Talk:Sewage treatment

Environmental impact
From "Sewage treatment in developing countries" (http://en.wikipedia.org/wiki/Sewage_treatment#Sewage_treatment_in_developing_countries): "'Developing countries as diverse as Egypt, Algeria, China or Colombia have invested substantial sums in wastewater treatment without achieving a significant impact in terms of environmental improvement. Even if wastewater treatment plants are not properly operated, it can be argued that the environmental impact is limited in cases where the assimilative capacity of the receiving waters (ocean with strong currents or large rivers) is high, as it is often the case.'" This paragraph is highly questionable and I am going to remove those lines until somebody finds a reliable source to proof this statement. —Preceding unsigned comment added by 141.65.4.56 (talk) 13:03, 16 March 2010 (UTC)


 * Agreed. This argument is typically based upon statistical comparison of traditional physical-chemical analyses including biochemical oxygen demand, total suspended solids, turbidity, and dissolved oxygen.  There are at least two other broad categories to be considered.  The first is bacterial and viral pathogens.  Water quality has traditionally been assessed with coliform counts, but coliform organisms live in such a wide variety of hosts that high background levels from birds, rodents, and domestic livestock and pets may mask true sewage plumes.  Measurement of true pathogen counts is comparatively seldom undertaken, and assumptions of coincidence with receiving water coliform counts are questionable.  Another emerging issue is the significance of enzymatically active substances capable of causing biological changes at unmeasurably low concentrations.  These situations were first identified with industrial wastes like polychlorinated dibenzodioxins (potentially present in bleached toilet paper), but can also result from hormones or pharmaceutical drug residues in human urine and feces.  Estrogen levels from oral contraceptives or menopause therapy may be high enough to impede sexual development of fish, amphibians, crustaceans, or insects maturing in receiving waters.Thewellman (talk) 20:07, 16 March 2010 (UTC)

Process Sequence
I've noticed that the sequence in which each part of the sewage works process is in a specific sequence, as if it were saying "this is the order in which the seperate processes occur", but this is in fact incorrect as each plant arranges their process in a slightly different way, with slightly different methods employed at each stage. There are so many different ways of arranging plants, each with their own benefits and reasons, that it seems incomplete without at least mentioning this and going into some detail on it.

I propose that, rather than going through the process step by step (which is going to be incorrect the second you start looking at a different plant, as the author seems to've taken his information from one specific plant in Wales), processes used on most sites should be described individually, each with a little footnote on what part of the whole treatment process it's usually used in, to give the reader a general overall understanding of the methods employed and the common application of those methods.

At the end of the article, with the reader now fully knowledgeable of what components can make up a sewage treatment plant, there can be an expansion on the structuring and arrangement of components of a sewage works, and their relative merits. There seems to be a lot of potential knowledge to be shared on what factors into decisions on how sewage works are structured. If this is not possible, then at least a few of the most common arrangements, and then a description of the variables that determine what methods are used where would be desireable. There are so few constants in the world of sewage treatment, that it would be impossible to structure one article around a "typical" sewage works, because such a sewage works does not exist.--Badharlick 17:10, 10 April 2006 (UTC)

Since I appear to be the contributor from Wales,I can confirm that this is not experience from Wales but across the world including the USA, New Zealand, Australia and several countries in Europe (France, Spain, Italy, Greece etc.) including a great deal of work around London including the two big works serving London. Wherever you go, the principles are the same, settle the solids out, treat the resulting liquor, settle out the biological solids and get rid of the water to the environment and the solids somewhere else. You can join these processes up in all sorts of novel and interesting ways but the principles usually stay much the same. Velela 21:27, 10 April 2006 (UTC)


 * I did respond but Wikipedia obliterated my response. I tried to say that, you make exactly my point. There are many sorts of novel and INTERESTING ways - please give me a reason why these shouldn't be added to the article? I'm not critising the work that you've done, more the work that hasn't been done. There's lots and lots of information that can be added here, and just because you "don't think it's important for the public to know" doesn't mean it shouldn't be added. There's whole processes, equipment, methods, equipment names, and various other things that aren't listed in the article that are actually really quite important if you're even semiserious about the subject. What about hydroseperators? Different types of hydroseperators for different purposes? The difference between a settling tank and a hydroseperator and their relative merits? Different types of drying equipment? --Badharlick 19:35, 13 April 2006 (UTC)

Structure
I added little bit on historical section, but it is far from being enough.
 * Historical section is still too limiting.
 * "Modern sewage treatment" is mixed with laws, problems, and systems for sewage treatments. It should be splitted into different sections.
 * This can mention how sewage are treated inside factories, which is mostly due to regulations.
 * The incineration of sewage can be quite safe as long as the industrial waste water that causes most problems is separated.

Revth 09:55, 23 Sep 2004 (UTC)

Its only been relatively recently that sewage has actually been treated rather than just removed and dumped in the nearest river...sewers already has quite abit about the collection of sewerage, and would seem to me to be the best place for long histories on sewer systems etc. Iain 10:44, 23 Sep 2004 (UTC)

This still seems confusing with sewerage (the pipes and pumps etc.) and sewage treatment mixed in one article. It looks as though we should separate out the sewerage bit ( and this would include most if not all the history) into sewers as Iain suggests. It would also be cleaner if the administrative and regulatory aspects could also live elsewhere. I hope that the current version is closer to what Bantman had in mind ?

Velela 12:24, 26 Nov 2004 (UTC)

I think this article needs cleanup, more interWiki links, and a native English speaker should proof read it. 213.51.209.230 18:48, 26 Nov 2004 (UTC)

Untreated sewage disposal

 * In many other countries, including many quite-wealthy ones, untreated sewage is released directly to surface water.

Which wealthy countries release untreated sewage to surface water? Burschik 10:00, 23 Sep 2004 (UTC)


 * Stupid ones? --ZayZayEM 04:44, 9 Nov 2004 (UTC)

In the urban UK, excess sewage can be released to surface waters during storm events. There are certainly plenty of examples of poorly teated sewage visibly imapcting upon the reciving environment in wealthy countries. If visible signs are present (anoxic zones, presence of Sphaerotilus spp ("Sewage fungus"), absence of clean water indicator species and large numbers of facultative anaerobic species) it certain that there is unseen damage extending over wider areas. I have seen such conditions at locations in Western Australia, Queensland,, Greece, France and Spain and I am certain that most developed countries have their own examples. Velela 20:36, 23 Nov 2004 (UTC)
 * Brussels didn't have a WWTP until 2001; ironic given the importance of EU legislation in driving forward WWT in Europe... Rd232 15:58, 5 Jan 2005 (UTC)


 * i belive its accepted wisdom that its better to dump raw sewage into rivers etc than to let it back up in the pipes causing all manor of problems. So when treatment fails thats what happens! Plugwash 00:17, 14 March 2006 (UTC)

Treatment
Primary, secondary, and tertiary treatment all have time-tested definitions in the United States. I'm not an expert on this specific topic per se but do work in the industry, and would like to see the definitions conform more to current standards and practices. I can work on this if nobody else is willing to, but like I said, I don't run a treatment plant or anything....

