Mateus Pimentel de Matos

Performance of forage crops in wetlands used in the treatment of wastewater of coffee processing.

Duas gramineas forrageiras de inverno, azevem (Lolium multiflorum) e aveia preta (Avena strigosa Schreb), foram cultivadas em sistemas alagados construidos (SACs) utilizados no tratamento das aguas residuarias do processamento dos frutos do cafeeiro (ARC) com o objetivo de se avaliar seu desempenho agronomico. Essas forrageiras foram submetidas a diferentes cargas orgânicas (650 a 1.500 kg ha-1 d-1 de DQO), proporcionadas pela aplicacao dos efluentes de filtros anaerobios, utilizados no tratamento da ARC. Como tratamento testemunha, as mesmas especies vegetais foram cultivadas em solucao de Hoagland. A materia seca produzida pelas forrageiras ao longo dos 53 dias de monitoramento dos SACs variou de 7,4 a 14,0 e 0,5 a 2,7 t ha-1, e os rendimentos acumulados de proteina bruta variaram de 1.017 a 2.187 e 66,6 a 316,8 kg ha-1 para o azevem e a aveia, respectivamente. Os resultados permitiram concluir que, dentre as forrageiras estudadas, o azevem se mostrou mais adequado para ser cultivado em SACs utilizados no pos-tratamento da ARC efluente de filtros anaerobios, ja que apresentou maior rendimento de materia seca e proteina bruta e, portanto, melhor adaptacao ao sistema.

Extraction capacity of plants grown in constructed wetland systems used for treatment of dairy wastewater

The objective of this research was to evaluate the extraction capacity of two plant species when grown in constructed wetland systems (CWS) used for dairy wastewater (DW) treatment. The experimental units were formed by five CWS grown with Pennisetum purpureum schum grass and five CWS cultivated with grass tifton 85 (Cynodon spp.), with horizontal subsurface flow. The DW was applied at an average flow of 60 L d-1 and hydraulic residence time of 4.8 days, and subjected to organic loading rates (ORL) of 66, 130, 190, 320 and 570 kg ha-1 d-1 of BOD. The grass tifton 85 extracted more nitrogen and sodium, while the elephant grass extracted a larger amount of potassium from the DW, when grown under the evaluated organic loading rates (ORL). The concentration of phosphorus in aerial parts of plants and extraction capacity were similar in the two grasses, however, there is evidence of an increase in the extraction this nutrient, by the grass tifton 85, with the increase of the ORL applied in the CWS.

Influência da taxa de carga orgânica no desempenho de sistemas alagados construídos cultivados com forrageiras

The present paper was carried out to study the influence of organic loading rate (OLR) on the performance of subsurface flow constructed wetlands systems (CWs). Each CW was composed of a sealed tank of 0.40 x 0.73 x 3.00 m. The dairy industry wastewater was applied with flow rate of 60 L.d-1. In the control system, consisting of CW without vegetation, 130 kg.ha-1 d-1 of BOD was applied. In vegetated CWs (cultivated with elephant grass and tifton 85 bermudagrass), OLRs of 66, 130, 190, 320 and 570 kg.ha-1 d-1 of BOD were applied . The CW systems were efficient in the removal of BOD, COD, TSS, TS and nitrogen. OLRs between 250 and 400 kg.ha-1 d-1 BOD provide greater efficiencies in organic loading removal and above 400 kg.ha-1 d-1 in the solids removal from wastewater. The presence of the plants in the CWs showed to be important in the removal of N, K and Na of wastewater.

Difficulties and modifications in the use of available methods for hydraulic conductivity measurements in highly clogged horizontal subsurface flow constructed wetlands

Despite the fact that several authors consider the available measurement methods of hydraulic conductivity (ks) suitable for a good representation of the bed condition and clogging potential in horizontal subsurface flow constructed wetlands, others have questioned their adequacy. In this work, hydraulic conductivity measurements with conventional and modified methods were undertaken in two small full-scale units, one planted with cattail (Typha latifolia) and the other unplanted. Both units had already been operating for seven years and showed a high degree of clogging. It was observed that the use of the falling head method, with the introduction of the tubes during the test, provided results without a clear spatial trend. On the other hand, tests done on monitoring wells inserted during construction time showed, as expected, ks increasing with the horizontal distance from the inlet, but without reflecting actual field conditions. It was observed that, as the bed became more clogged, the use of the reported methods became more complex, suggesting the need of other methodologies. The use of planted fixed reactors (removable baskets installed in the bed) with evaluation of ks at constant head in the laboratory showed potential for the characterization of the hydrodynamic properties of the porous medium.

Clogging in horizontal subsurface flow constructed wetlands: influencing factors, research methods and remediation techniques

The treatment of wastewater in constructed wetlands (CW) has been increasingly applied throughout the world, as it is an efficient technique for the removal of pollutants and presents low construction and operational costs. However, a major operational problem of these systems is clogging of the porous medium. Clogging of CW has therefore attracted the attention in several studies, but there are several gaps in the understanding of this phenomenon, especially with regards to its genesis. In order to evaluate the contribution of the influencing factors and to facilitate remediation, it is important to have methods that favor characterization of the real conditions of CW. In this review, the objective was to gather information on the main factors interfering in the clogging process of horizontal subsurface flow constructed wetlands, the available and the new methods for characterizing the degree of obstruction of the porous medium and the techniques/strategies for unclogging these systems.