Upgrading Slums to Basic Decent Housing
You can't keep the rich and privileged healthy while not doing the same for their servants. That was a big problem in India during COVID because a lot of domestic servants live in slums and the slums were at high risk of spreading COVID.
The difference between slums and basic decent housing is you can actually stay healthy in the latter and reasonably dream of and work towards a better future for yourself or at least your children. There's adequate hygiene and support for the ability to feed yourself properly even if there's a lack of electricity and/or lack of running water.
If you have NO development, like in a refugee camp, you can potentially design small homes with water catchment systems and nearby tree urinals and latrines. This may be relatively straight forward, sort of a low budget, off-grid suburb.
The modern suburb was born in the 1950s because it was a means for solving the housing shortage in part because greenfield development is relatively easy to design and build.
(I do not believe suburban development is inherently racist. They used redlining and other social practices to exclude people of color and would have excluded them if the solution they used had been downtown skyscrapers.)
But if you already have slums housing substantial numbers of people, you probably need to come up with different sets of plans that respect the existing infrastructure and add stuff to it, which is a bit trickier.
Upgrading existing slums to basic decent housing means adding adequate water infrastructure and bits that support adequate nutrition in spite of probably having no pipes and/or no electricity while working with and working around existing buildings.
You would need to survey the slums and think about how and where to ADD tree urinals, latrines and water catchment systems. And how to make minimum viable kitchens as well, which require access to clean water but also need food storage and at least one means to heat food.
My hypothetical solution for local treatment of collected rain water is peroxide and copper plus filtration. r/Gaza2050 has a post where I talk about that with enough detail that someone should be able to fact check my assumptions and design something based on the constraints I describe.
If you can find existing plans with water catchment for an off-grid home, examining that may help you come up with plans for this more challenging process of adding water catchment to an existing structure in an existing densely populated slum.
I would probably start with tree urinals inside the slums, then figure out how to add latrines and constructed wetlands as waste water treatment nearby and also start experimenting with water catchment and local treatment and figure out what works.
You can probably put tree urinals within the slum and latrines with a constructed wetlands beside it. People need to urinate more than poop and if you teach women to pee standing up, they only need a latrine to poop or while on their period.
If you use fruiting trees (fruit or nut trees), you can add free food to the slums. You do need to work out who gets to take the fruit. This is a better problem to have than starvation.
One potential solution if there are small yards:
You use fruiting trees in the yards and that household owns the tree urinal(s) and the fruit produced. Use non fruiting (male trees that prodice pollen) as public urinals that also pollinate your privately owned female fruiting tree urinals.
See also:
Development in very underdeveloped areas amd all posts labeled Very Basic Water Infrastructure.
There are pinned posts plus posts labeled Yurts on r/HousingWorks. That's what I recommend as a place to start if you wish to design basic decent housing without electricity or running water.
It's noted as a resource on the About page on Project SRO in case the information on that site is too urban/monied/upper class for what you are dealing with and trying to accomplish.
See also:
You don't absolutely NEED electricity or running water. You do need adequate access to clean water, toilet facilities, food storage and the ability to heat food.
Develop a food culture around shelf stable foods, ready access to FRESH foods and whatever cooking method WORKS for these people that ideally many already use and have the means already.
ASK people in the slums how they cook at home. Find an existing method that is already in use and incorporate it into your designs.
It's fine to have options, like THIS method OR that one. If you find two or three common methods, make plans whixh keep all of them in mind.
Food Basics and stuff it links to and other things I've referenced throughout this post talk about how historically UPPER CLASS Americans used shelf stable foods, well water, and FRESH foods before we had running water, electricity and a cold storage supply chain.
The basin and pitcher mentioned on Very Basic Water Infrastructure was the norm in upper class American homes at one time and it's the reason a plumbed sink that looks like a basin sitting on a countertop is an upper class style. It hearkens back to an era where upper class homes had a wash basin and pitcher and servants emptied and cleaned the basin and refilled the pitcher daily.
Financing:
Water.org may be willing to provide loans for the water infrastructure parts.
People with servants may be happy to donate money to this to get their servants healthier.
In fact, IF it works to add tree urinals to small yards and kitchen upgrades to individual slum homes and water catchment, you may be able to get the ball rolling by asking people to cover the cost for this for the home of their servant.
Then they are paying for something that directly and immediately improves their own lives instead of some nebulous hand wavy "be generally nice to a lot of poor people you don't know and HOPE it eventually benefits you."
Last:
If you have adequate clean water, you can clean up at a sink, but when I was homeless, it made a huge difference to be able to get a proper bath or shower at least once a month in addition to cleaning up at the sink in public bathrooms.
Consider adding public showers, possibly on a fee basis, near the latrines. I was able to pay $1 and get a proper shower (cold water only) at a beach bathhouse in Port Aransas or a monthly fee and get access to hot showers with more amenities at a campground.
I've written about middle class style showers for homeless Americans in multiple posts on this site. You may wish to find those posts and read them. (There is a Showers label. I don't know if it's comprehensive.)