I have provided some updates to treament methods but it is still North American flavoured. Much remains to be done and I an unhappy about some of the statements about the lack of environmental impacts for sewage discaring into high dilution systems. All the evidence demoinstrates that the impacts can be severe. Velela 18:34, 23 Nov 2004 (UTC)

Let's do this -- there should be a section describing standard treatment protocols in developed countries, a subsection pointing out international differences (say, between US, UK, europe, australian treatment methods), and another section entirely dealing with the environmental impact of variously treated (or untreated) wastewater. Bantman 18:48, 23 Nov 2004 (UTC)

constructed wetlands question
I'm working on an article about constructed wetlands; one primary use for them is wastewater and sewage treatment. I've linked back here, but I'm not sure how much detail I should go into on how they function as wastewater treatment systems. At the moment, I'm working on a description of their design for different purposes and plan to provide examples. Any suggestions? Deirdre 00:52, 9 Dec 2004 (UTC)

There is certainly a need for a reference here but I would suggest putting most of the detail in your existing constructed wetland topic. In the UK such wetlands include engineered reed-beds which are also widely used to treat agricultural waste and to help mitigate the effects of diffuse agricultural pollutionm, mine leachatres and highway run-off. Velela 16:07, 9 Dec 2004 (UTC)

Right-o. Will do.Deirdre 22:17, 9 Dec 2004 (UTC)

sewerage
Is 'Sewerage' not a more appropriate title for any article on sewers, pumps, etc? In my experience, the word 'sewers' refers exclusively to pipes, and not the other components of sewerage such as pumping stations. Sewer could then be used to refer to sewage pipe history/technology/usage which is a significant field in its own right, while sewerage could describe or link to sewage pumps, pumping stations, and network design. I would be happy to contribute.

I agree that in British usage, sewerage refers to and includes all that infrastructure used to convey sewage from its origin to the point of disposal and therefore includes pipes, valves, pumps, screens etc. I would be happy to see this separated out and included in a linked articlee provided that there is a similar usage in other English speaking countries. Does the word 'sewerage' have the same meaning in the USA and Canada ? I believe that it does in Australia and NZ. Velela 14:23, 18 Dec 2004 (UTC)

Unfortunately my personal experience is limited to the UK and Aus. Doing a quick google search seems to indicate that the term 'sewer system' is used in the US alongside 'sewerage' which might account for the confusion. The american Columbia Encyclopedia seem to concur with the UK/Aus definition. cphi, 20 Dec.

Restructuring of this article
The general structure of the topic within Wikipedia needs clarifying; my moving the bulk of the technical details of conventional wastewater treatment to its own article was intended as a start. I suggest


 * Sewerage should be the main article for the Sewerage topic. It would summarise and link to the appropriate articles for sewers, wastewater treatment and water industry; cover history (focussing on the broader aspects, not so much technical development, which would go into daughter articles); and the crucial public health significance of the whole thing.
 * Wastewater treatment should be the main article for treatment aspects, covering both greywater and blackwater (sewage), as well as stormwater; the technical details of conventional wastewater treatment shouldn't be allowed to overwhelm the entire article, so a daughter article plus summary is appropriate. This would also be the place to put (in a daughter article if enough detail) discussion of the environmental aspects of (lack of) WWT, being a key driver as well as health issues for its development.
 * Water industry should be the main article for the regulatory/business/organisational aspects of the water and sewerage industry. (Possibly it should be renamed appropriately; but "water industry" often is used to cover both.) We could have Sewerage industry but that would involve much duplication, so I'd leave that as an option for the future if it turns out to be necessary.

Comments? Rd232 14:38, 1 Jan 2005 (UTC)

I agree that this article needs to be divided into a number of separate topics and, as I noted before, I would certainly like to see the Sewerage part separated off as a priority. My problem was in finding a title that reflected widespread usage across the English speaking world - Sewerage seesm to be a UK relevant term not widely understood in USA. Maybe we just need to put a redirect in to manage this.

I also agree that the admin/ regulatory parts needs its own article but, to reflect a wide spectrum of practices throughout the world, perhaps this shoud be Sewage treatment industry or something similar which is very similar to your Sewerage industry but perhaps better understood in USA.

My main worry was that the tile Sewage Treatment should be an article about how sewage is treated - i.e. conventional wastewater treament methods - with the history, administration etc in their own separate articles. So although that I agree with most of what you propose, it was the very part that I would have wished to retain that was separated out first - hence my angst! Velela 09:51, 2 Jan 2005 (UTC)


 * I see your point. I couldn't see the wood for the trees with all the conventional wastewater tech detail...
 * I hadn't realised "sewerage" was UK-centric, but it does seem to be. So the umbrella term should probably be "wastewater" (or "wastewater system" or possibly "sanitation"), not least because "wastewater industry" is the preferred term for the industry. The category needs changing too, if we agree on this term. I would start off Wastewater industry as a redirect to Water industry as the latter often covers both, and it'll make it easier to develop the topic at this early stage since so many issues in common. Rd232 23:34, 2 Jan 2005 (UTC)
 * The distinction between sewers and sewage treatment is important - the issues and history are quite different. Rd232 23:38, 2 Jan 2005 (UTC)


 * That sounds fine. Do you want to have a go at it ? Happy to help but wouldn't want to get into editing conflicts which might be even more confusing !
 * Velela 10:56, 3 Jan 2005 (UTC)
 * Why don't you have a bash; I'm pretty busy for the next few weeks and the reworking will need more time and energy than I have at the moment. Rd232 15:54, 5 Jan 2005 (UTC)


 * OK - I have done the deed. Mostly just rather coarse cut and paste so probably a lot of loose ends to tie up and lots of wiki linking to fix. Help appreciated, comments welcomed.

