Browsing by Author "Von Sperling, Marcos"

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Dynamics of the behaviour of a vertical wetland (french system) operating in warm-climate conditions, evaluated by means of variables continuously measured in situ
(2020) De Andrade Moraes, Mirene Augusta; García Zumalacarregui, Jorge Alejandro; Trein, Camila María; Von Sperling, Marcos
The sewage treatment system in this study was operated with only the first stage of a French system of vertical wetlands, composed of two units in parallel and running with an extended feeding cycle (7 days). This research sought to evaluate and relate continuous variables measured in situ (dissolved oxygen (DO), pH and redox potential) throughout the feeding cycle, with measurements at distinct heights along the filter vertical profile. Additionally, the influence of the surface organic sludge deposit was investigated. A close link between the hydraulic behaviour and the effluent quality was verified, with both being related to the batch volume and the instantaneous hydraulic loading rate. The drop in DO as the feed days progressed could be related to the loss of hydraulic conductivity. A thicker sludge layer decreased the aeration capacity of the filter. The effluent was observed to be aerated when percolating through the medium. DO and pH data suggested that nitrification varied along the filter depth, the batch duration and the feed cycle. The monitored parameters may be indicative of the behaviour of other parameters.
Performance of a French system of vertical flow wetlands (first stage) operating with an extended feeding cycle
(2019) Trein, Camila María; García Zumalacarregui, Jorge Alejandro; De andrade Moraes, Mirene Augusta; Von Sperling, Marcos
The aim of this work was to evaluate the treatment performance in the first stage of a vertical flow constructed wetland – French system (VCW – FS) during an extended feeding period (seven days), in two parallel units, for a population equivalent around 100 inhabitants (total of 0.6 m²·p·e.−1), under Brazilian tropical climatic conditions. One of the units had a greater surface sludge deposit layer, accumulated over nine years of operation, while the other unit had its sludge removed prior to the experiments. Four intensive monitoring campaigns covering all days of the feeding cycle were undertaken and the results were compared with those obtained from the conventional monitoring. The results indicated that, as the days of the feeding cycle progressed, dissolved oxygen concentrations decreased, but was still kept at sufficiently high values for the removal of organic matter. Therefore, COD removal, although not high, remained acceptable for compliance with local discharge standards during all the period. The NH4+-N removal efficiency and NO3−-N production were larger at the beginning of the feeding cycle, as a result of the more well-established aerobic conditions, with the nitrification rate decreasing from the third day of feeding. The sludge deposit seemed to hinder the liquid percolation, especially at the end of the feeding cycle, thus affecting oxygen transfer. Due to the variability of the results along the feeding cycle, if sampling is to be done once-a-week, it is important to identify the sampling day that best represents the system's performance.
Performance of the first stage of the French system of vertical flow constructed wetlands with only two units in parallel: Influence of pulse time and instantaneous hydraulic loading rate
(2018) García Zumalacarregui, Jorge Alejandro; Von Sperling, Marcos
The technology of vertical flow constructed wetlands - French system for treating raw wastewater depends on several hydraulic factors, one of them being the duration of the pulse feeding and the resulting instantaneous hydraulic loading rate. This paper analyses two scenarios in the same system, the first of a faster feeding by pump and the second of a slower feeding by siphon, both with instantaneous hydraulic loading rate values lower than the literature recommendations. The system treated raw wastewater from a population equivalent of 100 p.e. in Brazil, and was comprised by only the first stage and two units in parallel. The shorter duration of feeding time and higher instantaneous hydraulic loading rate were associated with significantly higher chemical oxygen demand and total Kjeldahl nitrogen removal efficiencies, but with no significant differences in terms of biochemical oxygen demand (BOD) and suspended solids (SS). Oxygen concentrations and redox potential in the effluent were evaluated, together with the effluent flow rate profiles. The removal efficiencies were associated with the accumulation of solids in the upper part of the filter resulting from seven years of operation and to the operating hydraulic conditions, which are important elements in the performance of the system. © IWA Publishing 2018.
Potential use of tifton 85 cultivated in VFCW for animal feed
(2020) Coelho Lopes, Bruna; García Zumalacarregui, Jorge Alejandro; Matos, Mateus; Matos, Antonio; Von Sperling, Marcos
The objective of this study was to evaluate the nutritional value of Tifton 85 grass (Cynodon dactylon (L) Pers) cultivated in a vertical flow constructed wetland (VFCW) system treating raw sewage. The VFCW operated according to the French system, but with only the first stage and two units in parallel, using a small footprint of 0.6 m2 per inhabitant. Wastewater feeding and resting periods were of seven days each. To evaluate the yield and nutritional value of the Tifton 85 cultivated, samples were collected after 30, 45, 60, 75 and 90 days of growth. They showed yields of 16, 28, 36, 36 and 38 t·ha1 of dry matter (DM), respectively. The crude protein content decreased sharply during 60 days, however, with values of 29, 23, 15, 15 and 15% DM for the same days, respectively. The results indicate that Tifton 85 could be used for hay production and, to obtain better yield and quality, when used to treat raw wastewater the forage should be cut after between 45 and 60 days of growth.