ABSTRACT
The change in nitrogen balance causes many environmental and socioeconomic impacts. In relation to food production and nitrogen release in wastewater systems, wastewater and sludge discharge and mineral fertilizer use intensify nitrogen imbalance of a region. The replacement of mineral fertilizer by nitrogen from treated wastewater, biosolids, and treated urine is a promising alternative. This work presents a model to support decision taking for the management of reactive nitrogen flows in wastewater systems based on system dynamics. Six scenarios were simulated for nitrogen flows in wastewater systems and related components.
Subject(s)
Decision Support Systems, Management , Fertilizers/analysis , Models, Theoretical , Nitrogen/analysis , Waste Disposal, Fluid/methods , Wastewater/chemistry , Fertilizers/economics , Waste Disposal, Fluid/economicsABSTRACT
This study investigates the effects of chlorothalonil (CLT) on chemical oxygen demand (COD) and dissolved organic carbon (DOC) in pilot-scale horizontal subsurface flow constructed wetlands (HSSFCW) planted with Phragmites australis. Physicochemical parameters of influent and effluent water samples, microbial population counting methods and statistical analysis were used to evaluate the influence of CLT on organic matter removal efficiency. The experiments were conducted on four planted replicate wetlands (HSSFCW-Pa) and one unplanted control wetland (HSSFCW-NPa). The wetlands exhibited high average organic matter removal efficiencies (HSSFCW-Pa: 80.6% DOC, 98.0% COD; HSSFCW-NPa: 93.2% DOC, 98.4% COD). The addition of CLT did not influence organic removal parameters. In all cases CLT concentrations in the effluent occurred in concentrations lower than the detection limit of the analytical method. Microbial population counts from HSSFCW-Pa showed significant correlations among different microbial groups and with different physicochemical variables. The apparent independence of organic matter removal and CLT inputs, along with the CLT depletion observed in effluent samples demonstrated that HSSFCW are a viable technology for the treatment of agricultural effluents contaminated with organo-chloride pesticides like CLT.