Velela 17:58, 5 Jan 2005 (UTC)
 * Um. We haven't really settled the naming issue yet, have we? We need a main article, and a name for the category; currently the category is "sewerage", but sewerage just redirects to sewage treatment. I gather you're proposing "Sewage collection and disposal" as the main article but that doesn't seem right. I suggest wastewater industry, and the category be "wastewater". (Or else, given Wikipedia emphasis on common usage (groan), sewage industry and "sewage".) Similarly - for consistency and precision since sewage is a subcategory of wastewater - sewage treatment should be moved to wastewater treatment. Sewage - regulation and administration should be become part of wastewater industry. Comments? Rd232 14:23, 7 Jan 2005 (UTC)


 * I have delayed further editing because I am uncertain where this is going. I have expanded the Wastewater article to include examples of the types of wastewater.
 * I am not convinced that this article should be predicated on the 'wastewater industry or any similar title. Sewage is just one form of Wastewater. It is treated by the wastewater industry (whatever that may be from country to contry). It is also treated in communities, by private enterprise and by individual house-holders. Hence my reluctance to bundle this in with the waste water industry. I would be delighted to have an article Wastewater treament that had links to Sewage treatment, Organic waste treament, Toxic waste treatment etc (see Wastewater for a range of categories), but I do believe that Sewage treatment is a logical, self contained and appropriate article that should describe how sewage (and not wastewater ) is treated. I am happy to progress this if needed.
 * Velela 23:38, 16 Jan 2005 (UTC)

Well, perhaps the most correct title would be wastewater sector, though I would consider "industry" loosely a synonym for "sector" here. Either one would certainly include non-commercial WWT and conveyancing, and the widely differing forms in different countries, range of technologies etc - a real umbrella term... As you say, sewage is a subset of wastewater; and I strongly feel that there needs to be a single place to house an overview of the whole wastewater topic. We need something that straddles both WWT and sewer systems. Sewage treatment isn't the place, and we've established Sewerage isn't well-known enough (despite that currently being the Category); can we settle on wastewater sector? Or do you have an alternative suggestion? Some might suggest sanitation but I don't like that at all - it just feels too general. ...Anyway, I would point out that we can always change the name later. Rd232 07:23, 17 Jan 2005 (UTC)


 * In the US "wastewater treatment" is the most commonly used description among water professionals, although there is a move to using "water reclamation" as well as "water pollution control" when referring to facilities. The word "sewerage" is used to describe the infrastructure to a certain extent. "Wastewater" is probably used to describe used water more often than "sewage", at least in the business. Another term has come into use in the States because of the portion of the Clean Water Act and the resulting portions of the Code of Federal Regulations (CFR) regarding the responsibiilties of the Environmental Protection Agency (USEPA). The term is "Publicly Owned Treatment Works" abbreviated "POTW". It refers to both the Treatment faiclities and the wastewater collection system transporting wastewater to the treatment plant, and is very close in meaning to "sewerage" when restricted to a single system and is used most often in a regulatory context. - WCFrancis 17:40, 8 September 2005 (UTC)


 * This article is presently over 72K -- more than twice the 32K length considered a useful maximum for a compact table of contents allowing readers to quickly find the information they need, and editors to appropriately place their contributions. In the absence of objections, I propose to reduce this article length by about 10K by replacing the descriptive paragraphs and illustrations of the various methods of secondary treatment with this bulleted list of articles:
 * Activated sludge
 * Aerated lagoon
 * Aerobic granulation
 * Constructed wetland
 * Membrane bioreactor
 * Rotating biological contactor
 * Trickling filter
 * The broad description of secondary treatment would remain a part of this article; and much of the information to be removed from this article can be found by following the main article link to the secondary treatment article. I suggest access to information about other methods of secondary treatment can be through additions to this list if notability has warranted a separate Wikipedia article, or by description in the secondary treatment article if no separate Wikipedia article is available. Thewellman (talk) 18:56, 6 January 2015 (UTC)
 * Done. Thewellman (talk) 09:16, 12 January 2015 (UTC)

Formatting
Is there a nice way to clean up the "Lagooning", "Pressing", etc list? It doesn't read well, but since I can't even figure out if they're supposed to be subsections or separate sections, don't want to mess with it... --Bushytails 04:44, 24 Jan 2005 (UTC)

I have simplified the sludge treament and disposal sections to make tidier. However, the whole article still needs a major make-over see comments from Rd232 and others above. I will try and get round to this but it needs a clear head and some careful copy editing. Velela 13:52, 24 Jan 2005 (UTC)

Brand Names?
The article includes lists of "Possible Equipment" that I do not recognize. I have been a water professional for over 30 years and do try to keep up. I suspect that there may be brand names mixed in. I feel that an encyclopedia article should not include these in the main treatment article, although notable companies could have references and articles. For example, "belt press" and "vacuum filter" are types of dewatering equipment, but including Andritz or Roediger would be inappropriate since those are manufacturers. -- WCFrancis 17:39, 8 September 2005 (UTC)
 * I'm in the same boat since I've worked in the water and waste water treatment fields as well. A link to the articles on those devices which themselves contain a list of brands (inclusive, not just one or two but most or all manufacturers) would probably be more acceptable.  2601:1:9280:155:E1CA:5ABE:F2A2:BCEA (talk) 06:45, 15 April 2014 (UTC)

Use of Alum coagulants
I have reverted a new reference to the use of Alum coagulants in sedimentation. I am not aware of this practice, which sounds very expensive, especially as most sewage settles adequately without chemical assistance. If Alum is widely used, a reference would be useful and some idea of where in the world this is practiced (and also perhaps why ?). Velela 12:54, 3 January 2006 (UTC)


 * Alum is very widely used as a coagulant in potable water treatment, and used as well in waste water treatment plants where space is an issue. Indeed, it increases the sedimentation speed and thus reduces the size of the sedimentation tank, especially associated with a lamellar sedimentation tanks. Alum can always be used as well to cope with sedimentation problems. In that case, it's only a way to deal with badly designed plants.


 * But I do agree with you that this matter is a bit too specialized to be cited in this mainstream article. Kekel 09:19, 3 July 2006 (UTC)

Package plants and batch reactors
The following was deleted by User:206.128.209.28 on April 8th - not clear as to why:
 * For example, one process which combines secondary treatment and settlement is the Sequential Batch Reactor (SBR). Typically, activated sludge is mixed with raw incoming sewage and mixed and aerated. The resultant mixture is then allowed to settle producing a high quality effluent. The settled sludge is run off and re-aerated before a proportion is returned to the head of the works. SBR plants are now being deployed in many parts of the world including North Liberty, Iowa, and Llanasa, North Wales.


