Emerging Contaminants like Prescription and non-prescription drugs, Home care products, Veterinary and human antibiotics, Industrial and household products, Sex and steroidal hormones, Other endocrine disrupters
Dear Fidelis,
The group of pharmaceuticals and personal products (PPPs) has received much attention recently. PPPs include a very wide variety of products including drugs that require a prescription or not, veterinary drugs, nutritional supplements, perfumes, cosmetics, deodorants, soap, sunscreen and other products consumed by humans for personal or cosmetic purposes.
A typical municipal water treatment plant will use the process of coagulation, flocculation, sedimentation, filtration and disinfection with chlorine. PPPs can not be removed by the process of coagulation and filtration. Several types of PPPs may be destroyed by the chlorine but many remain unchanged by chlorine. There is evidence to show that ozonation may be effective to create the oxidation of PPPs that can form non-toxic substances. Nanofiltration, ultrafiltration and powdered activated carbon are also processes that were able to successfully remove the PPPs. However, in typical municipal water treatment plants, there are few facilities that use these processes to treat drinking water.
Depending on the level of treatment that wastewater receives only a few facilities can completely treat certain contaminants. For example, a level of secondary treatment can remove 95% of synthetic estrogen but not all wastewater treatment facilities that are equipped for secondary treatment.
Most PPPs are not destroyed in the water treatment process waste. Even the secondary and tertiary treatment is not able to remove the PPPs.
The triclorarbon is an ingredient of antibacterial soap and can be highly toxic when ingested. Scientists have estimated that the waste water treatment equipment can only remove 25% of triclocarbon in water.
With my best regards
Prof. Bachir ACHOUR
Dear Fidelis,
The group of pharmaceuticals and personal products (PPPs) has received much attention recently. PPPs include a very wide variety of products including drugs that require a prescription or not, veterinary drugs, nutritional supplements, perfumes, cosmetics, deodorants, soap, sunscreen and other products consumed by humans for personal or cosmetic purposes.
A typical municipal water treatment plant will use the process of coagulation, flocculation, sedimentation, filtration and disinfection with chlorine. PPPs can not be removed by the process of coagulation and filtration. Several types of PPPs may be destroyed by the chlorine but many remain unchanged by chlorine. There is evidence to show that ozonation may be effective to create the oxidation of PPPs that can form non-toxic substances. Nanofiltration, ultrafiltration and powdered activated carbon are also processes that were able to successfully remove the PPPs. However, in typical municipal water treatment plants, there are few facilities that use these processes to treat drinking water.
Depending on the level of treatment that wastewater receives only a few facilities can completely treat certain contaminants. For example, a level of secondary treatment can remove 95% of synthetic estrogen but not all wastewater treatment facilities that are equipped for secondary treatment.
Most PPPs are not destroyed in the water treatment process waste. Even the secondary and tertiary treatment is not able to remove the PPPs.
The triclorarbon is an ingredient of antibacterial soap and can be highly toxic when ingested. Scientists have estimated that the waste water treatment equipment can only remove 25% of triclocarbon in water.
With my best regards
Prof. Bachir ACHOUR
In practice this is only being done on a larger scale by the Schweitz and they have just started to upgrade their plants. They use two concepts: Ozonation or sorption on powder activated carbon, both as upgrades to existing tertiary biological-chemical treatment plants.
In sewage treatment plants the main processes that remove emergent contaminants are biodegradation and sorption to sludge. Biodegradation is the most important, but also the most variable as biological treatment can be made in different configurations. Generally the more intense and longer treatment aiming to achieve N and P removal achieves better removal of emergent contaminants than plants that only remove biological oxygen demand or nitrifies the wastewater. Sorption is important for fewer emergent pollutants and it varies less between types of treatment plants.
Some plants use large polishing lagoons and in these plants many pharmaceuticals that are not removed in the biological treatment are photolysed.
Several research groups are investigating if the biological treatment can remove even more micropollutants than the best nutrient removal wastewater treatment plants, by replacing activated sludge with suspended biofilm (MBBR) which seems to have capacity to biodegrade more chemicals.
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Dear Fidelis
The removal of emerging organic contaminants has complicated wastewater treatment, since conventional waste water treatment plants (WWTPs) are not designed for this purpose. Moreover, a typical WWTP is dimensioned on an average wastewater load (amount of sewage and contents in the sewage), which means that in case of intensive and/or long-term rainfall, the plant doesn’t have enough capacity (Sludge Retention Time-SRT) to maintain a sufficient purification at high supply of water. Therefore, the pollutedsewage water is directly drained on the natural surface water body (stream, river or lake) without cleavage.
