Helge Liltved

Inactivation of bacterial and viral fish pathogens by ozonation or UV irradiation in water of different salinity

Abstract Bacterial and viral fish pathogens were exposed to ozone or ultraviolet (UV) irradiation in laboratory batch systems. Inactivation curves were made for Aeromonas salmonicida subsp. salmonicida, Vibrio anguillarum, Vibrio salmonicida, Yersinia ruckeri and the infectious pancreatic necrosis virus (IPNV) in ozonated lake, brackish and sea water at 9–12°C. The four bacteria tested were inactivated by 99·99% (4 log reductions in viable count) in all three waters within 180s at residual ozone concentrations of 0·15-0·20 mg/liter measured by the indigo colorimetric method. After establishing these residuals, the differences in water salinity did not cause any substantial differences in bactericidal activity of ozone, illustrating the usefulness of concentration measurements by the indigo colorimetric method to predict inactivation also in saline waters. The rate of bacterial inactivation was fast during the first 60 s in all three waters. After that point the slope of the curves levelled off. This observation was explained by loss of ozone and reduced bactericidal activity during the course of the experiments. IPNV was inactivated (99·99%) in all three waters within 60 s when exposed to 0·10-0·20 mg/liter residual ozone. V. anguillarum, V. salmonicida, Y. ruckeri and IPNV were UV irradiated in brackish water at room temperature. An UV dose of 2·7 m Ws/cm 2 resulted in 99·999% (5 log) reduction in viable count for all three bacteria. IPNV was much more resistant to irradiation than the bacteria. An average UV dose of 122 mWs/cm 2 was required for 99·9% (3 log) reduction in virus titer.

Diurnal variations in the occurrence and the fate of hormones and antibiotics in activated sludge wastewater treatment in Oslo, Norway

We present an assessment of the dynamics in the influent concentration of hormones (estrone, estriol) and antibiotics (trimethoprim, sulfamethoxazole, tetracycline, ciprofloxacin) in the liquid phase including the efficiency of biological municipal wastewater treatment. The concentration of estradiol, 17-alpha-ethinylestradiol, doxycycline, oxytetracycline, demeclocycline, chlortetracycline, cefuroxime, cyclophosphamide, and ifosfamide were below the limit of detection in all of the sewage samples collected within this study. Two different types of diurnal variation pattern were identified in the influent mass loads of selected antibiotics and hormones that effectively correlate with daily drug administration patterns and with the expected maximum human hormone release, respectively. The occurrence of natural hormones and antimicrobials, administered every 12 hours, shows a daily trend of decreasing contaminant mass load, having the maximum values in the morning hours. The occurrence of antibiotics, typically administered every 8 hours, indicates a daily peak value in samples collected under the highest hydraulic loading. The efficiency of biological removal of both hormones and antibiotics is shown to be limited. Compared to the values obtained in the influent samples, increased concentrations are observed in the biologically treated effluent for trimethoprim, sulfamethoxazole and ciprofloxacin, mainly as a result of deconjugation processes. Ciprofloxacin is shown as the predominant antimicrobial compound in the effluent, and it is present at quantities approximately 10 fold greater than the total mass of the other of the compounds due to poor removal efficiency and alternating solid-liquid partitioning behaviour. Our results suggest that, to increase the micro-pollutant removal and the chemical dosing efficiency in enhanced tertiary treatment, significant benefits can be derived from the optimisation of reactor design and the development of control schemes that accounts for diurnal secondary effluent micro-pollutant and hydraulic loading patterns.

