All posts by simiecoind

Abstract:
The use of prehydrolized iron salts based coagulants as substitutes for aluminium based prehydrolized compounds for drinking water is a feasible alternative given the high removal efficiency of natural organic matter when treating water coming from various sources. By using prehydrolized coagulants, the removal efficiencies of the dissolved organic matter, (DOC), are 15-24% higher than in the case of using aluminium salts. On the other hand, as part of these experiments, the residual total organic carbon (TOC), is by 16.5% lower when prehydrolized iron based salts are used. Each situation is assessed in order to set up the specific working conditions when substitution of iron salts for aluminum compounds is suitable given the fact that even extremely small amounts of residual iron can colour the treated water.

Abstract:
Dissolved air flotation (DAF) has gained widespread usage over the last forty years for the removal of suspended solids, oils and greases, and biochemical oxygen demand from wastewater and other industrial process streams. DAF systems are frequently used to provide wastewater pretreatment, product recovery, and thickening of biological solids in industries ranging from food processing to pulp and paper to petrochemicals. Advances in the technology have expanded the range of applications for DAF; however, engineers and designers frequently use outdated and insufficient design data to design and specify DAF systems for industrial pretreatment.

Abstract:
The paper presents scientific results related to the establishment of water disinfection processes for Nistru River and highlights their effectiveness, using chlorine dioxide and sodium hypochlorite as disinfectants. It was established that from ecological and economical points of view, the most effective method of disinfection is the use of sodium hypochlorite. New catalysts have been synthesized based on carbon and mineral sorbents. The obtained catalysts were tested as solid supports to remove hydrogen sulfide from groundwater through aeration and oxidation processes. It was established that carbonic adsorbents made from nut shells and peach stones, oxidized and impregnated with ions of Cu2+, Mn2+ and Fe3+ show enhanced properties in the processes of oxidation and adsorption of hydrogen sulfide ions. Among mineral catalysts, the most prominent regarding the oxidation and adsorption capacity of hydrogen sulfide are solid media obtained by intercalation with aluminum oligomers and modified with manganese salts. Effectiveness of carbon adsorbent CAN-8- Mn2+-Fe3+ in the removal of hydrogen sulfide by physical and chemical methods was evaluated by semi-pilot scale studies using real groundwater from Hancesti. It was established that after 20 – 30 min of water treatment, the entire quantity of hydrogen sulfide was removed.

Abstract:
Aerobic granular sludge has several advantages over conventional activated sludge flocs such as fast settling ability, high biomass retention and ability to withstand high organic loading including potential toxic substrates, leading towards a compact reactor system – aerobic granular sludge sequential batch reactor (AGSBR). After successfully cultivating aerobic granules in SBR systems from flocculated activated sludge fed with synthetic medium with acetate as the sole carbon source or with real municipal wastewater, we investigated the possibility of AGSBR to simultaneously remove the organic loading, nitrogen and phosphorus content. The experiments were performed in a SBR reactor, at loadings rates of up to 3.0 kg m-3 day-1 COD and 0,2 kg m-3day-1 of N-NH4+. Compact granules with good settling ability were maintained during the experimental period and high (>95%) COD removal but insufficient global nitrogen (65%) and phosphorus (62%) removal efficiencies were registered. The size of the granule is closely related to the size of the anoxic zone: the lower the oxygen concentration or the bigger the granule, the larger the anoxic zone and thus, the larger the nitrogen and phosphorus removal capacity. In our study, the aeration intensity was maintained constant during the entire reaction period, in order to maintain the hydrodynamic shear forces within the reactor and implicitly the compact structure of the granules. The processes of COD removal, nitrification, denitrification and phosphorus removal can occur simultaneously in an aerobic granular sludge reactor fed with acetate. However, in case of higher concentrations of influent nitrogen and phosphorus different aeration or feeding strategies should be considered