As Henrik Rasmus Andersen commented above, in the Swiss “Micropoll Strategy” project complementary treatment steps have been evaluated and it has been shown that water quality can be significantly improved using processes such as powdered activated carbon adsorption or ozonation. Also a further treatment by micro- or nanofiltration or reverse osmosis is possible for water reuse strategies. Within POSEIDON project, which was carried out within a European Framework, many relevant techniques and processes involved in the urban water cycle have been assessed regarding their removal efficiency. One of the technologies studied for the removal of organic contaminants is the Membrane Biological Reactor (MBR). However, compared to conventional WWT, membrane assisted biological WWT can only improve the elimination efficiency of pollutants but cannot stop entirely the discharge of mainly polar pollutants with the permeate. Moreover, the costs of building and operating a MBR is usually higher than those of a conventional wastewater treatment. Therefore the treatment process for elimination of recalcitrant pollutants can be optimized only by a modification of the membranes and/or by a modification of the treatment process.
In Poseidon, which ended more than a decade ago, it was indeed investigated how much Membrane Biological Reactor (MBR) could improve biodegradation. The generally theory behind this is that it has been observed that the ability to degrade organic micropollutants in conventional activated sludge (CAS) increases with higher sludge retention time (average age of biomass) and MBR can operate with higher sludge age than is practically possible in CAS. Additionally sludge flocs in in MBR are smaller than flocs in CAS, which gives a kinetic advantage for MBR.
Sadly, the conclusion is that biodegradation rates for organic micropollutants only improve slightly in MBR compared to CAS. As MBR use significantly more energy for aeration than conventional activated sludge (CAS) it is not a great advantage.
In my comment above I wrote about Moving Bed Biofilm Reactors (MBBR) in which activated sludge is replaced with suspended biofilm. MBBR has more or less the same energy consumption for aeration as CAS. In biofilms the sludge age is extremely high in the lower layers of the biofilm while it is short in the surface, thus there is a continiium of different sludge ages in the same tank that allows more different microorganisms to co-exist. Additionally biofilms in wastewater treatment have a greater redox stratification than is seen in CAs flocs. Altogether this appears to give a greater ability to degrade organic chemicals than is found in CAS.
http://technomaps.veoliawatertechnologies.com/minizoom?media=videos&objectId=39260&lang=en&src=kit_vwst
There are several methods for removal of organic contaminants from wastewater including adsorption, oxidation, microbiological, photocataylsis, etc. Please see these articles:
Journal of Hazardous Materials B138 (2006) 152–159
Journal of Molecular Catalysis A: Chemical334 (2011) 123–129
Journal of Hazardous Materials175 (2010) 992–1000
....etc.
It is not an easy task, due to very different substances
with very different chemistry. It will need a 4th step in plants, with a common oxidation method, perhaps in the surface of TiO2 nanoparticles with the help of light or UV irradiation.
TiO2 based photocatalysis is non-efficient and thus expensive to apply for large water streams such as municipal wastewater. For this reason it has never been used in full scale for any municipal water treatment.
The cost efficient treatments that are known are ozone and activated carbon.
Henrik: Ozone is well sujited for that work, bukt thje problem is that tropspheric ozone is carcinogenic. I think activated carbon retains only partially that type of contaminants..
Ozonation and application of activated carbon powder as treatments for micropollutants in wastewater have already been implemented in full scale WWTPs in Schweitz and Germany. Therefor there is no doubt that it is realistic and feasible.
Ozone systems for water treatment are designed to consume the ozone by reactions in the water. Any residual ozone from the contact tank is destroyed in an offgas treatment system.Thus water treatment doesn't add to the ozone in the troposphere.
Both treatments have weaknesses and miss certain types of organic chemicals then applied at economically realistic doses. Ozone is inefficient for polyhalogenated chemicals such as iodinated x-ray contrast media while activated carbon absorbs poorly small highly polar chemicals.
https://en.wikipedia.org/wiki/Tropospheric_ozone
Ozone water treatment has been approved by the US EPA and is broad application for both municipal and industrial water. As Dr. Andersen observed, ground level ozone (tropospheric) is not going to be significantly increased by water treatment versus products of reaction from typical sources esp. transportation emissions. In any case , tropospheric ozone is not typically associated with carcinogenicity https://www.epa.gov/ground-level-ozone-pollution/health-effects-ozone-pollution. Activated charcoal adds significant maintenance, material and capital costs.https://www.epa.gov/dwregdev/drinking-water-treatment-technology-unit-cost-models-and-overview-technologies
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