A system for the treatment of sludge from land-based fish-farms

Abstract This paper describes both an experimental and a commercial-scale system for sludge dewatering and stabilisation. In the experimental system, back-wash water from rotating disk microsieves was settled in a conical sedimentation tank. This tank functioned well, commonly removing more than 75–80 % of the solids, at an overflow rate of 1.0–2.7 m·h−1. The hydraulic load was maintained low, so treatment efficiency was significantly positively influenced by inlet concentration and not inflow rate. Lime was added to the settled sludge. More than 99.9 % of the pathogenic viruses and bacteria studied were killed within 7 days at pH 12. In the commercial system, a newly developed combined effluent treatment and sludge processing system, was located in a large Norwegian salmon (Salmo salar) smolt farm. Four drum microsieves were used to separate particles from the primary effluent flow. The back-wash water, amounting to a maximum of 0.3 % of the 30–35 m3·min−1 primary flow, was dewatered using another drum microsieve. Dewatered back-wash water from this sieve was pumped to a sedimentation tank with a top surface area of 3.3 m2 and a volume of 5.5 m3. This system produced on average 0.7 L settled sludge containing ca. 10 % dry matter per kg of feed supplied. Sludge tapped from the bottom of the sedimentation tank was stabilised by mixing with lime. This system produced on average 0.7 L settled sludge containing ca. 10 % dry matter per kg of feed supplied. After stabilisation, the stored sludge was diluted with cattle manure and spread on agricultural land. The primary treated effluent was discharged into the receiving marine water body. The running costs of effluent and sludge treatment, including sieving, settling and stabilisation, amounted to US

Disinfection by-products and ecotoxicity of ballast water after oxidative treatment – Results and experiences from seven years of full-scale testing of ballast water management systems

0.056 per smolt produced, or about 5 % of the total production costs. In the recipient, no settled solids were detected on the seabed at the outlet point of the treated effluent.

Influence of liquid holding recovery and photoreactivation on survival of ultraviolet-irradiated fish pathogenic bacteria

Since 2005, five different ballast water management systems (BWMSs) based on chlorination treatment have been tested by Norwegian Institute for Water Research (NIVA) according to guidelines from the International Maritime Organization (IMO). 25% and >50% of all the tested discharge samples exhibited acute and chronic toxic effects on algae, respectively. In most cases this toxicity was plausibly caused by a high free residual oxidant (FRO) level (>0.08 mg Cl/l). Of the 22 disinfection by-products (DBPs) that were identified in treated water at discharge, four compounds were at times found at concentrations that may pose a risk to the local aquatic environment. However, there seemed to be no clear indication that the measured DBP concentrations contributed to the observed algal toxicity. The addition of methylcellulose instead of lignin in the test water to comply with IMO requirements seemed to limit the formation of DBP.

Climate change impacts on activated sludge wastewater treatment: a case study from Norway

Abstract Survival of the fish pathogens Aeromonas salmonicida subsp. salmonicida, Vibrio anguillarum, and Yersinia ruckeri, when subjected to various post-u.v. irradiation treatments, was investigated in a laboratory model system. In A. salmonicida, 99.9% inactivation doses had to be increased from (a) 3.2 mWscm−2 in the case of no post-irradiation recovery treatment to (b) 8.1 mWscm−2 if liquid holding in nutrient-free buffer in the dark for 48 h was applied before plating, (c) 9.5 mWscm−2 with visible light illumination at 1500 lx for 8 h and (d) 10.6 mWscm−2 with illumination followed by liquid holding. The corresponding figures for V. anguillarum were 2.8, 8.1, 6.3 and 13.4 mWscm−2 and for Y. ruckeri 1.2, 5.3, 4.9 and 8.5 mWscm−2. On combined treatment, the latter two species showed distinct plateaus of no or very low sensitivities to increased irradiation doses, while this feature was not evident in A. salmonicida. Complete liquid holding recovery demanded from 48 to more than 72 h at 22°C, while photoreactivation was completed within 4–6 h in all three species at the same temperature. If illumination intensity was reduced from 1500 to 150 lx, recovery time was approximately doubled in A. salmonicida. During post-irradiation dark incubation photoreactivating capacity was lost within approximately 15 h. It is concluded that the potential of fish pathogenic bacteria for liquid holding recovery and photoreactivation should be taken into consideration when assessing the efficiency of u.v. disinfection of aquacultural water. Particular concern should be aimed at recovery processes after discharge to recipient water.

