Objective
- Comparison of different disinfecting technologies in terms of germicidal effect as well as formation of harmful by-products;
- Investigation of health implications and waterborne disease spread out by partially disinfected wastewater with special attention to epidemiological and toxic effects on aquatic life and humans;
- Evaluation of low-cost technology systems of wastewater treatment for agricultural reuse appropriate to Mediterranean Countries;
- Optimisation of schemes for wastewater utilisation in agriculture by reference to crops, pedology, groundwater vulnerability, irrigation methods and management aspects.
Italy
- Till the end of 1996, the investigation of UV disinfection effectiveness for treating clariflocculated and filtered activated sludge secondary effluents from West Bari Municipal Wastewater Treatment plant has been carried out by a purposely built 100m3/h pilot plant. The main results achieved at the end of such investigation have been the following :
- an UV dose of approximately 100 MWs/cm2 is necessary to achieve the target total coliforms limit (2 CFU/100ml);
- the quality of the UV treated effluents result in compliance with Italian and International Standards for agricultural reuse;
- at least under the investigated condition and analytical procedures, it seems that UV-promoted formation of disinfection by-products does not occur as indicated by both chemical and toxicological evidences.
- As for the fundamental studies aimed to quantify the real UV dose provided to UV treated wastewater, by an advanced laser-device, under fixed operative conditions (water flow-rate and quality), the validity of two theoretical models (P55 and RTD) has been assessed. The most significant result obtained during the reference period has demonstrated that the real UV dose inside the investigated UV reactor is by far to be constant but strongly depends upon the wastewater hydrodynamics and quality, the distance from the UV source, and the type of UV lamps configuration (submerged or not).
Israel
- There are two main parts of the results :
First : the die-off kinetics of E. coli-B and MS2 bacteriophage upon exposure to hydrogen peroxide alone and/or with silver or copper ions.
Second : the kinetics of toxicity of peroxide and silver, combined or separated on E. coli K12 (a wild type strain) and on the luminescence of recombinant E. Coli K12. The induction of stress genes by the above agents is also tested.
The results of the first part are as follows :
- The combination of peroxide and silver ions, rather than each one separately was the most effective in inactivating E. coli-B; however, silver ions were more effective than peroxide;
- A reduction of more than 5 logs in the viability of E. coli-B was achieved after 5 hour exposure to silver ions, as opposed to 24 hours exposure to peroxide in order to obtain a similar die-off;
- Silver ions were more efficient at pH-9 while peroxide was not pH dependent at the pHs tested (6.0 7.0 and 9.0);
- Preliminary results showed that copper, when used in combination of peroxide, was most effective at 250 and 500 ppb, causing about 3 log reduction in E. coli after 2hr. exposure;
- MS2, in contrast to E. coli-B was susceptible to peroxide, where as silver ions were ineffective in killing the virus at both high and low pH;
- In general, a 3 log reduction, using 30 ppm peroxide and 30 ppb silver ions, required an exposure of 77 min for E. coli-B and 802 min for MS2.
The results of the second part are as follows :
- A concentration combination 30 ppm peroxide and 30 ppb silver exhibited a mild toxicity against E. coli K-12 (approx. 2-3 log reduction after an exposure of 60 min);
- A synergistic effect on the viability of E. coli K-12, and on the luminescence of recombinant E. coli, in which luminescence serves as a reporter for the general metabolic state of the bacteria was found;
- Using bacterial luminescence as a reporter system for stress gene expression revealed that peroxide induces a wide array of stress responses (DNA, protein damages and oxidative ones) while silver induced stresses responding to protein damages. It is possible that the combined toxic effect of these agents is related to elevated damages to cellular protein moieties.
- Concluding this stage of the study it seems that the combination of peroxide and silver can serve as a secondary long acting residual disinfectant.
Morocco
- Apparent removal rates are not convenient for comparison between different systems covering different areas of land and receiving different wastewater flows. A mode of expression of the results has been adopted which relates the concentration of FC removed to the area of land occupied by the treatment train and to the flow of wastewater applied per daily, a factor of specificity that takes into account the area and the daily flow.
- In this way, large differences in the FC specific removal rates between the HARP and the WASP trains are observed on the basis of the chlorophyll content. An improvement of 1.5 times is recorded for the maturation and the facultative stages. We recorded respectively 4 and 1.7 times in favour of the HRAP. This FC removal improvement is correlated with the chlorophyll a content.
- The same effect of the chlorophyll as those shown on FC removal are shown on nitrogen and orthophosphate removals. They show the superiority of the HRAP components over those of the WSP due to their content in chlorophyll.
- On another hand, the agronomical experiments show that the most interesting result obtained on nitrogen leaching beyond the root zone is given by alfala. This crop is revealed as an excellent nitrogen exporter.