Abstract:
Several kinds of wastewater are characterized by low carbon to nitrogen ratios and very high ammonia concentrations. Some examples are wastewater coming from sludge dewatering, fertilizer industry, explosive industry or some pharmaceutical processes. A feasible treatment of this kind of effluents is the combination of a partial nitritation, where 50% of ammonia is oxidized into nitrite in an aerobic reactor, and a subsequent anaerobic ammonium oxidation (Anammox), where ammonia is oxidized by nitrite in a second tank. This paper presents the results obtained in a nitritation reactor treating a wastewater from sludge dewatering with different ammonium concentrations in order to obtain a proper ammonium : nitrite ratio of 1:1 suitable for the anammox process and the results obtained during the start-up of an anammox reactor

Abstract:
Heavy metals are toxic substances which, at certain concentrations have serious impact upon water treatment plants. This leads to impaired biological processes of activated sludge, changes in composition of biocenosis and, eventually, no biological activity. The purpose of lab experiments was to test the influence of some heavy metals (cadmium, copper, zinc and nickel) at different concentrations, in batch bioreactors, with a retention time of wastewater of 24 hours. The inoculum was biological sludge and the bioreactors were fed with municipal wastewater supplemented with heavy metals. The community of ciliates is an indicator of the activity of biological sludge, therefore these were predominantly monitored throughout the experiment. The experimental results indicated that of all tested metals, cadmium at a concentration of 0.5-1 mg/l was mainly toxic, while zinc and nickel were less toxic, even at concentrations of 1.5-2.5 mg/l. The most sensitive species of protozoans to heavy metals were Chilodonella uncinata and Oxytricha sp., while the most resistant were the attached ciliates, like Opercularia coarctata and Vorticella microstoma. The attached ciliates resistant to high metal concentrations underwent morphological changes, like legthening of stem or forming buoyant individual cells or colonies. The study emphasized the presence and survival of ciliates in activated sludge in the presence of heavy metals at concentrations exceeding the admitted limits in WWTP influents.

Abstract:
This paper presents existent levels of soils pollution with organochlorinated pesticides, Lindane and DDT, in the proximity of two former Lindane and DDT suppliers (historical pollution). There were taken soil samples inside and outside the factories from different depths (20-150 cm). Analytical determination for both locations emphasized the following aspects:  there are two pollution sources: ex-Lindane/DDT installations and the landfills with HCH isomers and other chlorinated organic compounds;  the limit values stipulated by Order 756/1997 were exceeded (alert levels) outside the factories (HCH max =637 g/kg d.w. respectively (HCH max =264 g/kg d.w.) Microbiological load (mesophiles) was 2×108 and 4×107 CFU/g at 220C and 370C respectively (maximum values). DDT presence in soil was detected only in one studied case and the maximum value was 92 g DDX/kg d.w. (outside the factory). Inside the factory/landfill the concentrations levels of HCH isomers and DDX in soil were much higher.

Abstract:
In the field of remediation it has also become more common to combine two complimentary remediation technologies to present the best technical and economic approach to a given site. This article will examine the use of In Situ Chemical Oxidation (ISCO) utilising RemOx® L ISCO Reagent (sodium permanganate) for source area treatment used in combination with biostimulation for enhanced reductive dechlorination utilizing CAP18 ME® Anaerobic Bioremediation Product for polishing of the source area and treatment of the lower concentration downgradient plume at an industrial dry cleaning facility. The site is a closed industrial dry cleaning facility that is surrounded by both commercial and residential areas. Over the course of the facilities operation, the soil and groundwater at the site became contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE) which are common chlorinated dry cleaning agents.