 * The disadvantage of such processes is that precise control of timing, mixing and aeration is required. This precision is usually achieved by computer controls linked to many sensors in the plant. Such a complex, fragile system is unsuited to places where such controls may be unreliable, or poorly maintained, or where the power supply may be intermittent.

posted: Paleorthid 16:15, 9 April 2006 (UTC)

I removed the "advertisement" notice. The content seems neutral enough to me. The mere fact that some sections will have more detail than others -- an unavoidable consequence of Wikipedia's method -- may result in some portions seeming laudatory or hortatory. Anyone who has knowledge of different treatment techniques that may be better, or who knows of drawbacks to the methods written of, is welcome to post such additional material.216.179.3.153 18:54, 24 July 2007 (UTC)

Thermal depolymerization
The following was deleted by User:206.128.209.28 on April 8th - not clear as to why:


 * Thermal depolymerization uses hydrous pyrolysis to convert reduced complex organics to oil. The premacerated, grit-reduced sludge is heated to 250C and compressed to 40 MPa. The hydrogen in the water inserts itself between chemical bonds in natural polymers such as fats, proteins and cellulose. The oxygen of the water combines with carbon, hydrogen and metals. The result is oil, light combustible gases such as methane, propane and butane, water with soluble salts, carbon dioxide, and a small residue of inert insoluble material that resembles powdered rock and char. All organisms and many organic toxins are destroyed. Inorganic salts such as nitrates and phosphates remain in the water after treatment at sufficiently high levels that further treatment is required.


 * The energy from decompressing the material is recovered, and the process heat and pressure is usually powered from the light combustible gases. The oil is usually treated further to make a refined useful light grade of oil, such as no. 2 diesel and no. 4 heating oil, and then sold.


 * The choice of a wastewater solid treatment method depends on the amount of solids generated and other site-specific conditions. However, in general, composting is most often applied to smaller-scale applications followed by aerobic digestion and then lastly anaerobic digestion for the larger-scale municipal applications.

Posted: Paleorthid 16:15, 9 April 2006 (UTC)


 * I couldn't see any reason for deletion so I have restored the missing text. Velela 08:22, 10 April 2006 (UTC)

I don't know if you know this, but treated sewage can be used as fertilizer. You all should look into it. It's a new form of making agriculture more productive.

Anaerobic Digestion
In addition to correct a mistake in the definition of "mesophilic" and "thermophilic", I deleted the reference to large tanks were sludge is supposed to be left for weeks in anaerobic conditions. I don't really understand what the original writer is talking about, as non-heated closed anaerobic digesters would have a huge, anti-economic, size and would only be possible were incoming sewage temperature would be high enough to allow this. Kekel 11:41, 29 June 2006 (UTC)

Wanna change the term "fermented" in the article. It is unapropriate, as fermentation product is alcohol. Thought about "hydrolysed", but it's not much better. Kekel 16:15, 9 July 2006 (UTC)


 * Fermentation is a part of anaerobic digestion, namely Mixed acid fermentation, as well as hydrolysis and methanogenesis. I dont mind using the term "fermented" since it's commonly understood, resonably correct and often used in non-technical literature to describe anaerobic digestion. Morphriz (talk) 09:34, 13 July 2010 (UTC)

Sewage sludge treatment
To try and make this article a more manageable size, I have created a new article as a home for the sludge treatment and disposal topics. I have retained a precis here as an overview but have tried to avoid overt duplication between the two articles. Velela 12:03, 5 July 2006 (UTC)


 * PLEASE have a look at the talk page for Sewage sludge treatment. I have added much as to the methods of dewatering and disposal, as that section is very small and needs to be expanded. i think right now that is the only topic on the discussion page. JAK83 17:41, 5 February 2007 (UTC)

Using catfish in septic tanks
(I posted this to Talk:Catfish, but it is also of relevance here.)

Catfish are used in septic tanks in Indonesia, to eat the waste and prevent the tank from filling up with solids too quickly. I can't find a valid source, so I'll just offer these links for now, and hope that someone comes up with a source. I might try and co-author a journal article on it next year, which would then be a valid source.

Blog post (and comments): Ikan lele technology

My comment: An Indonesian's comment on catfish in septic tanks

The Indonesian Wikipedia article on catfish mentions that freshwater catfish are used to remove impurities from water; it states that catfish used in the way must be cleansed before eating, by being placed in flowing water. (The article doesn't state how long for, or just how much this improves the taste & safety). --Singkong2005 &middot; talk 00:30, 31 October 2006 (UTC)

PHOTOS
I work at a 16MGD water reclamation facility, and would be happy to submit photos for the different processes, such as

-Influent Pumping -Screening (mechanical bar screens) -Degritting -Aereation basins (oxidation ditch) -Anerobic tanks -Anoxic tanks -Clarification (circular gravity clarifiers) -Tertiary Filters (Rapid Sand Filters) -UV Disinfection -Effluent Pumping -Sream Outfall -Laboratory -Aerobic Digesters -Various Equipment (pumps, blowers, motors, etc) -Power backup (turbo-diesel generators) -Sludge Dewatering (belt filter presses, centrifuge)

You want a picture of it I can get it. JAK83 18:31, 5 February 2007 (UTC)
 * Some additional images would greatly improve the article. Please go ahead. Only one caveat - most sewage in the world is actually treated in the many tens of thousands of small rural works so it would be good to maintain a balance and illustrate both large and small works Velela 21:39, 5 February 2007 (UTC)

Yes, I think you should submit photos as they would be very useful.And if you have the time please post take and post photos for all the processes


 * I think I will wait until Spring when there is no snow and the grass is green... not a great time now to take outdoor pics, but i will post some of the indoor processes here on the talk page. JAK83 03:56, 10 February 2007 (UTC)

JAK83 05:46, 15 May 2007 (UTC)

piometre?
The section on "Sedimentation solidification and evaporation" refers to a piometre. I can't find any information on what that is--could it be a typo? Ccrrccrr 01:41, 5 July 2007 (UTC)

a vandal made it I'll take it out. --Xiahou 01:50, 5 July 2007 (UTC) Was just about to say the same thing. Thanks for taking it out.--Mschiffler 01:54, 5 July 2007 (UTC)

UV Disinfection
here is layout of basic UV disinfection

Recycling water
In many countries strapped for water, it is necessary to recycle water from sewage treatment plants into either potable water, requiring high purity, or irrigation water, permitting a lower quality. I was rather surprised not to see either feature mentioned in this article, which is therefore incomplete. I don't have enough know-how to write a section, although I understand that single stage RO (much cheaper than desalination) plus UV irradiation is used for the former and ultrafiltration for the latter. Could anyone add this, please? --Devilinhell (talk) 07:30, 1 June 2008 (UTC)

