Abstract
The confined dairy cattle system employs the most modern production techniques with respect to the genetic standards of the herds. The success found in these systems promoted an increase in the number of confined animals and, consequently, an increase in the produced volume of waste, causing the waste from dairy cattle farming to be one of the largest problems in intensive management systems. This effluent has high amount of phosphorus and nitrogen, and the accumulation of these nutrients in surface waters can cause eutrophication of water courses deteriorating their quality. This study is aimed to evaluate the efficiency of a constructed wetland system, cultivated with vetiver grass (Vetiveria zizanioides) in the removal of important environmental pollutants nitrogen (N) and phosphorus (P) from dairy cattle farming wastewater. The effluent received pre-treatment and before passing through the constructed wetland system which was built in a trapezoidal shape. The wastewater from dairy cattle farming, at the inlet and outlet of the constructed wetland system, was biweekly analyzed for different forms of N (ammonia, total Kjeldahl N, nitrate and nitrite) and P. The constructed wetland system proposed cultivated with vetiver grass showed good removal pollutants with greater mean efficiency in the removal of nitrite (43.6%), the total Kjeldahl nitrogen (32.0%) and ammonia (31.0%). Vetiver grass cultivation showed good adaptation to the constructed wetland system, with satisfactory development and no visual symptoms of nutrients deficiency. Key words: Cultivated beds, water resources, wastes, reuse, biological treatment.
Highlights
Agricultural activity plays an important role in the national economy, besides being one of the first economic activities to be developed in the country
The treatment system of wastewater from dairy cattle farming (WDCF) comprised a pilot treatment unit consisting of: compost box, sedimentation tank, crushed stone filter, organic filter and constructed wetland system (CWS) with horizontal subsurface flow which was sized according to methodology presented by Marques (1999)
The concentrations of all parameters analyzed in the effluent, at the CWS outlet, were lower than those at the inlet, demonstrating that there was a reduction of these parameters in the system
Summary
Agricultural activity plays an important role in the national economy, besides being one of the first economic activities to be developed in the country. With the increase in food demand, agriculture has used more areas to intensify production. In Brazilian agriculture, dairy farming has stood out and milk has gained space in the market, being among the most important products of this activity. The confined dairy cattle system employs the most modern production techniques regarding the genetic standards of the herds. The success found in these production systems promoted an increase in the number of confined animals and, an increase in the produced volume of waste, making it one of the largest problems in intensive management systems and a challenge for farmers and specialists, because it involves technical, sanitary and economic aspects.
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