Abstract:
The most preferred method of stabilization of sewage sludge is composting. It is apparently a simple process aimed at stabilization of organic matter – ripening, destruction of pathogenic organisms, production of an environmental friendly material which can be sold or used as fertilizer. To reach the above aims the sludge has to be mixed with structural materials in suitable proportion to obtain a C:N ratio of about 25:1. In practice, the most often used structural materials contain cellulose (i.e. wooden chips, sawdust, bark, straw, leaf litter, other vegetal wastes). The present study presents several composting experiments performed using as raw materials dewatered anaerobic digested sludge from a municipal WWTP, two different vegetal wastes (wood chips, straws, vine shoots) in different proportions and water in order to ensure a 50 to 70% humidity. The experiments were performed using aerated heap method; the heap is arranged on a porous layer, which is periodically aerated by a blower. Composting process evolution was verified during the whole period of 3 months of experimentation by online measurement of temperature, periodic pH and humidity monitoring and by weekly microscopic observations. The quality of the obtained compost was good, similar to commercial products used for pot-flowers, with heavy metal concentrations below the limits imposed by 344/2004 Order.

Abstract:
A sample of anaerobically digested sludge from an operation for municipal wastewater treatment in Bulgaria was characterized by relatively high contents of some heavy metals (mainly of iron, zinc, copper, manganese and chromium) and of some organochemical pollutants (mainly polyaromatic hydrocarbons and oil products). Some microorganisms which are indicators for the faecal pollution of the waters being treated such as Escherihia coli, Enterococcus faecalis and Streptococcus faecalis, were found in the samples, as well as some pathogenic microorganisms (related to the genus Clostridium) and eggs of helminths. The objective of this study was not only to remove the toxic pollutants from the activated sludge in connection with the relevant sanitary requirements but also to use the pretreated sludge as an amendment in agriculture and, having in mind the contents and the current prices of some heavy metals present in the activated sludge before treatment, to use it as a source of these metals. Copper and zinc were the most promising in this respect. Different treatment techniques were tested to achieve the objective mentioned above. The best results were obtained with sludge sample initially subjected to autoclaving and then leached by a mixed culture of moderately thermophilic chemolithotrophic bacteria. The addition of iron ions (mainly in the ferric state) and sulphuric acid from outside at the start of the leaching facilitated the growth of bacteria and the solubilization of metals. Leaching at 50 oC and an initial solid content of 20 % in the suspension resulted in high extractions of copper (98.8 %) and zinc (95.7 %) within 120 hours. The dissolved metals were selectively recovered from the pregnant leach solution by means of solvent extraction plus electrowining. The residual treated sludge contained no toxic chemical and biological pollutants in concentrations higher than the relevant permissible levels. At the same time, the bioassimilable forms of C, N, P, K and some essential microelements were still present in sufficient concentrations for utilization in agriculture.

Abstract:
To sustain healthy life in harmony with nature, it is extremely important to develop materials and processes that minimize a harmful influence on the environment. The feasibility of sludge recycling in the ceramic manufacture was evaluated through laboratory testing. Such residues have similar chemical and mineralogical composition with the raw mixture of the green ceramic body used in construction. Several ceramic masses with clay, sand and various proportion of sludge have been synthesized and then characterized by their physical-mechanical properties. The fineness of the clay, the main component of the green ceramic body, has been considered for every raw mixture. The proportion of the sludge waste addition depends of the clay fineness and the sintering capacity also, increases with the clay fineness. Ceramic properties, especially porosity, water adsorption and mechanical properties in the presence of small amounts of sludge have insignificant changes. The introduction of such waste into building ceramic matrix (bricks, tiles and plates) has a very good perspective.

Abstract:
The technology for processing waste plant material for their further use as food or dietary products “Lignin-Cellulose Sorbents” and functional foods “CELISORB” was developed. It was studied the organoleptic and physicochemical parameters of these materials and was shown that they were promising materials for use in medicine and food industry as (entero)sorbents, antioxidants and dietary supplements, which could solve many problems of internal ecology of organism (endoecology) and health of people. Integrated radiometric, laboratory and clinical research were carried out. Clinical studies were done to assess the therapeutic and decorporative efficacy relative to 137Cs for children aged 7-17 residing in territories contaminated with radionuclides.

