Domestic Wastewater Depuration Using a Horizontal Subsurface Flow Constructed Wetland and Theoretical Surface Optimization: A Case Study under Dry Mediterranean Climate

Abstract

Abstract:The wastewater generated by isolated houses without access to public sewers can cause environmental problems, like the contamination of aquifers with nitrates and phosphates, as occurs in southeastern Spain. The effectiveness of a previously built horizontal subsurface flow constructed wetland (HF-CW) was studied over two years as a possible solution. This HF-CW measured 27 m 2 ; it was planted with Phragmites australis (Cav.) Trin. ex Steud ssp. altissima and the parameters studied were those required by European Union (EU) legislation and adopted by Spain. Average abatement efficiency rates, for the first and the second year of study, were: biochemical oxygen demand over five days (BOD 5 because its content in influent wastewater was very low and they appear mainly from influent NH 4 + -N, as a result of purification processes carried out in the HF-CW bed. The abatement rates make the system suitable to produce discharges into the environment in accordance with Spanish law. It is noteworthy that the HF-CW patch suffered an episode of bed drying during the summer of 2013, whereby the causes were related to system oversizing and high evapotranspiration in the area. As a consequence, the decrease in the abatement of water pollutants during the second year can be attributed to the creation of preferential water flow paths and short circuits through the constructed wetland (CW) bed. As a result of the oversizing of the CW, a theoretical resizing based on BOD 5 , TSS, TN or TP is proposed. The calculated values for the redesign were: 5.22 m 2 considering DBO 5 , 0.18 m 2 considering TSS, 10.14 m 2 considering TN and 23.83 m 2 considering TP. Considering the area where the HF-CW was located and in accordance with Spanish law for non-sensitive areas (no TN or TP requirements for wastewater discharge), BOD 5 is the most appropriate parameter for design; it is 5.2 times lower than the HF-CW initially built and without risk of bed drying.

Treatment of Municipal Wastewater Through Horizontal Flow Constructed Wetland

“…These physical mechanisms involved in sedimentation and filtration processes become more effective with an increase in hydraulic retention time (HRT). Substrate and macrophyte roots promote the sedimentation and filtration processes more effectively at reduced water speed and attained high percentage removal efficiency (> 91%), as shown in this study and those represented by different authors [11,24]. The results collected in this study showed that there was a complete reduction in TSS in most of the samples during the study period.…”

Wastewater Discharge through a Stream into a Mediterranean Ramsar Wetland: Evaluation and Proposal of a Nature-Based Treatment System

“…This pond would further enhance water remediation and might facilitate further benefits the Ramsar wetland. In this pond it would be suitable to use helophytic vegetation that plays an excellent role in Mediterranean wastewater purification [38]. The construction of two new ponds and the recovery of a temporary pond will contribute to increasing biodiversity in the study area.…”

Uses of Nanoclays and Adsorbents for Dye Recovery: A Textile Industry Review

“…Normal parameters exist for measuring contamination in general, which can be estimated with indicators such as biological oxygen demand at five days (BOD5) [49][50][51] and chemical oxygen demand (COD) [52][53][54][55], which indicate the amounts of oxygen needed to oxidize organic matter that is capable of being oxidized either biologically (bacteria and microorganisms) or chemically. There is one other parameter, the amount of total suspended solids (TSS) [56], which provides an idea of the amount of human matter in water.…”