With a few seconds reflection, it should be immediately obvious that the dyes used to make, among other things, our clothing, are designed to be persistent molecules - resistant to fading by light, resistant biological degradation, resistant to many chemical treatments, including treatments by laundry detergents.
Let me tell you something: Anything that resists change - and this of course would include political conservatives although that is not the meaning here - is a potential environmental problem.
As it happens - although people don't think about it - laundry detergents themselves can be persistent compounds - and anyone who has observed soap suds forming in flowing streams and rivers ought to have their thinking on this subject stimulated.
This brief diary, derived from my interest in waste water treatment, may be thought of as a second in a series of a diary I wrote over a year ago, A Brief Overview Of Persistent Halogenated Pollutants: The Case For Solvated Electrons.
I will be citing four papers from the primary scientific literature here. They are:
- "Determination of photodegradation and ozonation by products of linear alkylbenzene sulfonates by liquid chromatography and ion chromatography under controlled laboratory experiments" Talanta 64 (2004) 69–79
- "Irradiation treatment of azo dye containing wastewater: An overview," Radiation Physics and Chemistry 77 (2008) 225–244
- "Radiolytic decomposition of multi-class surfactants and their biotransformation products in sewage treatment plant effluents" Chemosphere 66 (2007) 114–122
- Trends in Analytical Chemistry, Vol. 26, No. 2, 2007, 116-124
The authors of these papers come from three countries and can be accessed by clicking on the links. They are Spanish, Columbian, and Hungarian scientists.
From the Talanta paper, we can get some idea on the scale of this problem in the case of laundry detergents. To wit:
Linear alkylbenzene sulfonates (LAS) are currently discharged after use into waste waters and can reach surface waters and coastal sea waters [1]. According to recent statistical data LAS comprises about 50% of all used anionic surfactants. In 1995, the world production of LAS was ca. 2.8×10^6 [2.8 million] tonnes but now more than 4×10^6 [4 million] tonnes are consumed globally every year. LAS remains as the lowest-cost surfactant and its use is still dramatically increasing in developing countries such as China [3]. Commercial LAS mixtures were introduced in the mid 1960s consisting basically of five homologues from C10LAS to C14LAS, each one containing several phenyl positional isomers (26 in total: internal and external) Besides it, 3–8% DATs (dialkyl tetralin sulfonates, see Fig. 1c) and 3–6% iso-LAS (isomers with a methyl group branched to the linear aliphatic chain) may also be present in such a mix. These linear compounds, unlike to branched ones, are usually classified as biodegradable, although several studies showed that biodegradation of C12LAS, or DBS (dodecyl benzene sulfonate) is rather slow and inefficient [4,5].
One thing you need to know about these compounds is that they are designed to be cheap and as such are mixtures, not pure compounds. As mixtures, their chemistry is not clear cut and the biology of one component may not be equivalent to the biology of the others. The detergent business is very much geared to low cost. I was once involved in a negotiation about an enzyme inhibitor for detergents - and yes detergents do contain enzymes - it's not all marketing hype - and I determined that the inhibitor at the price we were proposing would add just 0.02 cents per box of detergent. This was deemed way too expensive.
These types of surfactants, by the way, were invented for environmental reasons. The predecessor surfactants were alkyl phosphonates which were readily biodegradable. However their biodegradation released phosphorous, which in turn, fertilized the rapid growth of algae in ponds and lakes, algae which choked off the oxygen supply in the waters, causing the death of fish and other species. This sort of thing is called eutrophication, and it is the cause of biological death of huge stretches of the Gulf of Mexico near the mouth of Mississippi River owing to the (phosphorous) run off connected with fertilizers for Midwestern agricultural fields.
The Trends paper gives a nice overview of concerns relating to some of this compounds, and present practice involving the use of sewage sludge as fertilizer, something by the way, despite a clear level of risk, I generally support as an outgrowth of my concern about global phosphate flows.
After use, they are discarded down the drain into municipal sewer systems and afterwards treated in wastewater-treatment plants (WWTPs), where they are completely or partially removed by a combination of sorption and biodegradation. The biodegradation of surfactants in WWTPs has been studied in numerous papers. In general, most of the surfactants are well eliminated by conventional wastewater treatment, but some surfactants have a low biodegradability of the parent compounds, and, in others, undesirable biodegradation products are formed and discharged with WWTP effluents into surface waters. APEOs are examples.
