Can we develop a wastewater treatment system without any machinery "even simple one"? Note: "No power available to run a normal treatment plant"

Sure on-site wastewater treatment for small communities can work naturally without any need of power and I have developed and designed one in Egypt you can have a look on my web site

www.anwarmanaf.webs.com 

For my personal opinion I think NO,

1.How you pump your Influent

2.How you provide or inject air in the aerator tank.

3.How to make sludge into the belt press without pumping into it.

4.How to run your sedimentation tank?

5.You need a large power to drive big motors for influent up to effluent.

yes. using coagulation process by using alum of required quantity

Yes a simple wastewater treatment process can be operated without power source by sedimentation, however the sludge will be removed manually.

There are environmental  systems used to treat waste water in use today all over the world. You can direct waste water to open pools that have reed and the bacteria work on it.

The slow process would give eventually clean water to the nature without any machinery.  

YES,

We can using multi layer of filters sand- cotton, stone , sand ...

the only way could be settling process and it will remove only particulates.

Waste water can handling without machinery with air contacted by cascade treatment, that is can reacted with Oxygen.

Wastewater can be simply treated by using the method of sedimentation 

Yes ,we can depending on the evaporating and condensing the liquids ,then the sludges will be remain.or by using a filteration system with tanks has screens on its outlet or by using sedmintation tanks.

According to the unit which is not performing properly.

If the problem id the biological treatment, we can simply enhance it by adding some MBBR media to increase the aeration surface area and allow the aerobic bacteria to live and grow in better conditions, it will decrease the produced BOD and doesn't need any extra power.

If the problem is tertiary treatment, We can study whether coagulation or flocculation will solve the issue or we need more settling area so we can replace the traditional clarifier with Lamella type.

it will all depend on where is the problem exactly.