Ive deleted Chemiviron's commercial website link... —Preceding unsigned comment added by 80.247.21.230 (talk) 08:05, 3 October 2008 (UTC) A major reason this is not practiced more widely in the USA for example, is that states have laws against reuse of water as you're somehow 'stealing' it from downstream users. Nevermind that you go and just take more of your quota from your reservoirs and dump your waste downstream in almost the exact same quantity. Or that most of that water you dumped never reaches the most downstream basin/reservoir in your state - it evaporates. Yes, this is (mostly) all due to the cattle wars. I'm not sure of the legality in other countries but this tends to be a true pattern, wherever water rights were literally fought over, which is practically everywhere. 2601:1:9280:155:E1CA:5ABE:F2A2:BCEA (talk) 06:53, 15 April 2014 (UTC)

PST's
A friend of mine that worked in water treatment always use to point out what he called Primary Settlement Tanks or PST's when we went past sewage works. As far as I can see there isn't a direct reference to them in this artical. Is that something that is missing? He was mainly refering to items like this:  62.189.100.228 (talk) 20:00, 5 February 2009 (UTC)


 * Yes, they are there. See Sewage treatment. Velela (talk) 20:12, 5 February 2009 (UTC)


 * Ah right, thanks. Is the acronym 'PST' in wide spread enough use to include it?  At the moment i don't see it. 81.158.252.81 (talk) 14:36, 8 February 2009 (UTC)
 * Never heard it used in the UK despite all my working life regulating sewage works. Possible it is used elsewhere. Velela (talk) 15:21, 8 February 2009 (UTC)
 * During 2007 - 2009 I have worked as a consultant engineer in London for water and wastewater treatment works. My clients were Thames Water, Anglian Water and Scottish Water and the acronym PSTs for Primary Settlement Tanks was commonly used. Silenzio76 (talk) 00:16, 3 May 2010 (UTC)

Fluidized bed reactors
I have removed the following text from the article because it seems to make little sense to me as part of the sewage treatment process. If someone can re-draft it so that it make sense to the ordinary reader and assuming that it is still relevant to this article, it could then be re-inserted.
 * The carbon absorption following biological treatment is particularly effective in reducing both the BOD and COD to low levels. A fluidized bed reactor is a combination of the most common stirred tank packed bed, continuous flow reactors. It is very important to chemical engineering because of its excellent heat and mass transfer characteristics. In a fluidized bed reactor, the substrate is passed upward through the immobilized enzyme bed at a high velocity to lift the particles. However the velocity must not be so high that the enzymes are swept away from the reactor entirely. This causes low mixing; these type of reactors are highly suitable for the exothermic reactions. It is most often applied in immobilized enzyme catalysis

Velela (talk) 11:20, 13 March 2009 (UTC)

Process Flow Diagram
I am a retired ChE with no sewage plant knowledge. I found the article a good introduction; however, I would suggest adding a specific discussion of the process flow diagram shown in the article. Its content does not relate directly to the text, resulting in unnecessary difficulty in understanding it. Ugodit (talk) 01:16, 22 February 2010 (UTC)

What happens to the non-organic soluble materials
Such as soaps, detergents, and other chemicals used in the laundry room, kitchen, and bathroom? —Preceding unsigned comment added by Consuelo D'Guiche (talk • contribs) 20:27, 18 May 2010 (UTC)
 * Soaps are organic, as are most detergents and other laundry products - nearly all or which are either chemically bound into fats and greases and skimmed of the primary tank or are degraded biologically in a filter bed or activated sludge tank. Truly inorganic materials such as washing soda, caustic soda (for those really tough stains!), bleach, chlorinated solvents react with other components or evaporate off during the aeration stage. Alkaline materials tend to saponify fats producing soaps and glycerine; chlorine from bleach mostly oxidises organic components producing innocuous chloride ion. However; some difficult or potentially toxic materials do remain including small concentrations of halogenated organics, pharmaceutical residues, hormone residues, medical radio-isotopes etc. all of which, very greatly diluted, are discharged into the environment.  Velela  Velela Talk 21:59, 18 May 2010 (UTC)

Settling chamber
Following edit has been removed; although the header "Circular sedimentation tanks" is best swapped for "Settling basin", I think it's accurate to place it at a seperate section. If you look at the schematic on the article, circular sedimentation tanks also come behind the rectangular, aerated/vortex basins. Hence, perhaps reinstate the infor by reverting to http://en.wikipedia.org/w/index.php?title=Sewage_treatment&oldid=472802720 91.182.211.156 (talk) 11:50, 26 January 2012 (UTC)
 * Circular sedimentation tanks, clarifiers, primary settlement tanks, secondary settlement tanks, sludge consolidation tanks - call them what you like, but they are probably the most common tank in the business and are mentioned throughout the article and therefore don't need a separate section as if they are something special or different.  Velella  Velella Talk 12:00, 26 January 2012 (UTC)
 * The choice between circular or rectangular tanks is largely a function of available space and volume of wastewater to be treated. Rectangular clarifiers are used where space restrictions or very large flows encourage common wall construction of multiple basins within a small land footprint.  Circular clarifiers may provide more efficient volume and flow characteristics where space is available.Thewellman (talk) 19:31, 26 January 2012 (UTC)

Process overview section
In the Process overview section, MBBR (Moving Bed Biofilm Reactor) is discussed in the Secondary treatment sub-section with a direct link to World Water Works’ website, a business that provides wastewater treatment solutions. With multiple businesses providing MBBR solutions such as Headworks Bio Inc, Veolia/ AnoxKaldnes and Siemens, is the direct linking of World Water Works’ website a Conflict of Interest? Specifically, a self-promotion? Perhaps linking to an industry trade group for an explanation of MBBR would be the better course of action? Water World, a nationally recognized industry trade group for wastewater treatment, provides a webcast on the topic of Evaluation, Application and Operation of IFAS and MBBR Technologies.