- Under normal conditions, alfalfa is a nitrogen fixing crop. This is achieved through the nodules heard by the roots. The amount of atmospheric nitrogen fixed should be added to the amount of nitrogen applied with the successive irrigations and therefore this will push the balance toward a positive figure indicating a nitrogen leaching beyond the root zone. Under our conditions, however, no nodules were formed on the roots. This is why our balance is negative demonstrating the powerful nitrogen uptake by alfalfa that helps in controlling nitrogen leaching beyond the root zone.
- We do not have any explanations for the absence of the nodules on the roots at Ouarzazate. Probably this is due to an inhibition effect exerted by the nitrogen content of the large amount of mineral nitrogen occurring in the experimental soil or/and by an inhibitory effect of the saline conditions that prevail in the area of Ouarzazate.
Malta
- The ultimate purpose of Malta's contribution to this project is to provide data on which a more ecologically sound strategy will be available for wastewater treatment and reuse. At present, the major source of chlorination DBP that may reach the marine environment in Malta is the cooling of thermal power stations using seawater. However, a five-fold increase in the production of treated wastewaters is being planned for the next five years. Such treated wastewaters that may be produced in excess of that required for reuse in agriculture and industry, will be chlorinated and probably discharged into the sea. This will then be the most significant source of chlorination DBP in the marine environment.
- In the first stage of our investigations, the biological impact of discharge of untreated sewage through the major sewage outfall in Malta, was assessed through a number of field studies, through the use of satellite remote sensing of the area, and through field monitoring of biomarker of strees in fish collected in the same locality. Such data indicates that this biological impact is highly significant and that sewage treatment is highly desirable.
- The efficiency of such treatment plants may however be jeopardised by pollutants (i.e. in industrial effluents) in the receiving wastewaters. This was in fact proved through a simple experimental protocol that was purposely developed. This test measures the reduction in nitrification efficiency of such plants on exposure to industrial effluents. Effluents from local tannery and metal industries may be expected to negatively affect the efficiency of such sewage treatment plants.
- A number of laboratory based ecotoxicological tests were carried out to assess biological impact of bromoform and chloroform (major DBP in marine environment) on selected marine organisms. These included acute toxicity tests on adult marine snails; on embryo and young larval stages of a sea urchin; as well as on the behavioural and physiological responses of snails and bivalves to these DBP. All these experiments indicate that populations of certain species are at risk when exposure to the levels of chlorination DBP to be encountered in the field as a result of chlorination sources as identified above.
Spain
- Production of olive oil inevitably leads to the creation of highly polluting effluents. The problem of this waste has become critical over the last few years in many Mediterranean countries. In this context, experiments have been carried out to reduce the chemical oxygen demand (COD) using several purification systems that may easily be applied, especially on a small scale.
- It was decided to use a methodological approach divided into two principal phases :
- treatment with the Aspergilus niger (ATCC 10864) fungus;
- subsequent biological treatment with aerobic micro-organisms from the washings of the discharge.
- We have noted an active purifying effect on effluents, both with Aspergilus niger and Aerobic bacteria from washings of the discharge. COD has been reduced by 50%. However, it appears that the effect of the Aerobic bacteria on effluents already treated with Aspergilus niger is additive and cumulative reduction of 75% can be achieved.
The research methodology is based on parallel investigations of various aspects related to wastewater treatment, to agricultural reuse and to human health care. In particular :
- Engineering and sanitary of advanced disinfection. Comparison of different disinfection technologies (i.e. ozone, chlorination, hydroge peroxide, ultraviolet, rays, silver and other heavy metal ions) in terms of germicidal effect as well as formation of harmful by-products formation will be made at pilot and/or full scale level;
- Low-cost technology wastewater treatment systems. Low-cost technology systems of wastewater treatment for agricultural reuse appropriate to Mediterranean countries such as high rate algal ponds that accounts also for heavy metals content of wastewater will be evaluated at pilot and field level. An optimisation of schemes for wastewater utilisation in agriculture by reference to crops, penology, groundwater vulnerability, irrigation methods and organisational aspects will be assessed;
- Environmental impacts on sea and ground water. Reduction of rates of nitrification in secondary treatment as result of exposure to heavy metals will be measured as a means to evaluate the epidemiological and toxic effects on aquatic life and deep groundwater of partially disinfected wastewater;
- Investigation of health implications and waterborne diseases. Appropriate methodologies for measuring the diffusion of waterborne diseases and related pathogens in wastewater and detecting endemic Mediterranean species and selected DBP and listed chemicals in food will be assessed.
Topic(s)
Data not availableCall for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
70121 Bari
Italy