Autotrophic hydrogenotrophic denitrification is a treatment method performed by culture of proper microorganisms using the nitrate anion as the final electron receptor under anoxic conditions.

It is a promising method for nitrate removal, where pure hydrogen and carbon dioxide are used as the electron donor and carbon source, respectively. Hydrogen is produced in situ using an electrolysis cell powered by a photovoltaic cell.

Among the most common pollutants in the Greek territory are ammonia, iron and manganese. The presence of ammonia in aqueous reservoirs is usually associated with the simultaneous presence of significant amounts of iron and manganese at concentrations above the permissible levels. It is therefore essential to remove these three elements from drinking water. At the Environmental Systems Laboratory, the simultaneous removal of ammonia, iron and manganese was studied using a pilot-scale trickling – filter with dual layer support material of low cost, in which are attached microorganisms oxidizing all three pollutants.

Silic gravel trickling-filter is a heterogeneous biological process that aims to remove organic matter from wastewater by oxidation and synthesis processes. It is also used for nitrification, that is, the conversion of ammonia contained in liquid waste and potable water into nitrates. Unlike the homogeneous processes, in the heterogeneous, the microorganisms remain in the biological filters (silic gravel trickling - filters) for a long time, as they are attached at the support material and act as microorganism inoculums. In this way biological oxidation of pollutants can occur in smaller volumes with much better results and of course at lower costs.

The removal of organic matter and pigments contained in industrial wastewaters is also among the subjects of ESLaboratory.

Applying electrochemical methods, the optimum conditions, such as processing time, initial organic charge, electrode material, and current density, are investigated to remove both organic matter and pigments from dairy, edible olive and paper waste, in order to be safely disposed in the environment.

The simulation of the process is developed using mathematical models. The results of this research work are also applied in industry by constructing and successfully apply a pilot-scale electrocoagulation unit.

Composting is a natural process that converts organic matter into a rich substance called compost and used as a soil conditioner. Composting is a very immediate and important way of recycling. It has been estimated that 35% of household waste can be composted.

Bacteria, fungi and other endogenous microorganisms are the 'workers' of composting. During composting, they produce carbon dioxide (CO2), heat and water as they degrade the organic materials of the wastes. The end product is COMPOST (rich, dark, sour and odorless) which is considered to be an excellent soil conditioner.

Agroindustrial wastes contain large amount of organic and inorganic compounds. For this reason, urban wastewater treatment plants do not accept these wastes untreated and a pre-treatment step is needed.  However, the most common practice is to uncontrollably dump them into the environment causing huge pollution problems.

The wastes of most of the agro-industrial plants have a discontinuous production and their runoff rate can change significantly. Also important are seasonal variations in their production depending on the availability of raw material that the plant processes each time. Until recently, the daily practice of managing most agricultural waste was to discharge it without treatment to the local water and soil recipients. However, the application of biological treatment significantly reduces their organic matter and makes them safe for disposal in the natural environment.

The culture of photosynthetic microorganisms is a process of biotransformation of nutrients into high-added value products.

The aim of the experiments in the ESLaboratory is to recover nutrients from waste streams using mixotrophic cultivation of microalgae in laboratory-scale photoreactors.

The purpose of this research is also to fully characterize the produced biomass of microalgae for its further exploitation in a variety of applications.

ESLaboratory is also focused on the recovery of ammonium nitrogen from dairy waste and landfill leachate applying adsorption technique, while natural zeolite is examined as an adsorbent.

The experiments are related both to the study of the adsorption capacity of the zeolite to the initial waste concentration and temperature to intermittent reactors, and to the finding of the ideal zeolite granulometry for maximum ammonium nitrogen recovery.

The contribution of nitrogen from the use of saturated zeolite (in terms of ammonium nitrogen) in the growth of wheat plants in pots, is also examined.

Constructed Wetlands are a natural system for the treatment of municipal and agricultural wastewaters and sludge. They are based on the use of plants and the supply of waste to such systems takes place above or below the soil surface.

The main advantages of Constructed Wetlands are the low cost of construction and operation compared to a conventional installation. They operate without external energy supply since the energy required comes from renewable sources used by plants (sun, water and sludge nutrients) and have high stability in decontamination performance without undesirable odors.

It can also be expanded at any time and visually in harmony with the natural landscape.