Impact of rainfall on microbial contamination of surface water

We present an investigation on climate change effects on a wastewater treatment system that receive sewage collected in a combined sewer system in Oslo, Norway, during winter operation. Results obtained, by contrasting meteorological data with sewage data, show that wastewater treatment plant (WWTP) influent flow rates are significantly increased during temporary snow melting periods above a critical daily air mean temperature of approx. -1.5 degrees C degree (T(Crit)) identified in the area. In order to assess melting patterns, the number of days above and below T(Crit) was assessed, and the annual number of melting periods was additionally evaluated using meteorological data obtained in the last decade. A striking thing about the daily air temperature pattern is that, despite the progressively warmer winter temperatures in the last decade, an increasing number of days with temperatures below -1.5 degrees C could be observed. The frequency of melting periods is shown to increase in wintertime, and it is identified as an additional climate change related factor in the Oslo region. We demonstrate that these impacts can deteriorate the WWTP operation through progressively increasing the relative frequencies of very high influent flow rate and of the very low influent sewage temperature. Such climate change related effects on sewage treatment processes can be characterised as shock-conditions, i.e. significant changes in a systems boundary conditions, occurring in a relatively short period of time. In the six year period examined, biological nitrogen removal and secondary clarification processes are shown to be significantly affected by the climate factors. A striking thing about using the state-of-the-art mathematical models of wastewater treatment processes in decision support systems is their inability of describing, and thus predicting the effects of such shock-loading events, as they have not been studied so far. Adaptation and optimisation of process models, also for use in design, optimisation as well as in real-time automation and process control schemes, are thus critical to meet the challenges of climatic changes in the future.

The BIOZO process - a biofilm system combined with ozonation: occurrence of xenobiotic organic micro-pollutants in and removal of polycyclic aromatic hydrocarbons and nitrogen from landfill leachate.

Purpose – Increased annual precipitation and more frequent episodes with heavy precipitation are expected in Norway due to climate change. The purpose of this paper is to use two case studies to investigate effects of precipitation on the amounts of faecal indicator bacteria and parasitic protozoa (Cryptosporidium and Giardia) loaded to surface waters from catchment areas exposed to different faecal sources.Design/methodology/approach – In the first case study, the loads of faecal indicator bacteria and Cryptosporidium and Giardia, were investigated in relation to precipitation in a stream from a small valley where cattle and sheep are grazed. In the second case study, historical data (monthly values from 2004‐2009) regarding faecal coliforms and water flow in five tributaries (urban and rural) of a lake used as a drinking water source, were used for calculating loads of faecal indicator bacteria. These loads were evaluated in relation to historical data on precipitation. Additional sampling during/after ...

Effect of water treatment on the growth potential of Vibrio cholerae and Vibrio parahaemolyticus in seawater.

We present an assessment of xenobiotic organic micro-pollutants (XOM) occurrence and removal of polycyclic aromatic hydrocarbons (PAHs) in a novel biofilm system combined with ozonation, the BIOZO concept, treating partly stabilised landfill leachate. A novel, staged moving-bed biofilm reactor (SMBBR) design was implemented in laboratory- and pilot-scale, and the PAHs removal efficiency of controlled ozonation was assessed installing the ozonation step in the nitrate recirculation line (Position 1) or between the pre-anoxic and aerobic zones (Position 2). COD removal in a laboratory- and in a pilot-scale SMBBR system with and without ozonation is additionally addressed. Results obtained in a screening study (GC-ToF-MS) were used to compile a priority list of XOMs in leachate based on relative occurrence, showing PAHs as the predominant fraction. Biological treatment is shown to be an effective means to remove PAHs detected in the aqueous phase. PAH removal takes in most part place in the pre-anoxic zone, thereby decreasing toxicity exhibited by PAH on autotrophic nitrifier bacteria in the aerobic zone. Ozonation installed in Position 2 is shown to be superior over Position I in terms of COD, PAH and nitrogen removal efficiencies. We additionally demonstrate the potential of intermittent sludge ozonation as a means to decrease PAH concentrations in sludge wasted and to improve nitrogen removal in the BIOZO system.

Screening as a method for removal of parasites from inlet water to fish farms.

In laboratory experiments we added Vibrio cholerae and Vibrio parahaemolyticus to bottles with seawater previously treated by filtration, UV, chlorine or ozone. The purpose was to investigate the influence of different treatment techniques on the growth potential of these bacteria in simulated ballast water tanks. Residual oxidants were removed before inoculation, and the bottles were incubated at 21 ± 1 °C. The growth potential of the vibrios was investigated in two different experimental setups, i.e. in presence and absence of added natural microorganisms. In general, V. cholerae and V. parahaemolyticus rapidly lost their culturability after inoculation and storage in untreated seawater, but showed increased survival or growth in the treated water. Highest growth was observed in water previously exposed to high concentrations of ozone. Addition of natural microorganisms reduced the growth of V. cholerae and V. parahaemolyticus.