How can sewage plants go green

Polysaprobic zone was characterized by almost complete absence of algae except for blue-green alga Arthrospira Spirulina jenneri and green alga Euglena viridis. Bacteria and Protozoa were the most common groups in this zone. The preponderance of blue-green algae Cyanophyta was characteristic of alfa-mesosaprobic zone while diatoms Bacillariophyta and green algae Chlorophyta were dominant organisms in beta-mesosaprobic zone. Peridiniales Dinophyta and Charales Charophyta occurred in any quantity only in the oligosaprobic zone.

In the same zone, the bacterial count was low but there was a great variety of plants and animals including fish in considerable numbers. Biological wastewater treatment systems with micro algae have particularly gained importance in last 50 years and it is now widely accepted that algal wastewater treatment systems are as effective as conventional treatment systems. These spesific features have made algal wastewaters treatment systems an significant low-cost alternatives to complex expensive treatment systems particularly for purification of municipal wastewaters.

In addition, algae harvested from treatment ponds are widely used as nitrogen and phophorus suplement for agricultural purpose and can be subjected to fermentation in order to obtain energy from metane. Radiation is also an important type of pollution as some water contain naturally radioactive materials, and others become radioactive through contamination.

Many algae can take up and accumulate many radioactive minerals in their cells even from greater concentrations in the water [ 12 ]. MacKenthunemphasized that Spirogyra can accumulate radio-phosphorus by a factor Considering all these abilities of algae to purify the polluted waters of many types, it is worth to emphasize that algal technology in wastewater treatment systems are expected to get even more common in future years.

Wastewater treatment which is applied to improve or upgrade the quality of a wastewater involves physical, chemical and biological processes in primary, secondary or tertiary stages. Primary treatment removes materials that will either float or readily settle out by gravity.

It includes the physical processes of screening, commination, grit removal, and sedimentation. While the secondary treatment is usually accomplished by biological processes and removes the soluble organic matter and suspended solids left from primary treatment. Tertiary or advanced treatment is process for purification in which nitrates and phosphates, as well as fine particles are removed [ 27 ]. However initial cost as well as operating cost of wastewater treatment plant including primary, secondary or advanced stages is highly expensive [ 28 ].

It is well known that algae have an important role in self purification of organic pollution in natural waters [ 29 ]. Also, studies showed that algae may be used successfully for wastewater treatment as a result of their bioaccumulation abilities [ 39 ]. Aquatic communities representing various zones of pollution.

Survey of the saprobic zones and the corresponding communities[ 21 ]. There are a symbiotic relation among bacteria and algae in aquatic ecosystems.

Algae support to aerobic bacterial oxidation of organic matter producing oxygen via photosynthesis whilst released carbon dioxide and nutrients in aerobic oxidation use for growth of algal biomass.

Considering ammonium, carbon dioxide and orthophosphate as main nutrient sources, Oswald determined that oxygen release ratio is 1. Grobbelaar et al.

Algae using nitrogen and phosphorus in growth may remove to nutrients load of wastewater from a few hours to a few days [ 43 ]. In comparison to common treatment systems, oxidation ponds supporting growth of some species may be effective of nutrient removal Fig. Increasing dissolved oxygen concentration and pH cause for phosphorus sedimentation, ammonia and hydrogen sulphur removal.

High pH in algal ponds also leads to pathogen disinfection [ 44 ]. Removal efficiency of heavy metals by algae shows changes among species. In fact, studies showed that chrome by Oscillatoria , cadmium, copper and zinc by Chlorellavulgaris , lead by Chlamydomonas and molybdenum by Scenedesmus chlorelloides may remove successfully [ 45 , 46 , 47 , 48 , 49 ]. Although algae have adaptation ability to sub-lethal concentrations, accumulation of heavy metals in cells may be potentially toxic effects to the other circles of food web [ 50 ].

Algal-bacterial pond is water body which is designed to keep and improve of wastewater in a certain time. Stabilisation pond systems are assessed in different types: facultative, anaerobic, aeration and maturation ponds. Common pond type which utilizes from algae is facultative stabilisation ponds. Facultative ponds are designed for purposes such as decrease of waste retention time, achieve of effective treatment or algal culture Fig.

Algal photosynthesis and bacterial decomposition is principal mechanism of algal-bacterial ponds. The processes including oxidation, settling, sedimentation, adsorption, disinfection in the ponds are results of symbiotic relation between algae and bacteria populations [ 51 ]. Removal efficiency of organic nitrogen in treatment methods [ 44 ]. Facultative ponds usually 2. There are three main zones in such ponds; two upper zones with oxygen whilst anaerobic conditions prevail in bottom.

Algal photosynthesis and atmospheric diffusion are main oxygen source. Wastes are stabilized by aerobic bacteria in upper zone and by facultative bacteria in intermediate depths while degraded by anaerobic bacteria in bottom zone [ 53 ]. Zooplankton controls to excessive bacterial growth and algal blooms through grazing as well as contributing to carbon dioxide production for algal photosynthesis. Food web in a facultative pound is given in Figure 2. Acceptable effluent quality is the most important advantage of facultative ponds though low operation and maintenance costs.