 * Almost certainly so. Please feel free to make an appropriate change.  Velella  Velella Talk 15:20, 27 April 2011 (UTC)


 * Done. Thank you for the confirmation.  I like to verify these types of issues via the talk page to ensure I am editing pages correctly.  EERichards  EERichards Talk  17:26, 27 April 2011 (UTC)

KVDP images - your knowledge would be welcomed.
The attention of those knowledgeable about water treatment would be welcomed at commons:Commons:Deletion_requests/File:Simple_water_treatment_plant.png

Thanks Andy Dingley (talk) 17:21, 31 January 2012 (UTC)

Energy use
Wastewater treatment currently consumes about 15 GW or about 3% of the electrical power produced in the United States. Domestic, industrial and animal wastewater together however contains about 17 GW of potential energy. At present, this energy is still untapped, yet could be extracted using a.

mention in article 109.130.149.22 (talk) 10:47, 5 January 2013 (UTC)
 * There's many, many possible ways to extract energy from organic waste.2601:1:9280:155:E1CA:5ABE:F2A2:BCEA (talk) 06:55, 15 April 2014 (UTC)

Nitrospira
Where is the reference on Nitrospira being more active than Nitrobacter in the environment? I have read that this is true only for marine environments. 122.3.43.60 (talk) 11:07, 19 March 2013 (UTC)

Origins of Sewage - more details needed?
"Communities that have urbanized in the mid-20th century or later generally have built separate systems for sewage (sanitary sewers) and stormwater, because precipitation causes widely varying flows, reducing sewage treatment plant efficiency. " This is one heck of an understatement. It does more than just reduce efficiency. It can totally disrupt a plant for a long period of time. It essentially shuts down many plant designs for various reasons, including the ecosystems in each tank. Maybe someone with more experience with this phenomenon could State it in more detail. It's not like it's even 'original research' since there's plenty of books to reference in the treatment industry on possible plant failures. For example, the books used to study for exams. 2601:1:9280:155:E1CA:5ABE:F2A2:BCEA (talk) 07:04, 15 April 2014 (UTC)

"Sewage treatment in developing countries" section
This sections seems like an indiscriminate collection of information. The thing that seemed wrong to me initially was the inclusion of Israel, which is a developed country, but actually the section is problematic overall. It mostly provides random information from three countries: Venezuela, Iran and Israel. There is one general and unsourced line about sub-Saharan Africa without any useful information. There is no information about Asia or the Americas beyond the above countries.

I see two possible solutions: either removing the section entirely, or having a by-country section which will list information on sewage treatment in as many countries as possible.

—Ynhockey (Talk) 15:19, 9 December 2014 (UTC)


 * I agree that this section needed more work. I have done a bit but it needs more. I have moved the part about Israel to a new section on reuse, as it's more about reuse. I don't think it would be very interesting to have a by-country section as the situation in almost all developing countries is quite similar: pretty much no sewage treament; sewage collection only in the CBDs of major cities. EvM-Susana (talk) 22:26, 26 December 2014 (UTC)

Proposed name change to "wastewater treatment"
I propose to change the name of this article to "wastewater treatment". The term sewage is more and more being replaced with "wastewater". Already in the lead paragraph we speak of wastewater. Sewage used to be just for household wastewwater but in municipal sewer systems there is always a mixure of households, some wastewater from industries or commercial activities as well as stormwater. "Wastewater treatment plant" also should redirect to here (at the moment it redirects to "water treatment" which is not helpful). The term "sewage treatment plant" is also used but in my opinion WWTP is more common worldwide. Note there is a separate article on "industrial wastewater treatment" which could nicely be linked to from the page of "wastewater treatment" when it is called wastewater treatment instead of "sewage treatment". EvM-Susana (talk) 18:45, 27 December 2014 (UTC)
 * Wastewater is a more encompassing term for a subject of sufficient interest to generate adequate text for subordinate articles. I disagree with the assertion that sewage treatment systems will always contain stormwater and industrial and commercial wastewater, although such components are common in larger municipalities. I favor retaining the present name for this article, although I suggest wastewater treatment and wastewater treatment plant might be changed from simple redirects to disambiguation pages. Thewellman (talk) 20:00, 27 December 2014 (UTC)
 * Thanks, so we agree that wastewater is a bit broader than sewage? So wastewater (treatement) could be the main article and sewage (treatment) could be one thereunder? However, there is no real difference between a wastewater treatment plant and a sewage treatment plant, except in the case of purely industrial wastewater treatment plants (and even they may use biological processes such as activated sludge) - and for that there is already a decent Wikipedia page of its own (called industrial wastewater treatment). In any case, a redirect from wastewater treatment to "water treatment" is wrong... I don't quite understand your idea for a disambiguation page? Which terms would be listed on such a page? Don't we need to have several? Would you agree to have a redirect from wastewater treatment to sewage treatment? EvM-Susana (talk) 21:36, 27 December 2014 (UTC)
 * Our disagreement may be wider than I initially recognized. Wastewater is MUCH broader than sewage. Wastewater is any water no longer needed (or suitable) for its most recent use. Wastewater includes such diverse sources as firewater, agricultural irrigation return flow, filter backwash, steam condensate, boiler blowdown, contact and non-contact cooling water, spent ion exchange brines, and washwater from papermaking, textile bleaching, food processing, and vehicle washing. Each of the wastewaters has unique treatment requirements. While some treatment requirements are similar to one or more stages of sewage treatment, they usually do not require disinfection, often do not require secondary treatment, and sometimes do not require primary sedimentation. Waste concentrations may be so different from sewage that pretreatment is required prior to discharge to a municipal sewer. The fact that many large municipalities use a single collection system routing varied wastes through their sewage treatment plants may obscure the disadvantages of combined wastewater treatment.


 * A wastewater treatment disambiguation page would look something like:


 * Wastewater treatment may refer to:
 * Industrial wastewater treatment, preparing water from an industrial use for return to the environment.
 * Sewage treatment, preparing sewage for return to the environment.


 * A wastewater treatment plant disambiguation page might be similar:


 * Wastewater treatment plant may refer to:
 * A sewage treatment plant also treating wastewater from industries or commercial facilities connected to the municipal sanitary sewer or combined sewer.
 * An Industrial wastewater treatment plant, preparing water from an industrial use for another use.
 * An API oil-water separator, for removing separate phase oil from wastewater.
 * A clarifier, for removing solids from wastewater.
 * A trickling filter, to reduce the biochemical oxygen demand of wastewater.
 * A carbon filtration plant, to remove toxic dissolved organic compounds from wastewater.


 * I concur with you that redirecting wastewater treatment to water treatment may be confusing, but I believe the original intent was to recognize treatment as making raw water suitable for some specific use, rather than implying potable water for domestic use as a layman might interpret the term. Thewellman (talk) 01:20, 28 December 2014 (UTC)


 * I agree with Thewellman and I would also add articles such as Agricultural wastewater treatment and there are probably many more. Water treatment is the top level entity below which is Wastewater treatment and with the individual articles (where appropriate) referenced from those articles  or disambiguation pages.  Velella  Velella Talk  04:54, 28 December 2014 (UTC)

OK, I see what you mean. So can you set up those two disambiguation pages? That would be good. - But "water treatment" is not the top level entry because water is not equal to wastewater. If I look for wastewter treatment, I would never look under water treatment. Water treatment primarily stands for potable water treatment. Water is not (yet) polluted and has not (yet) been through a process. - Having those proposed disambiguation pages would solve our problem, I agree with Thewellman. EvM-Susana (talk) 10:20, 28 December 2014 (UTC)


