Urban wastewater causes rapid eutrophication of natural waters and requires treatment before discharge. This is expensive and produces huge quantities of sludge. In the European Community, it will no longer be lawful  to dispose of this sludge as landfill after 2005 (European Directive91/271/CEEof May21, 1991). Wastewater treatment by theChrysanthemum cinerariaefolium plants in horizontal flow was investigated using the nutrient film technique (NFT), a widely used hydroponic system in the commercial greenhouse industry. After a 48 h plant treatment, the purification efficiency was 95%, 91%, and 99% with respect to suspendedsolids (SS), biochemical oxygen demand (BOD5), and chemical oxygen demand (COD), and the elimination of nutrients (total nitrogen and total phosphorus) varied between 40% and 80%.  SS and thus indirectly BOD5 and COD were removed by filtration and adsorption; the solids trapped in the root systems were then decomposed and mineralized. The system with 25 plants purified 30 L of wastewater in 48 h. One-hundred people communities wastewater could be treated witha 6 m2 area of production. Pyrethrin contents and chlorophyll a fluorescence of plants grown on raw urban waters were not significantly different from those grown on a standard nutrient solution.

Introduction

Direct ive 91 / 271 of the Europea n Union concer ning urba n wastewater treat ment requires member states to comply with discharge standards for tert iary pu rification (nitrogen and ph osph orus re moval) to be applied first in sensitive areas to eutro phication (1). These treat ments are expensive and produ ce huge qua ntities of sludge that it will no longer be possible to dispose as landfill after 2005 (Europea n Direct ive 91 / 271 / CEE of May 21, 1991). In add ition, the collection and treat ment of wastewater in low population density areas  is

* Corres ponding author ph one: 33 4 71 45 57 55; fax: 33 4 71  75 57 59; e- mail:  ad nane.hitmi@u-cler mont1.fr.

†  Universite´  d’Auvergne.

‡  Universite´  d’Avignon.

problematic. Dece ntralized sewage treat ment is usually inevita ble for eco nomic reasons, bu t the curre ntly available tec hn ologies for the treat ment of wastewater from single houses, dwellings, and small comm unities re mains un sat- isfactory in many aspects. The incre ase in the population of rural areas and thu s the incre ase in the produ ction of wastewater and the significant use of agricultural fertilizers lea ds to  the eutro phication of aq uatic ecosystems (2).

Beca use conventional sewage treat ment plants only partially re move nitrogen and ph osph orus from wastewater, there is need to develop low-cost energy-efficie nt wastewater treat ment systems suited to rural areas. Rece ntly, consider- able atte ntion has been directe d toward wastewater treat ment processes using constr ucte d wetlands consisting of bed filters planted with emergent plants, beca use of the low cost and ease of operat ion (3). The use of constr ucte d wetlands/ ree d bed treat ment systems has grad ually developed over the past 20 years (3-5). As com pared with conventional wastewater treat ment systems, they are relatively inexpensive to constr uct and maintain, while providing effective and reliable waste- water treat ment (6).

Macrophytes, ranging from du ckweeds (7) through water hyacinth (8), catta ils, ree ds, and sedges (9), are generally planted in wetlands. Studies condu cte d on the re moval of tota l ph osph orus (10-12) and tota l nitrogen (10-13) showed a very wide range of treat ment effective ness. These plants enh ance biopersity, bu t they have no  uses  for rural comm unities other than pu rification. Jewell has combined the anaerobic treat ment of primary sewage with a specialized hydroponic (water as a growth medium) seco ndary or tert iary treat ment system that yields biomass (14). Accordingly, we investigated the possibility of intro du cing valuable com- mercial species such as Chrysanthem u m cinerariaefoliu m into the treat ment system. A raw efflue nt treat ment has bee n developed using a terrestr ial species (Chrysanthem u m cin- erariaefoliu m ) using the nu trient film tec hniqu e (NFT) developed initially by Coo per (15). We review some of the studies carried out to evaluate and compare the effective ness of this system.