Olive Mill Wastewater Treatment by a Pilot‐Scale Subsurface Horizontal Flow (SSF‐h) Constructed Wetland

Abstract

Performances of a pilot-scale reed bed for the olive mill wastewater (OMW) treatment were investigated, by monitoring influent and effluent pH, total suspended solids (TSS), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), total phosphorus and polyphenols. In order to reduce the suspended matter concentration and to avoid clogging, OMW was pre-treated by adding lime putty, calcium hydroxide and hydraulic lime. The best results were obtained with 2 g/L of hydraulic lime. Pre-treated OMW was dosed in the reed bed at dilution ratios of 1/3 and 1/10 (v/v), pointing up that the latter only did not give rise to reed suffering and allowed to obtain good and durable removal efficiencies, above all for COD (74.1+/-17.6%) and polyphenols (83.4+/-17.8%). Recycling of the effluent was quite effective for the improvement of the wastewater quality, allowing a further removal of 26-70%, depending on the parameter taken into account. A post-dosage study, carried out by feeding the reed bed with the effluent of an activated sludge plant, pointed up a rapid decreasing of the outlet concentrations of the investigated parameters to values compatible with Italian regulations concerning wastewater discharge in surface water. Polyphenols were the exception, being their outlet concentration at the end of post-dosage study around 2 mg/L.

Treatment of Olive Mill Wastewater with Constructed Wetlands

“…A dilution of 1/10 with fresh water was applied in this study, as it was calculated as the minimum dilution necessary to ensure wastewater volumes for the viable operation of the CWs and to avoid detrimental effects on vegetation. The same dilution ratio was also used in a subsurface horizontal flow wetland operated with OMW after pretreatment of effluent with lime putty, calcium hydroxide and hydraulic lime [9]. Indeed, course of this study no visual signs of toxicity were observed for P. australis, an effect consistent with the excellent ability of this species to tolerate stressful conditions [16,17].…”

“…These effluents, similar to OMW, are characterized by high concentrations of organic matter and nutrients. To date, the use of CW as a potential means for OMW management has received little attention [9,10]. The restricted use of this practice in the Mediterranean region, where the major volume of global OMW production is produced, and its complex composition may be considered as probable reasons.…”

Constructed wetlands with light expanded clay aggregates for agricultural wastewater treatment

“…During this period it was noted that a pre-diluted OMW should be used in the assays instead of a raw concentrated one in order to reduce the phytotoxicity of the phenolic compounds and major clogging problems caused by high concentrations of suspended solids. In fact, in a real application, the OMW can be dosed in a CW at very little hydraulic loading rates and after dilution by taking advantage of the facts that OMW are produced in a short period of the year and there is a long elapsing time between two subsequent oil campaigns (Del Bubba et al, 2004).…”

“…In recent years, the use of constructed wetlands (CWs) for the treatment of agricultural wastewaters, including those produced by food-processing industries and by livestock farms, has been gaining popularity due to their relatively low construction costs and maintenance requirements (Cronk, 1996;Knight et al, 2000;Del Bubba et al, 2004;Carty et al, 2008;Harrington and McInnes, 2009;Yalcuk et al, 2010;Herouvim et al, 2011;Yalcuk, 2011;Harrington et al, 2012;Kapellakis et al, 2012;Justino et al, 2012). Their use as buffer zones to provide effective protection of water bodies from agricultural runoff events, namely for the containment of associated pesticide contamination hazards, has also been studied and applied (Gregoire et al, 2009;Warsaw et al, 2012;Matamoros et al, 2012b).…”

The effects of flow regime and temperature on the wastewater purification efficiency of a pilot hybrid constructed wetland

“…Several studies have been carried out in VSSF filters of tidal flow for the treatment of municipal wastewater [12][13][14] and piggery wastewater [11,15]. Also, in downflow regime VSSF filters of 1-stage [16][17][18], 2-stage [19], and 3-stage [20], HSSF filters [21], and hybrid (combined from VSSF and HSSF filters) CWs [22][23][24] treating domestic and farm effluents, recirculation has been successfully used. Likewise, recirculation has significantly enhanced the purification of landfill leachates [25,26].…”