ABSTRACT
Tannery operations consist of converting raw animal skins into leather through a series of complex water- and chemically-intensive batch processes. Even when conventional primary treatment is supplemented with chemicals, the wastewater requires some form of biological treatment to enable the safe disposal to the natural environment. Thus, there is a need for the adoption of low cost, reliable, and easy-to-operate alternative secondary treatment processes. This paper reports the findings of two pilot-scale wetlands for the secondary treatment of primary effluents from a full tannery operation in terms of resilience (i.e., ability to produce consistent effluent quality in spite of variable influent loads) and reliability (i.e., ability to cope with sporadic shock loads) when treating this hazardous effluent. Areal mass removal rates of 77.1 g COD/m2/d, 11 g TSS/m2/d, and 53 mg Cr/m2/d were achieved with a simple gravity-flow horizontal subsurface flow unit operating at hydraulic loading rates of as much as 10 cm/d. Based on the findings, a full-scale wetland was sized to treat all the effluent from the tannery requiring 68% more land than would have been assumed based on literature values. Constructed wetlands can offer treatment plant resilience for minimum operational input and reliable effluent quality when biologically treating primary effluents from tannery operations.
Subject(s)
Chromium , Tanning , Waste Disposal, Fluid/methods , Water Pollutants, Chemical , Wetlands , Adsorption , Industrial Waste , Pilot ProjectsABSTRACT
The Chaco-Pampean plain, Argentina, is a vast geographical unit (1,000,000 km²) affected by high arsenic (As) concentrations in universal oxidizing groundwater. The socio-economic development of the region is restricted by water availability and its low quality caused by high salinity and hardness. In addition, high As and associated trace-elements (F, U, V, B, Se, Sb, Mo) concentrations of geogenic origin turn waters unsuitable for human consumption. Shallow groundwater with high As and F concentrations (ranges: <10-5300 µg As/L; 51-7,340 µg F/L) exceeding the WHO guideline values (As: 10 µg/L; F: 1,500 µg/L) introduces a potential risk of hydroarsenicism disease in the entire region and fluorosis in some areas. The rural population is affected (2-8 million inhabitants). Calcareous loess-type sediments and/or intercalated volcanic ash layers in pedosedimentary sequences hosting the aquifers are the sources of contaminant trace-elements. Large intra and interbasin variabilities of trace-element concentrations, especially between shallow and deep aquifers have been observed. All areas of the Chaco-Pampean plain were affected in different grades: the Chaco-Salteña plain (in the NNE of the region) and the northern La Pampa plain (in the center-south) have been shown the highest concentrations. The ranges of As and F contents in loess-sediments are 6-25 and 534-3340 mg/kg, respectively in the Salí River basin. Three key processes render high As concentrations in shallow aquifers: i) volcanic glass dissolution and/or hydrolysis and leaching of silicates minerals hosted in loess; ii) desorption processes from the surface of Al-, Fe- and Mn-oxi-hydroxides (coating lithic fragments) at high pH and mobilization as complex oxyanions (As and trace elements)in Na-bicarbonate type groundwaters; and iii) evaporative concentration in areas with semiarid and arid climates. Local factors play also an important role in the control of high As concentrations, highly influenced by lithology-mineralogy, soils-geomorphology, actual climate and paleoclimates, hydraulic parameters, and residence time of groundwaters.
Subject(s)
Arsenic/analysis , Trace Elements/analysis , Argentina , Groundwater/chemistry , Water Pollutants, Chemical/analysisABSTRACT
Programa de la Reunión de Consulta. Síntesis del programa ISARM. Documentos de trabajo de la reunión. Inventario de Acuíferos transfronterizos europeos. El sistema Acuífero Guaraní: estado de conocimiento. Descripción del proyecto Guaraí a ser financiado por el Fondo Mundial para el Medio Ambiente. Un modelo conceptual y base de dato para el Sistema Acuífero Guaraní
Subject(s)
Shared Basins , Groundwater , International Water , Frontier WaterABSTRACT
Programa de la Reunión de Consulta. Síntesis del programa ISARM. Documentos de trabajo de la reunión. Inventario de Acuíferos transfronterizos europeos. El sistema Acuífero Guaraní: estado de conocimiento. Descripción del proyecto Guaraí a ser financiado por el Fondo Mundial para el Medio Ambiente. Un modelo conceptual y base de dato para el Sistema Acuífero Guaraní