Abstract:
The wastewater results from different foods industry are generally characterized by a high organic load, far above limits discharge referred to legislation. In particular the wastewater results from different technological phases of milk industry processing, contain high quantities of organic compounds, especially proteins (caseine, β-lactoglobuline, α-lactalbumine, serumalbumine, immunoglobuline), lipide (mono, di and triacilglicerides, free fat acids, phospholipids) and disaccharides class (especially lactose). In the treatment processes, the membrane techniques – microfiltration, ultrafiltration, reverse osmosis – are frequently used for their advantages: are continuous processes, the energetic consumption is very low, not implies temperature and phase changes, not uses chemicals adjuvant, occur in modular equipment. The paper present the experimental results obtained in the ultrafiltration process of a wastewater from milk industry processing- washing the reactors from production of yoghurt. The aim of the experiments was to studied the correlation between the membrane characteristics and the reduction of the organic compounds from the wastewater. 2 composite ultrafiltration membranes were used, polysulphone-polyaniline types, different by monomer used on policondensation chemical reaction in porous structure of the base polymer. The experimental setup that has been used was the KMS Laboratory Cell CF-1 (Koch-Membrane – Germany) ensuring a tangential flow mode in separated process. The following indicators were analyzed from the water samples (the feed wastewater, the permeate and the concentrate): TOC, BOD, COD, total nitrogen, protein contents, conductivity. In the same time were studied the hydrodynamic, electroconductive and structural characteristics of the membranes. Relevant in these experiments were: – reduction the proteine contents in permeate to 42% – higher reduction of the DOC contents in permeate to 92% The BOD/COD ratio in the permeate samples was above 0,3, which indicate the remanent biodegradable characteristics. In this case its possible to introduce the water on the biological treatment setup improving their performances.

Abstract:
The paper presents some relevant aspects related to the influence of pollution matrix specific to the groundwater supplies, upon the treatment technologies applied in order to remove the inorganic nitrogen – based compounds (ammonium, nitrite, nitrate ions). The main association of ammonium (NH4+) with inorganic/organic pollutants in groundwater are, as follows:  NH4+ and metallic ions (Mn  Fe);  NH4+ and sulphur derivatives (S2-, S2O32-, SO32-);  NH4+ and nitrite/nitrate ions (NO2-/ NO3-);  NH4+ and natural organic matter (NOM – THMs precursors) in the presence of bromide ion (Br-). Also, the concentration levels of nitrogen – based compounds and associated pollutants are very important in the selection of suitable treatment procedures, including the succession of treatment steps. The treatment technologies developed for NH4+ and NO3- ions removal from groundwater supplies have as specific steps: breakpoint chlorination (NH4+) or biological nitrification (NH4+) and denitrification (NO2-/ NO3-) processes. Among the main problems specific for the most applied technology at industrial level for NH4+  oxidizable pollutants removal (one step chlorination), are mentioned:  low treatment efficiency (NH4+, S2-);  generation of trihalometanes (THMs), especially brominated ones, with unpleasant consequence upon the treated water quality, which is not proper for human consumption.

Abstract:
The low-pressure system, also known as vacuum system or vacuum sewer system contains closed pipeline networks without manholes. Vacuum sewer systems are essentially mechanized systems of wastewater transport. Unlike typical gravity sewers, it uses differential air pressure to transport the wastewater and all the sewer mains are under vacuum (under negative pressure). The high transport velocity of the air/water-mixture in the vacuum pipelines prevents sediments. An outlet of wastewater is excluded due to the vacuum occurring inside the system. The system is more economical and efficient compared to the classical gravitational sewage network. Normally the drainage procedure serves as a collection of wastewater in separate systems. Though, vacuum sewer line may be laid in the same trench together with water supply lines and storm water drainage according to the German guideline DWA-A 116-1. In this case, there shall be no physical connections between a public or private potable water supply system and a sewer. The vacuum technology is a special drainage procedure which might – under certain circumstances – be considerably cheaper than the conventional gravity lines sewage system. Investments costs can be considerably lower in comparison with other drainage procedures.