 * Done. Thewellman (talk) 16:15, 28 December 2014 (UTC)
 * It's still a WP:DABCONCEPT. The concept is the treatment of wastewater. bd2412  T 04:31, 30 January 2015 (UTC)

Less information on sludge treatment on this page?
I think we should trim down the information on sludge treatment on this page and rather move it to the existing page on sewage sludge treatment. For example, the recent addition about the Omni processor should in my opinion rather be on the sewage sludge treatment page as it is clearly a process for sewage sludge only, not for sewage treatment: New research developments[edit source | editbeta] ''A new sewage sludge treatment process aimed at developing countries is currently under development. It is called the Omni Processor and is a self sustaining process which uses the solids of the sewage sludge as fuel to convert the waste water into drinking water and surplus electrical energy.[27]'' EvM-Susana (talk) 11:43, 13 January 2015 (UTC)
 * To reduce this article to a manageable size, I support moving much of the description of alternative sludge treatment and disposal options to a subsidiary page; while leaving a summary and main article link on this page. Thewellman (talk) 16:40, 13 January 2015 (UTC)
 * Yes, let's do it. This will also help to improve the article on sewage sludge treatment which so far has almost no references. I would say ALL information about sewage sludge treatment should be moved to the existing sewage sludge treatment page (i.e. not just the information on alternative sludge treatment), except for a short summary that can remain on the page of sewage treatment. EvM-Susana (talk) 19:41, 13 January 2015 (UTC)
 * Done thanks to Thewellman. EvM-Susana (talk) 10:39, 14 January 2015 (UTC)

Gold in poo
Perhaps imbibing Goldschläger has something to do with this. 7&amp;6=thirteen (☎) 15:23, 4 May 2015 (UTC)

External links modified
Hello fellow Wikipedians,

I have just modified 5 external links on Sewage treatment. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
 * Corrected formatting/usage for http://www.environment-agency.gov.uk/business/444304/1290036/1290100/1290353/1294402/1311542/?version=1&lang=_e
 * Corrected formatting/usage for http://toxics.usgs.gov/highlights/wastewater_fish.html
 * Added archive https://web.archive.org/web/20130610102220/http://www.pub.gov.sg/about/historyfuture/pages/newater.aspx to http://www.pub.gov.sg/about/historyfuture/Pages/NEWater.aspx
 * Added archive https://web.archive.org/web/20131224102422/http://www.johnrashton.securemachines.co.uk/documentbank/the%20healthy%20city%20and%20the%20ecological%20idea.pdf to http://www.johnrashton.securemachines.co.uk/documentbank/the%20healthy%20city%20and%20the%20ecological%20idea.pdf
 * Added archive https://web.archive.org/web/20060904172532/http://ironwood.cpe.uchicago.edu/CPE_Workshop/paper/Cain-Rotella-Sept2005.pdf to http://ironwood.cpe.uchicago.edu/CPE_Workshop/paper/Cain-Rotella-Sept2005.pdf

When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.

Cheers.— InternetArchiveBot  (Report bug) 18:56, 14 September 2017 (UTC)

Propose Merging with Wastewater Treatment
I propose that wastewater treatment be merged into sewage treatment. The subject is exactly the same in common usage of the terms, and the information is mostly duplicates that could be consolidated better on this page
 * Please see the above discussion: Proposed name change to "wastewater treatment" Although other wastewaters are commonly treated with sewage for reasons including dilution and economy of scale, merger would obscure both the significantly different treatment requirements for differing wastewaters and the reduced fraction of pollutants removed from combined wastewaters. Thewellman (talk) 00:57, 2 January 2018 (UTC)


 * Oppose merger as per Thewellman . Please also see a variety or articles on waste water treatment including Industrial wastewater treatment, Agricultural wastewater treatment etc. all of which would somehow have to be shoe-horned into one article. There is some significant overlap but that would be best dealt with by pruning Wastewater treatment. There seems to be no benefit to this proposal. (apologies, I now realise that I said the almost identical thing in 2014)  Velella  Velella Talk  07:01, 2 January 2018 (UTC)


 * Also Oppose from me but we need to take another look at how we can make it clearer that it's not the same. I think the two articles for treatment are fairly OK, but last time I checked I found quite a bit of overlap between wastewater and sewage, e.g. in the lead. This needs to be worked on.EMsmile (talk) 00:55, 18 January 2018 (UTC)


 * This issue still requires looking at. I just realised that when it comes to the global situation, the term used in most publications by the UN is "wastewater treatment" but we would call it "sewage treatment" within the Wikipedia context. As a result, there is now a bit of new content on the wastewater treatment article about the global situation which should probably be moved to "sewage treatment". But other editors will probably continue to add content to "wastewater treatment" in future because colloquially it is used perhaps even more than "sewage treatment" nowadays. I also have the feeling that the term "wastewater treatment plant" (WWTP) is replacing "sewage treatment plant" (STP) in many cases. So we have a problem here that is not going away... EMsmile (talk) 02:39, 29 March 2021 (UTC)
 * I have made some modifications to both articles in the meantime and hope that the borders between the two articles are now clearer. We just have to make sure that in future, new editors don't add content to wastewater treatment that already exists at sewage treatment. Hopefully, the wastewater treatment article will remain as a more high-level overview article that does not go in depth in anything. EMsmile (talk) 04:44, 25 August 2021 (UTC)

Parochial?
Some of the article seems to have been written as if it's only about the U.S. &mdash; e.g., "Sewage collection and treatment is typically subject to local, state and federal regulations and standards." --84.93.89.54 (talk) 12:23, 30 January 2019 (UTC)
 * I agree this is a broader issue for many Wikipedia articles. If you see anything that requires changing, please do point it out or make the change directly if you can. EMsmile (talk) 02:41, 29 March 2021 (UTC)

Possible promotion of this article to GA ststus
There is a discussion here proposing that it might be appropriate to promote this article to GA status. Because this may impact other articles, the discussion is currently at the Sanitation Project talk page where comments and suggestions are welcome.  Velella  Velella Talk 15:05, 29 March 2021 (UTC)

Restructuring work (Aug 2021)
I have just made quite some changes to the article. What I tried to do is this:
 * 1) Provided a better balance between different types of sewage treatment processes. The current emphasis was too much on the activated sludge process.
 * 2) Provided information about some of the low cost treatment methods.
 * 3) Provided information about how to select the right treatment process for a given case.
 * 4) Reduced some content that was repetitive or too detailed if sub-articles existed.
 * 5) Moved the history content to history of water supply and sanitation and replaced it with an excerpt. This is to keep all the history stuff in one place rather than having overlapping content in several places. Hopefully like this it will be enough to give people an idea and to show them where they have to look for more information.
 * 6) Tried to reduce some of the focus on the US by providing more information about developing countries, using the book by Marcos Von Sperling which is available for free as a pdf file which makes it very handy. EMsmile (talk) 04:48, 25 August 2021 (UTC)

