The presence of inorganic compounds containing oxidable nitrogen within groundwater sources at various,high concentration levels, especially in the case of NH+4 (NH+4 ≤ 8 mg/l), is asking for the replacement of classical oxidation technology using “break point” chlorination, due to non-conformities generated by high consumptions of chlorogenic agents (tens mg Cl2/l) upon the quality of treated water (acid pH, high ratio of residual bound chlorine, trihalomethans above the maximum admissible concentration). Biochemical oxidation using a bio-filter system in specific operating conditions (media type, temperature, oxygen demand, inorganic carbon and phosphorus sources, biological contact time, etc.) is representing a feasible technological alternative. Taking into account that carbon source used within the biochemical process is inorganic, the dissolved natural organic matters (NOM- humic matters) can react with the chlorine used in the final stage of biological effluent treatment. In the conditions of advanced removal of NH+ 4, oxidation to NO- 3, the chlorine dosages needed for effluent‟s finishing, disinfection are reduced. Experimental tests have as objectives to set up the chlorine dosage (Cl2 = 0,5 † 0,8 mg/l) that assures the disinfection of effluents resulted from biological nitrification step and a minimum ratio of residual bound chlorine, as well as the assessment of trihalomethanes formation potential in case of dissolved organic load, DOC ≤ 1,8 mg C/l (weight rations Cl2 / DOC = 1 † 8).

The temperature influence upon the nitrification rate was studied using a continuous flow pilot installation, which comprises a biological aerated filter with ascendant inflow circulation. Used filter media was expanded clay, 2-5 mm granulometric fraction. The biofilter was fed with raw low - depth groundwater enriched with NH+ 4. Inorganic nitrogen forms (NH4+, NO2-, NO3-) concentrations were measured both within the inflow and outflow of aerated biological filter, at stationary operation regimes in correspondence with various applied NH+ 4 loading. Values of NH4+removal rates were situated within the 515-1337 g NH4+-N/m3*day domain for temperature increase from 11 to 25.2 C degree. The coefficients of reaction rate vs. reaction temperature equation were also determined.

In this review the synthesis, functionalization and some applications of magnetite nanoparticles (MNPs) were highlighted. It is our intention to highlight the correlations between the synthesis routes, related synthesis parameters, functionaliztion strategies and the properties expected for the materials containing MNPs. The uses of MNPs are strongly influenced by the properties of the materials. Therefore this review is trying to discuss the applications of the magnetite and magnetite based nanomaterials by taking into account all the factors that can influence the properties of the final materials and consequently their potential applications.

Chlorine is a common disinfection agent used in the natural water supplies treatment in order to ensure the microbiological safety of drinking water. At the same time, chlorine is used as oxidant agent for removal of oxidable pollutants from groundwater, especially for ammonium ions. The high doses of chlorine imposed by ammonium break point chlorination process (Cl2:NH4+ = 8 ÷15:1) generate also chlorinated by-products such as trihalomethans (THMs) and haloacetic acids (HAAs) with potential carcinogenic effects. The brominated species were suspected to be much stronger carcinogens and mutagens than their chloride – containing analogues. The reaction between chlorine and natural organic matter (NOM), which contain substantial amount of humic substances (HS) and also the THMs concentration level, are affected by several factors as: pH, temperature, dissolved organic carbon (DOC), bromide concentrations, chlorine dose, contact time. The present paper has as main objective the evaluation of halogenation effect on THMs formation and upon evolution of some indicators of NOM quality / reactivity (A254, SUVA) for three groundwater sources with different pollution degrees (DOC = 2 ÷ 4,5 mgC/l, NH4+ = 1,6 ÷ 10mg/l, Br - = 0,1 – 1,1 mg/l).

Mine water treatment can be seen as challenging, but also a long-term task. In addition to better known acidity correction and heavy metals and metalloids removal, the mine water treatment approaches are slowly shifting to advanced methods, targeting the elimination of the salinity. Some methods for the sulfate and calcium removal are advancing to industrial implementation (e.g. ettringite precipitation, membrane separation and combinations of these methods), but the cost is high and the cost to benefit result may be controversial. On other hand, the seeded crystallization of gypsum can lower the sulfate and calcium concentration after conventional treatment by liming. Despite that this technique is limited by the gypsum solubility, it is bringing considerable benefits as a second treatment stage after the conventional liming, by safely lowering the sulfate concentration from 2000...4000 mg/L to about 1500 mg/L, together with the equivalent calcium quantity. Due to the fact that this method is using recycled gypsum produced within the process, it can be seen as a sustainable practice. This is illustrated by a case study for a mine water source with an initial sulfate content of about 5000 mg/L.

