Ozonation and biological activated carbon filtration of wastewater treatment plant effluents.

This study investigates the fate of trace organic chemicals (TrOCs) in three full-scale reclamation plants using ozonation followed by biological activated carbon (BAC) filtration to treat wastewater treatment plant effluents. Chemical analysis was used to quantify a wide range of TrOCs and combined with bioanalytical tools to assess non-specific toxicity (Microtox assay) and estrogenicity (E-SCREEN assay). Limited dissolved organic carbon (DOC) removal (<10%) was observed in the ozonation stages showing that oxidation leads to the formation of transformation products rather than mineralization. The quantified TrOCs were removed to a degree highly dependent on the compounds' structures and the specific ozone dose (mg(O3) mg(DOC)(-1)). Non-specific toxicity was reduced by 31-39%, demonstrating that the mixture of remaining parent compounds and their transformation products as well as newly formed oxidation by-products had an overall lower toxic potential than the mixture of parent compounds. Estrogenicity was reduced by more than 87% indicating that the transformation products of the estrogenic chemicals lost their specific toxicity potential. The subsequent BAC filtration removed between 20 and 50% of the DOC depending on the plant configuration, likely due to biodegradation of organic matter. The filtration was also able to reduce the concentrations of most of the remaining TrOCs by up to 99%, and reduce non-specific toxicity by 33-54%. Overall, the combination of ozonation and BAC filtration can achieve removals of 50% for DOC and more than 90% for a wide range of TrOCs as well as a reduction of 70% of non-specific toxicity and more than 95% of estrogenicity. This process combination is therefore suggested as an effective barrier to reduce the discharge of TrOCs into the environment or their presence in water recycling schemes.

Biofiltration of wastewater treatment plant effluent: effective removal of pharmaceuticals and personal care products and reduction of toxicity.

This study investigates biofiltration for the removal of dissolved organic carbon (DOC), pharmaceuticals and personal care products (PPCPs), and for the reduction of non-specific toxicity expressed as baseline toxicity equivalent concentration (baseline-TEQ). Two filtering media, sand and granular activated carbon, were tested. The influence of pre-ozonation and empty-bed contact time (EBCT, from 30 to 120 min) was determined. The experiments were performed at a pilot-scale with real WWTP effluent. A previous study showed that biological activity had developed on the filtering media and dissolved organic removal had reached a steady state before sampling commenced. The results show that biological activated carbon (BAC) has a good potential for the removal of DOC (35-60%), PPCPs (>90%) and baseline-TEQ (28-68%) even without pre-ozonation. On the contrary, the sand shows limited improvement of effluent quality. Varying the EBCT does not influence the performance of the BAC filters; however, dissolved oxygen concentration could be a limiting factor. The performances of the BAC filters were stable for over two years suggesting that the main mechanism of organic matter and PPCPs removal is biodegradation. It is concluded that BAC filtration without pre-ozonation could be implemented as a low cost advanced treatment option to improve WWTP effluent chemical quality.

Monitoring the biological activity of micropollutants during advanced wastewater treatment with ozonation and activated carbon filtration.

A bioanalytical test battery was used to monitor the removal efficiency of organic micropollutants during advanced wastewater treatment in the South Caboolture Water Reclamation Plant, Queensland, Australia. This plant treats effluent from a conventional sewage treatment plant for industrial water reuse. The aqueous samples were enriched using solid-phase extraction to separate some organic micropollutants of interest from metals, nutrients and matrix components. The bioassays were chosen to provide information on groups of chemicals with a common mode of toxic action. Therefore they can be considered as sum indicators to detect certain relevant groups of chemicals, not as the most ecologically or human health relevant endpoints. The baseline toxicity was quantified with the bioluminescence inhibition test using the marine bacterium Vibrio fischeri. The specific modes of toxic action that were targeted with five additional bioassays included aspects of estrogenicity, dioxin-like activity, genotoxicity, neurotoxicity, and phytotoxicity. While the accompanying publication discusses the treatment steps in more detail by drawing from the results of chemical analysis as well as the bioanalytical results, here we focus on the applicability and limitations of using bioassays for the purpose of determining the treatment efficacy of advanced water treatment and for water quality assessment in general. Results are reported in toxic equivalent concentrations (TEQ), that is, the concentration of a reference compound required to elicit the same response as the unknown and unidentified mixture of micropollutants actually present. TEQ proved to be useful and easily communicable despite some limitations and uncertainties in their derivation based on the mixture toxicity theory. The results obtained were reproducible, robust and sensitive. The TEQ in the influent ranged in the same order of magnitude as typically seen in effluents of conventional sewage treatment plants. In the initial steps of the treatment chain, no significant degradation of micropollutants was observed, and the high levels of dissolved organic carbon probably affected the outcome of the bioassays. The steps of coagulation/flocculation/dissolved air flotation/sand filtration and ozonation decreased the effect-based micropollutant burden significantly.

Removal of micropollutants and reduction of biological activity in a full scale reclamation plant using ozonation and activated carbon filtration.

Pharmaceutical compounds are found in secondary treated effluents up to microg L(-1) levels and therefore discharged into surface waters. Since the long term effects of these compounds on the environment and human health are, to date, largely unknown, implementation of advanced treatment of wastewaters is envisaged to reduce their discharge. This is of particular relevance where surface waters are used as drinking water sources and when considering indirect potable reuse. This study aimed at assessing the removal of organic micropollutants and the concurrent reduction of their biological activity in a full scale reclamation plant treating secondary effluent. The treatment consists of 6 stages: denitrification, pre-ozonation, coagulation/flocculation/dissolved air flotation and filtration (DAFF), main ozonation, activated carbon filtration and final ozonation for disinfection. For that purpose, representative 24-hour composite samples were collected after each stage. The occurrence of 85 compounds was monitored by LC/MS-MS. A battery of 6 bioassays was also used as a complementary tool to evaluate non-specific toxicity and 5 specific toxic modes of action. Results show that, among the 54 micropollutants quantified in the influent water, 50 were removed to below their limit of quantification representing more than 90% of concentration reduction. Biological activity was reduced, depending on the specific response that was assessed, from a minimum of 62% (AhR response) to more than 99% (estrogenicity). The key processes responsible for the plant's performances were the coagulation/flocculation/DAFF, main ozonation and activated carbon filtration. The effect of these 3 processes varied from one compound or bioassay to another but their combination was almost totally responsible for the overall observed reduction. Bioassays yielded complementary information, e.g. estrogenic compounds were not detected in the secondary effluent by chemical analysis, but the samples had an estrogenic effect. The main ozonation formed oxidation by-products of the organic micropollutants but decreased the level of non-specific toxicity and other specific toxic modes of action, demonstrating that the mixture of oxidation by-products was less potent than the mixture of the parent compounds for the considered effects.

[Comprehensive care of patients with dysgnathic defects at the dental department of the regional hospital with polyclinic in Ceské Budejovice]. / Kompliexní péce o pacienty dysgnátní vadou na stomatologickém oddelení KNsP Ceské Budejovice.

The authors describe in the form of case- histories the comprehensive care of patients with dysgnatic defects at the dental department of the hospital with policlinic in Ceské Budejovice. The collaboration of orthodontists, surgeons and prosthetists is involved in different combinations. As an example the mention the collaboration during the therapeutic procedure used in a 25-year-old female patient with a protrusion defect, deep occlusion and crowding in the upper frontal section.