Although they are not classified as highly toxic compounds, their metabolites (alkylphenols (APs) and alkylphenoxy carboxylates (APECs)), formed by the degradation of parent compounds generated during wastewater treatment, have proved able to mimic endogenous hormone 17b-estradiol [2]. Sewage sludge provides another potential route for introducing surfactants and their metabolites into the environment. If sludge is used as fertilizer in agriculture, surfactants can reach the soils, where they are possibly further degraded or transported into groundwater andsurface water.
The Trends paper does however, make a point that is often overlooked, which is that sometimes the detection of potentially problematic compounds is not really the function of something new, but is rather than a function of improved analytical techniques. For those who may be familiar with concepts in analytical chemistry, the LC/MS/MS systems described in these papers include ion traps as well as MALDI-TOF systems.
Science of the Total Environment is a wonderful journal to read and makes one wish that one had infinite time. This paper is a bit to jargonized for my taste, with too many abbreviations "EDC" for "Endocrine Disrupting Compounds" and "VAP" for "value added products" and
"WWS" for wastewater sludge...etc...etc.
Nonetheless it obviously also refers to the estrogen mimetic problem associated with a variety of surfactants.
It also does a nice job of describing the benefits and pitfalls of approaches that underlie all of my personal approaches to dealing with so called "waste" problems, which is to approach all so called "waste" from the standpoint of viewing it as a raw material for some useful system.
The history of using sewage sludge and recovered sewage water - which is actually cheaper to process than desalination - for irrigation and even for municipal water supplies is long and well explored, and in some cities, even industrial. (I note that the cooling water at the Palo Verde Nuclear Plant in Arizona is recovered sewage water.) But there are risks and problems associated with these approaches.
Furthermore, recently, wastewater sludge (WWS) has been subjected to reuse for production of value-added products (VAPs) through the route of bioconversion. Bioconversion of WWS into VAPs (biopesticides or other bio-control agents, microbial inoculants, industrial enzymes, bacterial bioplastics and other biopolymers) has been achieved with successful and encouraging results (Ben Rebah et al., 2001a, b, 2002a,b,c; Lachhab et al., 2001; Montiel et al., 2001; Tyagi et al., 2002; Vidyarthi et al., 2002; Brar et al., 2004, 2005a,b, 2006a,b, 2007, 2008, in press; Barnabé et al., 2005; Verma et al., 2005, 2007a,b; Yezza et al., 2005; Yan et al., 2006). Production strategies were developed to enhance product yield as for example the increase of WWS biodegradability through pre-treatment (Barnabé et al., 2005). VAPs as biopesticide and microbial inoculants will be field applied after preparing formulations from fermented WWS. Apart from the use of WWS as a raw material to replace synthetically used raw material to produce VAPs, WWS possesses other interesting inherent characteristics (Ben Rebah et al., 2001b; Brar et al., 2004, 2006a,b) example, a) suspended solids acting as ultraviolet light shield for insecticidal proteinaceous toxins; b) buffering action; c) presence of extracellular polymeric substances; d) presence of UV absorbing chromopheric units that reduce the need for additives in formulations and preserve or improve the functionalities of the microbial derivatives.
Besides the listed stuff here there are many other potential uses for waste water sludge. I personally sometimes feel as if I am bursting with ideas on this front.
But one of the most serious issues facing humanity is the problem of phosphorous. Phosphorous is an absolutely essential element for all living things, and the biochemistry of phosphorous is critical to metabolism as well as, famously, genetics, and (maybe less famously) to operations of all proteins - the most important enzymes in the world are kinases which phosphorylate serine, threonine and tyrosine residues in other proteins. Indeed phosphorylation is critical to cellular energy, and plays critical roles in photosynthesis as well as in the conversion of sugars into energy in glycolysis and the famous "Krebs" cycle. Indeed the energy "currency" of all cells are the phosphorous compounds ADP and ATP, respectively a diphosphate and triphosphate.
Noted in the paper:
From a commercial point of view, WWS rich in carbon, nitrogen and phosphorus and micronutrients could be a very interesting raw material for industrial fermentation. Cultivation of industrial strains in WWS using conventional industrial fermentation procedures (media sterilization, inoculum production, monoculture, fedbatch culture...) have been explored by many authors...
