R. M. A. Napoli

Wastewater disinfection by combination of ultrasound and ultraviolet irradiation

Reclamation and reuse of wastewater is one of the most effective ways to alleviate water resource scarcity. In many countries very stringent limit for chlorination by-products such as trihalomethanes has been set for wastewater reuse. Accordingly, the use of alternative oxidation/disinfection systems should be evaluated as possible alternative to chlorine. Recently ultrasound (US) was found to be effective as pre-treatment for wastewater disinfection by UV irradiation. The aim of this work is to investigate the wastewater advanced treatment by simultaneous combination of UV and US in terms of bacteria inactivation (Total coliform and Escherichia coli) at pilot-scale. The pilot plant was composed of two reactors: US-UV reactor and UV reactor. The influence of different reaction times, respective US and UV dose and synergistic effect was tested and discussed for two different kinds of municipal wastewater. An important enhancement of UV disinfection ability has been observed in presence of US, especially with wastewater characterized by low transmittance. In particular the inactivation was greater for T. coliform than for E. coli. Furthermore, the results obtained showed also that the fouling formation on the lamps was slower in US-UV reactor than in UV reactor both with and without solar radiation.

Regrowth Evaluation of Coliform Bacteria Injured by Low Chlorine Doses Using Selective and Nonselective Media

Abstract In this study, the repairing capacity of coliform bacteria injured by chlorine is determined. Chlorine doses from 0.014 to 0.070 mg L−1 were used in according to frequency (up to 38%) of chlorine concentrations detected in a drinking water distribution network, adopted as case study. m-Endo (selective) and m-T7 (nonselective) cultivation media are used. Bacterial regrowth was detected up to 0.035 mg L−1 of chlorine for 4 h of incubation. The coliform bacteria were not able to regrowth when the dose of chlorine increased to 0.07 mg L−1. Bacterial regrowth increased by increasing C:N ratio from 1:40 to 11:40. m-T7 (nonselective) medium allowed to detect bacterial regrowth also for lower incubation periods. Chlorine doses higher than 0.2 mg L−1 dose at water source with a low total organic carbon (TOC) content are recommended to control bacterial regrowth in the distribution network.

Combined Carbonaceous Removal and Nitrification with Biological Aerated Filters

Abstract This paper describes the use of a submerged biological aerated filter (BAFs), on a pilot plant scale, in the secondary nitrification of low strength domestic wastewater. The results, obtained throughout three months of tests, confirmed the ability of BAFs to obtain simultaneous carbonaceous removal and nitrification. In fact, after a start-up period of 5 weeks, a remarkable steady state condition in the removal of suspended solids (TSS), chemical oxygen demand (COD) and nitrification was reached. For a hydraulic loading rate of 1.6 m3 m−2 h−1, the mean efficiency of the process in the removal of TSS and COD was 85% and 83% respectively. Mean concentrations in the influent flow of around 114 mgTSS/L and 140 mgCOD/L were reduced to average values of below 17 mgTSS/L and 25 mgCOD/L. Secondary nitrification was achieved with a mean efficiency of 85% for a mean volumetric loads of 0.45 kgN-Namm m−3 d−1 (25°C). Through an intensive activity of nitrification, in the steady state condition, mean influent concentrations of around 12 mgN-Namm/L were reduced to average values of below 2 mgN-Namm/L. The removal loading rate increased linearly with the applied loading rate for volumetric loads of up to 0.7 kgN-Namm m−3 d−1. The nitrification was not sensitive to the applied COD loads because of the low level of carbon substrate.

Occurrence and Measurements of Organic Xenobiotic Compounds in Harbour and Coastal Sediments

The present chapter focuses on the identification of sources and fluxes of xenobiotic compounds in marine sediments to set strategies for minimizing impacts on the human life and environment. It is generally accepted that sediments constitute a sink for the more hydrophobic compounds, posing an unacceptable risk to aquatic biota, in which these compounds can bioaccumulate, and to human health through the ingestion of contaminated fish and shellfish.

Groundwater quality monitoring in a rural area

Abstract The paper describes results of monitoring activities of groundwater in a rural area carried out to verify the impact on water quality in an uncontaminated area resulting from the initiation of an atmospheric pollution source. Significant emissions of nitrogen oxides from the pollution source resulted in particular attention to verify increase of nitrate concentrations in monitored water. Over 10,000 analytical tests including several chemical parameters were conducted in the full monitoring period. In the paper, a first reading of data, graphical trends and nonparametric statistical analysis of resultant water quality, are presented. Measured values for nitrates, nitrites, hardness, alcalinity and pH showed poor variability during the entire period. Checked parameters were in the usual ranges of uncontaminated rural areas and comparisons between meaningful values of the periods ante operam and post operam do not show any degradation of water quality following the atmospheric pollution source activity. Nitrites are occasionally found in some spring water due to organic pollution, confirmed by randomness of presences detected.

WATER TREATMENT IN REMOTE AND RURAL AREAS: A CONCEPTUAL SCREENING PROTOCOL FOR APPROPRIATE POU/POE TECHNOLOGIES

Abstract Small communities and individual dwellers in rural areas face the burden of obtaining safe drinking water supplies with limited financial and technical resources. Novel applications of proven drinking water treatment technologies at the point-of-use/point-of-entry (POU/POE) are often seen as an effective and economical solution to production of safe drinking water in rural areas. A brief review of the different technologies is here presented, with respect to maintenance requirements and costs. A conceptual screening protocol for the selection of appropriate technologies is then proposed, which incorporates the site specific factors and constraints that may affect the decision process .