Browsing by Author "Trein, Camila María"

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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.
Reduction of area and influence of the deposit layer in the first stage of a full-scale French system of vertical flow constructed wetlands in a tropical area
(2019) Trein, Camila María; García Zumalacarregui, Jorge Alejandro; De Andrade Moraes, Mirene Augusta; Sperling, Marcos Von
Utilization of the French system of vertical wetlands for treating raw sewage keeps increasing, but there is still limited consolidated information on their long term use in tropical countries. Under these conditions, there are indications that surface area requirements can decrease, whilst still keeping a satisfactory performance. However, variations in the operational mode and the role of the surface organic deposit layer under warm climatic conditions have not been fully investigated. The goal of this work was to evaluate the performance of a system comprised of only the first stage of the French system, with a further reduction of 1/3 of the area (utilization of only two units in parallel, instead of three) in terms of organic matter removal and nitrogen conversion, with one unit with a deposit layer accumulated over 9 years of operation, and the other unit without sludge layer, under Brazilian tropical conditions. The system was originally designed according to Cemagref/Irstea recommendations for the first-stage of the French system for the treatment of raw sewage generated by an equivalent population of 100 inhabitants. However, it was later on changed, and operated with only two units, using only 0.6 m2·pe−1. Feeding and resting periods were of 7 days each. In order to evaluate the influence of the sludge layer, the top sludge from one of the units was removed, and the performance of both units was compared by the Mann-Whitney test. The database comprises the wetland performance values in terms of dissolved oxygen (DO), redox potential (Eh), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), NH4+-N and NO3+-N, covering a monitoring period of 15 months. The effluent DO concentrations were significantly lower in the unit with top sludge, but still sufficiently high in both units. Although there were some variations between both units, effluent concentrations of the major pollutants were not significantly different in the units with and without sludge, and removal efficiencies based on mean values were considered good, given the reduced area of the system: BOD (80% and 79%), TSS (85% and 82%), TKN (60% and 63%) for the units with and without sludge, respectively. Under Brazilian climatic conditions, with the reduced area and employing longer feeding cycles (7 days), the sludge accumulation rate (less than 1 cm·year−1) was lower compared to the French mean values.