...These studies showed that many cmmercial products (bioinsecticides or other biocontrol agents, microbial inoculants for fertilization of leguminous cultures or industrial enzymes as bleaching agents, etc.) are promising VAPs that can be obtained from fermentation of raw or pretreated WWS. Sludges are low cost (even negative) raw materials and reduce sometimes the need for numerous additives for formulation of the commercial product (Brar et al., 2006a,b, 2007). WWS based VAPs are low cost products that can compete with toxic or less expensive chemicals or other costly biological alternatives. The advantages associated with this approach are: (i) sludge volume reduction; (ii) substitution of fresh biomass by WWS for commercial microbial derivatives production; (iii) replacement of chemicals in many applications and hence lower release of toxic chemicals breakdown products into the environment (for example, replacing chemical plastics via bioplastics and thus reducing the load of plasticizers into the environment); (iv) sequestration of carbon into microbial cells or derivatives instead of loosing it through WWS digestion (as CO2 and CH4)...
But anyway, I was suppose to say something about solvated electrons in this diary, so let's now turn to the Radiation Physics and Chemistry paper which discusses dyes which, as mentioned above are designed to be persistent chemicals.
(The chemistry of dyes, by the way, was one of the prime driving forces for the creation of the chemical industry based on aniline dyes.)
The authors offer what I have repeated above:
Azo dyes are frequently used for dyeing fabric therefore they are expected to be adherent, long lasting, and resistant to sunshine and chemical processes, in the case of dyed fabric it is required that the dyes should not fade through oxidation in the normal washing process. However, it is of special importance that these dyes could be removed from industrial effluents. For this purpose, either sorption (Aksu, 2005; Solpan and Ko¨ lge, 2006) or degradation, e.g., by treating with one-electron oxidants have been employed. In the so-called advanced oxidation processes (AOP) for the degradation of organic pollutants, highly reactive species, mainly hydroxyl radicals are used as primary oxidants.
Radiation treatment belongs to the class of AOP. Radiation processing is extensively used in industry to produce a wide range of products. Use of radiolysis in the environmental remediation of wastewater, contaminated soil and sediment is a promising treatment technology; the chemistry behind these technologies is under extensive investigation. Together with the removal of target chemical contaminant, one should also concern the elimination of a series of intermediates of progressively higher oxygen-to-carbon ratios that are involved in the conversion of an organic molecule to CO2. Therefore, it is essential to improve substantially our basic understanding of the radiation chemistry of dyes (reactions, pathways, and rates) in various systems. The purpose of this work is to make a review on the results obtained both at our laboratory and at other laboratories on the degradation of azo dyes with special emphasizes on radiation degradation of H-acid containing azo dyes.
This is a matter of solvated electrons, this AOP business.
Actually, there's nothing particularly new about the specifrics of the idea of using radiation to detoxify water and many approaches to this problem are well understood.
In the 1950's, if you look (and I have), there were many proposals and investigations of using so called "nuclear waste" for the purpose of irradiating sewage sludges and grey water for the purpose of detoxifying them. Mostly they were good proposals although in the later case, there were some drawbacks concerning, ironically enough, given that the irradiation targets here, the dyes, are "azo compounds" which are close organic analogues of nitrogen gas. Actually the chemistry of nitrogen is very complex, probably only second to its neighbor in the periodic table, carbon. Many nitrogen compounds are suspected or known carcinogens, for instance the nitrosoamines that are widely found in cooked meat and other cooked foods. The irradiation of grey water was known to produce some of these compounds, although the problem is clearly surrmountable on a little reflection. But the major drawback in the 1950s was simply that there was not enough nuclear material to go around to manage the industrial scale, and, of course, that the handling of radioactive materials was still in its infancy.
Also there was only a tiny commercial nuclear industry, much over shadowed by the (then) larger weapons industry. This placed physical constraints on the amount of such material that was available. As I have pointed out in previous diaries here, fission products are the only by products that possess maxima on their accumulation, dictated by the Bateman equations, meaning that they are dominated by equilibria. Eventually they will always be essentially decaying as fast as they are being formed more or less.
By the late 1960's and escalating in the 1970's and 1980's, the world was dominated mostly by radiation paranoia, albeit of an irrational type, and the potential for these sort of approaches were shelved.
However the situation is very different today, and correspondingly, the scale of our water emergency is vastly greater than it is today.
I have thought quite a bit about this problem, and it seems to me that this is an excellent place to apply radiation chemistry, but I'm not running things.
I do not expect, by the way, that these things will be applied or appreciated, but, it seems to me, in a rational world, they would be appreciated.