"Crap plant" listed at Redirects for discussion
A discussion is taking place to address the redirect Crap plant. The discussion will occur at Redirects for discussion/Log/2021 August 25 until a consensus is reached, and readers of this page are welcome to contribute to the discussion. firefly ( t · c ) 08:13, 25 August 2021 (UTC)

Reviewer's comments
I am working with an external content expert (Marcos Von Sperling) to review this article. This is part of this project. I will save after each small change and explain in the edit summary what was done. Happy to engage in further discussions on those changes. He has also sent me some images, some of which I will also include. EMsmile (talk) 06:20, 6 October 2021 (UTC)
 * I have now added all the reviewers comments to the article. EMsmile (talk) 03:35, 14 October 2021 (UTC)

Use of images in the article and in the lead
I have just added more images that were supplied to Wikimedia Commons by Marcos Von Sperling. The aim here is to show the variety of sewage treatment process and sizes that exist around the world, i.e. not to just focus on the activated sludge process. For the same reason, I have also created an image collage for the lead now. We can discuss further if I found a good balance or if we need different photos that are more suitable/appealing. EMsmile (talk) 03:35, 14 October 2021 (UTC)

What to do about long sentences with enumerations
Hi page watchers: I came back to this article today to make some corrections to content that I had added a year and a half ago to ensure it's not violating copyright (I found out that the very good book by von Sperling is open access but has an ND NC licence which was not clear from the website; so not compatibly licenced). Anyway, while doing this work I came to a point where I was undecided what to do about two long sentences that enumerate certain factors. I put them in quotes for now but I guess this is not elegant. However, I also think it makes little sense to now find synonyms for each term; and I can't really change the "sentence structure" to paraphrase it as it's just a listing of factors. I could drop some factors from the list but I'd find that almost like WP:OR, i.e. me deciding which one is more important than another one. Also the whole point is to show that there are numerous factors to consider. (I do know that Wikipedia is WP:NOTTEXTBOOK) I am curious to see how others with an interest in this topic think that this should be handled. Also pinging User:Femke and User:ASRASR and User:Velella.

This is the text block and in bold the two sentences (I guess the number of times that the word "requirement" appears could be reduced): This is because the main important factors to be considered when evaluating and selecting sewage treatment processes are numerous. A textbook listed them as follows: "process applicability, applicable flow, acceptable flow variation, influent characteristics, inhibiting or refractory compounds, climatic aspects, process kinetics and reactor hydraulics, performance, treatment residuals, sludge processing, environmental constraints, chemical product requirements, energy requirements, requirements of other resources, personnel requirements, operating and maintenance requirements, ancillary processes, reliability, complexity, compatibility, area availability".

With regards to environmental impacts of sewage treatment plants the following aspects are included in the selection process: "Odors, vector attraction, sludge transportation, sanitary risks, air contamination, soil and subsoil contamination, surface water pollution or groundwater contamination, devaluation of nearby areas, inconvenience to the nearby population". EMsmile (talk) 18:31, 8 March 2023 (UTC)


 * I think a quote like that should be avoided for a couple of reasons:
 * You're misrepresenting the source. The source does not use this quote, but has a table.
 * the length of the first quote is individually nearing the place where copyright comes into play (for most articles, I'm concerned about your total quoting not the individual quoting)
 * the sentence is way too long. Using sentences like this is exclusionary, as it makes Wikipedia inaccessible for people with low-to-average reading skill.
 * The sentence as too difficult (WP:MTAU); without context you make this more difficult than the original academic source. I had no idea what influent characteristics were till I read the context in the academic source...
 * If you need to whittle down on a lot of factors, you can use multiple sources and see what other sources say is important. In general, listing loads of factors gives little insight to our readers, as you're omitting any context. —Femke 🐦 (talk) 19:00, 8 March 2023 (UTC)

EMsmile (talk) 18:31, 8 March 2023 (UTC)


 * For the lay reader and even the moderately well informed reader, these comma separated lists are quite intimidating. Within them the individual terms are also highly specialised and probably need to be individually explained, at least in some cases. I think that I might be inclined to to start with a broad, probably tier four, headings setting out the broad topics which might be "Inputs", "Processes", and "Outputs" and within these describe the components in simpler English while still quoting the accepted technical term. This probably means re-using the same ref or refs several times, but that isn't a problem. The text already says it is technical and complicated, so chopping the explanation up into easier to digest paragraphs should aid comprehension. I would suggest that the section is looked at again. The starting sentence includes ...decision makers need to take into account technical and economical criteria which is getting close to an instruction and grazes uncomfortably close to WP:NOTMANUAL. Perhaps better to say Many technical, environmental and economic factors affect the design of a sewage treatment plant and, with the exception of small rural works, each one will be designed to suit the particular conditions encountered.. Then the 4th tier headings could follow with a common English explanation of the terms where they are less obvious and a rationale for their inclusion in the assessment and design. Happy to help and advise as any change goes along, but my ability to contribute much is inhibited by real life at present.  Velella  Velella Talk  22:46, 8 March 2023 (UTC)
 * Sounds good, please go ahead. I don't have much time at the moment for the topics around wastewater (my main focus currently is climate change). I just came back to this article in order to ensure there is no copyright violation that I could have introduced when using that book by von Sperling... I wonder if your suggestion would make it too detailed though, with level 4 headings? Please feel free to remove anything that doesn't conform with WP:NOTMANUAL. I also have to re-look at sewage, again because of the von Sperling book... EMsmile (talk) 10:53, 9 March 2023 (UTC)
 * Ah good news: the publisher just sent me an e-mail to say that this volume (volume 1) is in fact CC BY. He wrote: "It has been agreed with Marcos von Sperling that the licence for volumes 1-6 will be CC BY. Vol 7 is CCBY NC ND. This information will be added to the homepages of the book." I will add the info also to the ref list. At least this means there is no copyright violation with the content I added here and also at sewage. And I can take out those quotation marks. EMsmile (talk) 16:27, 9 March 2023 (UTC)


 * I have been sketching out a less technical explanation, without any additional headings, as a replacement for the above section of text. My current draft is here . Comments and suggestions should be made in this thread rather than at my sandbox talk page. I am aware that several more sources will also be needed. Thanks  Velella  Velella Talk 23:31, 10 March 2023 (UTC)