However there are some disadvantages such as high land costs, odour problem in high waste loading, loss of nitrogen to atmosphere, limiting the nutrient reuse by phosphate sedimentation also limiting of irrigation potential by salinity increase during high evaporation period [ 54 ].

Although temperature largely affects retention time of wastewater, facultative ponds are widely used in different climate regimes. For example there are more than facultative ponds in Germany and France and in United States [ 53 ]. Municipal wastewater treatments with high rate algal ponds were first proposed by Oswald and Golouke and thereinafter were used in many parts of the world [ 55 , 56 ].

High rate algal pond is usually shallow cm and is equipped with mechanical aeration and mixing by means of paddle wheels.

High oxygen level resulting from photosynthesis and aeration allows to low retention times in these ponds. Removal rates of high rate algal ponds are almost similar to conventional treatment methods but may also be more efficient with lower retention time. Further, construction and energy costs are highly lower and land requirement is half the required for facultative ponds [ 57 ].

It is a well-known fact that only a small amount of nitrogen and phosphorus are removed in active sludge and bio filtration techniques, In addition active sludge and bio filtration techniques require expensive chemicals and complex systems. Cost of harvest in high rate algal ponds may be most important problem.

Thus sedimentation of algae with flocculating is aimed when the wheels are stopped for harvest. In addition growth of resistant algal species to sinking such as Chlorella, Euglena, Chlamydomonas and Oscillatoria is undesired algae in the ponds. Scenedesmus or Micractenium , non-preferred species due to their cell morphology for grazing, are dominant in well mixed ponds [ 40 ].

Harvested algae may use for industrial and agricultural use as well as effluent in aquaculture Fig. Advanced integrated wastewater pond systems are an adaptation of waste stabilisation ponds systems based on a series of four advanced ponds: A facultative pond; a high rate algal pond; an algal settling pond and finally a maturation pond for solar disinfection and pathogen abatement.

The first pond in series is a facultative pond with depth of 4 to 5 m containing a digester pit, which functions much like an anaerobic pond while surface zone remains aerobic.

Effluent of the facultative pond flows to the high rate algal pond for remove to dissolved organic matter and nutrients, then to settling pond with residence time of one or two days for sedimentation of algae and suspended solids. The last unit is maturation ponds where treated water is exposed to the sun and wind leading to natural oxygenation and solar disinfection, and thus an inactivation of pathogens [ 58 ].

Wastewater Treatment and Reclamation Plant in St. Helena, California, by US Department of Energy built of formed earth rather than of reinforced concrete in the early s Fig. The total pond area needed is much larger than that needed for a conventional plant, but ponds should still cost only one-third to one-half as much to build.

Another important advantage of the plant is the small amount of sludge they produced. For example, during nearly 3 decades of operation, St. Our waste has never looked so beautiful. Li, W-W. Figure of wastewater treatment plant courtesy of Annabel via Wikipedia. January 22, By: Jonathan Trinastic. Aa Aa Aa. The power of poop: revolutionizing wastewater treatment. The cost of reuse Feces, food scraps, fat, detergents Reclaiming our valuables Transforming this industry requires a perspective shift.

A call for support According to the authors, we are on the cusp of a revolution in how we deal with wastewater. References Li, W-W. Photo Credit Figure of wastewater treatment plant courtesy of Annabel via Wikipedia. Email your Friend. Submit Cancel. July 08, Goodbye and thank you! June 16, Desert dust increases harmful marine bacteria June 09, The greening of Vancouver June 03, Phosphorescent concrete could light the way home.

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Start with ruthe January 29, Greenland ice sheets losing ability to absorb m January 22, The power of poop: revolutionizing wastewater t January 15, When good intentions don't mix: designing polic January 08, Amazon resilience buoyed by diversity December 18, Beyond the headlines: clarifying the connection December 10, Where fuel goes, water cannot follow: impact of December 02, The many stories of climate change November 25, Solving the silicon swelling problem in batteries November 18, Making climate change local: how to motivate ci November 11, Short-term stability and long-term collapse: ex October 29, Equity or inertia: how emissions sharing philos October 15, Climate change in the classroom: visualizing gl October 07, Radiation or human intrusion: which factor is t September 30, Sequester in numbers: zooplankton migration tra The membranes in the system act as barriers between the biomass and the treated water.

Membrane manufacture and system testing The REMEB ceramic membranes were made at a ceramic tile company in Spain, opening a new line of business for the sector. Further demonstrating its potential, the technology was then replicated in Italy and Turkey at the pilot scale by using locally available waste resources such as coffee, hazelnuts, dolomite and shells.

The MBR was tested in a municipal wastewater treatment plant in Aledo, Murcia, a water-stressed municipality in south-eastern Spain.

Other applications for the technology include garden irrigation and street cleansing. Last update: 7 November Record number: Veuillez activer JavaScript.

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