Taking wind into account in the design of waste stabilisation ponds.

Up to now, most investigations on the dependency of the fluid flow patterns and performance of waste stabilisation ponds (WSPs) on wind speed and direction and pond layout have been performed using 2D and 3D CFD steady state isothermal models. 3D non steady state models integrating thermal processes and boundary conditions taking into account the full influence of meteorological factors are likely to provide more realistic predictions of WSP performance. Such modelling was undertaken for 4 pond layouts, 2 without baffles and 2 with baffles.

Fluid flow pattern and water residence time in waste stabilisation ponds.

As treatment processes are kinetic-dependent, a consistent description of water residence times is essential to the prediction of waste stabilization ponds performance. A physically-based 3D transient CFD model simulating the water velocity, temperature and concentration fields as a function of all influent meteorological factors--wind speed and direction, solar radiation, air temperature and relative humidity--was used to identify the relationships between the meteorological conditions and the hydrodynamic patterns and water residence times distributions in a polishing pond. The required meteorological data were recorded on site and water temperatures recorded at 10 sampling sites for 141 days.

Positive gadolinium anomalies in wastewater treatment plant effluents and aquatic environment in the Hérault watershed (South France).

Anthropogenic gadolinium (Gd), used as a contrast agent in magnetic resonance imaging, may enter rivers and groundwaters with the effluents of wastewater treatment plant (WWTP). Such contaminations, which are mainly found in densely populated areas with highly developed medical systems, induce positive gadolinium anomalies in waters. This study reports on the occurrence of positive Gd anomaly in wastewaters, surface and groundwaters in a slightly populated Mediterranean watershed.

Organotins in a medium-size Mediterranean basin (the Herault River).

This study reports the first assessment of organotin pollution in the Hérault watershed, a medium size Mediterranean basin. Organotin compounds were analyzed in surface waters, wells supplying drinking water and sewage treatment plants (STPs). In surface and ground waters, a background contamination by total organotin compounds has been identified in the range of 0.

Water reuse for urban landscape irrigation: aspersion and health related regulations.

The Mediterranean seaside resort of Le Grau du Roi includes 40 hectares of landscaped areas spray irrigated with river water supplied through a separate network. Wastewater collected from several municipalities is treated in an activated sludge wastewater treatment plant (WWTP) and polished in waste stabilization ponds (WSPs). Planned substitution of treated wastewater for river water is hindered by spray irrigation prohibition within a 100 m distance from houses and recreational areas.

Wastewater infiltration percolation for water reuse and receiving body protection: thirteen years' experience in Spain.

Infiltration percolation (IP) is an extensive technology to treat primary or secondary effluents of small and middle size communities before reuse or disposal to sensitive receiving bodies. Thirteen years of implementation of IP in Spain has highlighted the necessity to abide by defined design and construction rules and operation conditions in order to achieve consistently the treatment objectives and guarantee a long lasting treatment capacity. From this experience, high care should be taken of (i) the characteristics of the sand constituting the filter, (ii) the drainage conditions, (iii) the influent spreading over the infiltration surface and (iv) the risks related to recurrent overloading.

Low technology systems for wastewater treatment: perspectives.

Low technology systems for the treatment of wastewater are sometimes presented as remnants of the past, nowadays supposedly only meant to serve developing countries and remote rural areas. However, considering their advantages and disadvantages together with enhanced treatment requirements and recent research and technological developments, the future of these systems still appears promising. Successful applications of low technology systems require that more care is taken of their design and operation than often observed.

Consequences of treated water recycling as regards pharmaceuticals and drugs in surface and ground waters of a medium-sized Mediterranean catchment.

In Mediterranean regions where the population is rapidly growing, the risk of water resource contamination by wastewater is likely to increase. This is the case of the Hérault watershed (south of France), where the presence of treated wastewater in surface and ground waters has been shown in a previous study. To assess the consequence of these wastewater contaminations as regards pharmaceuticals and other organic compounds, 16 common pharmaceuticals (amitryptilin, acetylsalicylic acid, carbamazepine, clenbuterol, diazepam, diclofenac, doxepin, gemfibrozil, ibuprofen, imipramine, ketoprofen, naproxen, nordiazepam, paracetamol, salbutamol, and terbutalin) as well as wastewater related pollutants (caffeine, gadolinium anomaly, and boron) were analyzed in wells pumped for potable water supply and in two wastewater treatment plant (WWTP) effluents.

Microphyte and macrophyte-based lagooning in tropical regions.

A 720 m2 plant made of 8 ponds in series, set in Yaounde (Cameroon), was successively operated as a macrophyte-based system (type M) from November 1997 to October 98, a microphyte-based system (type m) from October 1999 to September 2000 and a combination of macrophyte and microphyte ponds (type M + m) from May to July 2001. Average applied loads varied over the years; from 420 kg. BOD5 ha(-1)d(-1) on the year 1997/98, the loads reached 510 kg BOD5 ha(-1)d(-1) in 1999/2000 and 500 in 2001.

Mosquito development and biological control in a macrophyte-based wastewater treatment plant.

