Groundwater is considered as the main source of water supply for drinking, irrigation and municipal uses in Palestine. Recent publications revealed that most of groundwater wells in the Gaza Strip are contaminated with high nitrate concentrations, and unfit for potable and agricultural uses.
The nitrate in groundwater with high concentrations is mainly resulted from point sources such as sewage disposal systems and livestock facilities, and from nonpoint sources such as fertilized lands, and gardens, or from naturally occurring sources of nitrogen. Groundwater contamination by excessive nitrate poses significant public health problems and have caused those shutdown of ground wells as a main water sources.
The objective of this study is to evaluate and examine the feasibility of biological denitrification process to treat or reduce the nitrate-rich in groundwater using whey as an external carbon sources. Whey, a dairy waste product, will be added to the bioreactor to provide an external carbon source for heterotrophic denitrifiers.
To achieve the main objective, a lab-scale bioreactor was designed, assembled and run in both batch and continuous modes. Operational results using batch tests revealed an optimum COD/NO3--N ratio of 7.2 with a maximum specific denitrification rate of 14.61 (mg NO3--N/gMLSS.hr). This C/N ratio was used to evaluate the performance of the system in continuous mode to obtain all the required operational parameters. Different influent nitrate-nitrogen concentrations were used in the study with different nitrate-nitrogen loading to study the effect of hydraulic retention time (HRT), nitrate loading, mixed liquor suspended solids effects on the nitrate removal efficiency in additional to the reactor removal capacity. Physical, chemical and biological parameters were determined according to the American Public Health Standards Association (APHA).
The maximum denitrification efficiency was achieved and became constant at 5 hours HRT for different nitrate influent concentrations.
Further treatment for the effluent is needed to reduce turbidity, bacterial numbers, and to increase the dissolved oxygen concentration in the effluent to comply with local drinking water quality standards.