Mine water or rock drainage is a source of pollution for Romanian as well as for mining sites all around the world. Rock drainage is generated as a result of the weathering of the sulphidic minerals from which metal ions are leached. The metal ions are the main polluting species existing in the mine water, but may also be seen as a resource that is wasted. However, the recovery is seldom applied, as it is not feasible due to complex chemical matrix. Some types of mine water are more appropriate for the resource recovery, the best known case being copper reach streams. Here we show some attractive results suggesting that the recovery of aluminium, but also of manganese would be feasible practices for particular mine water categories and for distinct utilizations: mine water treatment and high purity resource for metallurgy, respectively.

The composition of groundwater is of interest for drinking water service providers due to its implications upon the potabilisation treatment flow. The paper is presenting two case studies from Romania, each groundwater sources containing ammonium and organic load reactive to chlorine. Oxidation tests for NH4+ were performed using chlorine and sodium hypochlorite on water samples with the following characteristics: NH4+ ≤ 4.4 mg/L and DOC < 1 mg/L. Oxidation tests with chlorine at the breakpoint showed that a weight ratios of Cl2 : N-NH4+≥ 10 : 1 and reaction time of 40 min are needed in order to assure a remanent concentration of NH4+ below the admissible value of 0.5 mg/L, residual chlorine concentrations being in the range of 12-20 mg/L, and THM concentration after 24 h in the range of 102-277 µg/L. Oxidation tests with NaOCl showed that even at high doses of active chlorine (30 mg/L) and long reaction time of 24h, remanent ammonium concentration is higher than the admissible value of 0.5 mg/L, residual chlorine concentration being of mg/L order. In this case, selection of an alternative raw water source or the replacement of classical oxidation technology using chlorine by biological nitrification is needed.

Chlorinated ethenes such as 1,2-dichloroethylene (1,2DCE), trichloroethylene (TCE), tetrachloroethylene (PCE) were identified in some groundwater sources used for potable purpose. Contamination of groundwater can occur from many sources, the most important of which being leachates from waste disposal sites. Analysis of contaminated groundwater has shown high concentration level of halogenated volatile organics (1,2DCE = 14-18 mg/L, TCE = 80-130 mg/L, PCE = 198-258 µg/L), over the current limits imposed by enforced legislation (L 458(r1)/2011: MACTCE + PCE = 10 µg/L). The main treatment technique used by individual water consumers is based on GAC adsorption in one or two steps (ηTCE = 99.4%, ηPCE = 99.8%, ηDCE = 46%), which can’t assure the required quality for drinking water, the residual concentrations being higher than MAC value (1,2DCE ≤ 10 mg/L; TCE ≤ 500 µg/L; PCE ≤ 0,5 µg/L). The applied treatment processes for advanced degradation of chlorinated ethenes are based on oxidation using photolysis or ozonation in different systems: UV alone, UV/H2O2, UV/O3, O3 alone, O3/ H2O2. Also, air stripping can be used for pollutants removal. The paper presents the experimental results obtained for the advanced removal of halogenated compounds by coupling air stripping with chemical oxidation, which can provide drinking water quality in compliance with legislation requirements.

Mine water from abandoned mines and spoil heaps from closed mining perimeter may generate significant surface water pollution. In Romania there are tens of sources with moderate to high contamination. Mine water flows have to be treated to meet national regulation NTPA 001/2005 for discharging in surface waters as any wastewater in any water body: low limits for heavy metals, but also for species considered benign to a certain level – calcium, magnesium and sulfate. By lime precipitation treatment, some CaSO4 can be formed, lowering the [SO42–] level, but the limit for sulfate will not be achieved, because the concentration correlated to gypsum solubility exceeds it by roughly three times. Sulfate precipitation as ettringite is a robust multi-stage technology (ECOIND- WISUTEC 2007–2012), but the costs are not reasonably sustainable for long term. Some approaches for modified technological flow-sheets and laboratory test result for the valorisation of reactive aluminium sources (e.g. mine water aluminium or flows with wasted aluminium).