A one-year study of the proliferation of mosquito in a Pistia stratiotes-based waste stabilization ponds in Cameroon revealed that Mansonia and Culex were the main breeding genera with about 55% and 42% of the total imagoes respectively. Though the ponds represent a favorable breeding ground for mosquitoes, only 0.02% of captured imagoes was Anopheles gambiae, suggesting that this wastewater treatment plant does not significantly contribute to the development of the malaria vector in the area.

Twenty years' monitoring of Mèze stabilisation ponds: part II--Removal of faecal indicators.

The WSP system serving Mèze and Poussan (French Mediterranean coast) was constructed in 1980 and enlarged and upgraded from 1994 to 1998. Water quality along the waste stabilisation pond to (WSP) system has been monitored over the years, thus allowing us to assess the influence of enlargement and upgrading works. A significant enhancement of the average microbiological quality of the effluent was observed, with respective E.

Twenty years' monitoring of Mèze stabilisation ponds: part I--Removal of organic matter and nutrients.

The Mèze stabilisation pond system has been monitored over more than 20 years. Despite the enlargement of the plant, the organic load doubled between the early 1980s and recent years, the removal of organic matter and nutrients has been maintained at the same level for COD and increased for BOD5, N and P. Combining anaerobic, step-fed aerated and maturation ponds and multiplying the number of cells resulted in a significant improvement in the performances of the plant.

Setting up microbiological water reuse guidelines for the Mediterranean.

Water reuse is a widespread practice in most Mediterranean countries. Some countries have no wastewater treatment facilities and direct reuse of raw wastewater is occurring while others have a well-established national reuse policy. Water reuse microbiological standards, when existing, significantly differ from one country to another.

Oxidation processes and clogging in intermittent unsaturated infiltration.

Intermittent infiltration of wastewater through a non saturated sand bed is an extensive treatment process aimed at eliminating organic pollution, oxidizing ammonia and removing pathogens. A 1D numerical model, IPOX, has been worked out to simulate the transfer and oxidation of dissolved organic matter and nitrogen in unsaturated sand beds. IPOX was calibrated after real scale tests performed in Spain and Burkina Faso.

Mixing and its impact on faecal coliform removal in a stabilisation pond.

Faecal coliform removal in stabilisation ponds is highly dependent on shortest water retention times. Tracer tests have been performed in a 3,300 m2 and 1.0 m deep pond, located in Southern France, to measure the retention times and bring light on the main influencing factors and mechanisms.

Design of a climate-dependent water reuse project.

Reclaimed water storage is imperative in water reuse management. Climate is a primary factor controlling reclaimed water storage design by its significant influence on irrigation water needs as well as on stored water quality. This study presents a modelling approach that has been applied to assist the design of a climate-dependent water reuse project on an Atlantic island.

Modelling of a recirculating granular medium filter's processes.

The effluents of French small farm factories will soon be submitted to regulation. Only a few treatment techniques are available to deal with these kind of effluent (high concentration and small daily volumes). To allow the treatment, in the particular economic context of small food processing industries, Cemagref is trying to adapt a treatment based on attached growth cultures on fine media, a system known to be easy to operate and relatively inexpensive.

Use of recycling through medium size granular filters to treat small food processing industry effluents.

Currently there are no suitable wastewater treatment systems for effluents from small food processing industries (dairy, cheese, wine production). Such raw sewages are characterized by high organic matter concentrations (about 10 g COD L-1) and relatively low daily volumes (about 2 m3). An adaptation of attached-growth cultures on fine media processes, known to be easy and inexpensive to use, could fit both the technical and economical context of those industries.

Non-steady-state modelling of faecal coliform removal in deep tertiary lagoons.

In Noirmoutier, a French island off the Atlantic coast, secondary effluents flow into a series of four lagoons, 1.4-2.8 m deep, and are reused for agricultural irrigation.

[Pollution of the groundwater in the city of Niamey, Niger].

We conducted a study on chemical and bacteriological groundwater pollution in Niamey, a Sahelian city of some 700,000 inhabitants. A total of 22 wells and 24 bore-holes were selected on a geological and socio-economic basis. The superficial aquifers, located on each bank of the River Niger and connected to the wells, presented high levels of oxidizable nitrogen and bacteriological pollution (coliform and faecal Streptococcus) which make the water unfit for human consumption.

Technical-economic modelling of integrated water management: wastewater reuse in a French island.

An integrated technical-economic model is used to address water management issues in the French island of Noirmoutier. The model simulates potable water production and supply, potable and non potable water demand and consumption, wastewater collection, treatment and disposal, water storage, transportation and reuse. A variety of water management scenarios is assessed through technical, economic and environmental evaluation.

Role of water reuse for enhancing integrated water management in Europe and Mediterranean countries.

Recycling water is an important aspect of water resource and environment management policies, ensuring reliable alternative water resources, reducing environmental pollution and achieving a more sustainable form of development. This paper focuses on wastewater reuse as a strategy for integrated water management. Key economic, financial, regulatory, social and technical factors that help to make water reuse projects successful are reviewed.

Reuse of reclaimed wastewater for golf course irrigation in Tunisia.

In Tunisia, golf courses are irrigated with secondary treated effluent stored in landscape impoundments. The impact of the conveyance and storage steps on the physical-chemical and biological quality of irrigation water was evaluated on three golf courses over two years. It was found that the water quality varies all along the water route, from the wastewater treatment plant up to the irrigation site: nutrient and bacteria contents decreased along the route in the three cases.