filters for treatment of synthetic dairy parlor washings.

Land-spreading and spray irrigation are the most widely used practices for the disposal of dairy wastewaters in Ireland but in some cases there can be problems due to contamination of surface and ground water. The use of intermittent sand filtration has been suggested as an alternative treatment process. However, a single pass through a sand filter limits denitrification because of the absence of reducing conditions following nitrification and the lack of an available carbon source. This leads to poor total nitrogen (TN) reduction and an effluent that is high in nitrate nitrogen (NO3-N). This paper follows a previous paper in which two instrumented stratified sand filter columns (0.9 and 0.425 m deep, and both 0.3 m in diameter) were intermittently loaded with synthetic dairy parlor washings at a number of hydraulic loading rates, leading to a TN reduction of 27 to 41%. In the present study, under a chemical oxygen demand (COD) of 23.4 g m(-2) d(-1), the TN was reduced by 83.2% when three-quarters of the sand filter effluent was recirculated through an anoxic zone. This produced an effluent NO3-N concentration of 60 mg L(-1). With recirculation, the improvement in the removal of organic matter and ammonia N (NH4-N) is minimal. Recirculating sand filters appear to offer a mechanically simple and effective method for the removal of nitrogen from dairy parlor effluents and are a significant improvement over a single-pass sand filter.

Animals↗