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Sludge reuse is one of the main challenges of waste management and an action with environmentally consequences that must be kept under control. The progress of civilization leaded to the globally increase of sludge production. WWTPs treatment technologies, sludge disposal/recovery and also quality control and toxicological involvements became parts of strategical actions at international level. The main disposal strategies for sludge management include agriculture or landscaping purposes, or final disposal. The accepted international policy is sludge application as organic fertilizer in agriculture. In this context, the research paper presents laboratory data used in decisional actions for the sludge land disposal. The study covers physical and chemical characterization of sludge resulted from Focsani WWTP, agriculture soil collected from around of Focsani WWTP and their leachates in compliance with national norms. In addition, the toxic effects on soil organisms (plants) were evaluated. Generally, soil and sludge quality meet the normed criteria for minimizing the potential impact on the environment. The leachate experiments showed the non-hazardous character on the soil properties of groundwater, the predicted impact being insignificant for the tested sludge / soil chemical composition. Ecotoxicological assessment of stabilized sludge showed inhibitory effects in the range of 25% to 100% on seed germination and root growth of plants Sorghum sacharatum, Sinapis alba and Lepidium sativum. In the range of 1% or 5% no significant inhibitory effect of sludge on plants growth was observed. Sorghum sacharatum showed the best growth, but there were no relevant differences between species. A saftey dose of 5% sludge mixed with agriculture soil (250 tonnes per hectare) was established. A monitoring program of sludge / soil quality and also ecotoxic evaluation was recomanded for the saftey of crops growth and health of living organisms including humans.

Collagen production is generating wastewater with high organic loading. This type of wastewater is still containing valuable compounds that can be reused in other applications. In order to investigate the possibility to recover and reuse these compounds the membrane based processes were investigated. Four types of commercial available membranes were characterised and then used to recover the proteins. The results proved that membrane based processes represent a viable alternative to treatment of wastewater generated by collagen production facilities when recovery of valuable compounds is envisaged. It has to be stressed that on the other hand only membrane processes do not assure too reach the quality norms imposed by the legislation for treated wastewater discharge into sewerage systems or natural receivers. Therefore, when proteins recovery and reuse is wanted, the membrane processes represent only the first step of wastewater treatment and should be followed by biological processes in order to obtain the organic loading quality indicators required for wastewater treatment plants discharges.

The influence of attached biomass bioreactor types on the denitrification process using a low-pitched groundwater containing nitrates was studied. Two types of fixed-bed and fluidized-bed biofilm reactors, equipped with expanded clay granular filler, with a particle size fraction of 2-5 mm were used. The nitrite and nitrate concentrations in the inflow and outflow of the two bioreactors were analytically determined. Based on the obtained concentration values, the denitrification rates were calculated, ranging between 1275�1387 g NO3-N/m3/day in the case of the fixed bioreactor and between 3390�3867 g NO3-N/m3/day in the case of the fluidized bed bioreactor.

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 were 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 are needed.