As sewage is moved to treatment centres via pumped systems there is a risk of waste ...

Septicity in pumping mains


Hi Nilam. If you have water treatment works using iron based coagulants then these can be used to help overcome septicity. Typically the coagulants will be taken from DAF plants and considered a waste sludge to be disposed of. They still have good sequestering potential and can help keep H2S problems down. In fact there are probably many situations where WTW discharge to sewer and companies are unaware of this beneficial effect. You could take the ferric coagulant and discharge it to the network at suitable positions. Worth a try and although it might not eliminate the problem it might help and also find a sustainable beneficial use for the coagulant. 



Nick Walmsley
Adding chemicals is always a means of last resort as it is usually the most expensive, let alone bringing all sorts of other issues e.g HSE. Much septicity is due to poor design and/or operation. The sewers should be designed for 2 fluids, sewage and air with correct velocities and management techniques for both. Many of todays sewers are based simply on minimal sewage velocity and passing bulk fluid from A to B without considering the biochemical processes in between. In fact I would strongly suggest that many designers and operators don't know the difference. Unfortunately there is no simple public text that I am aware of that sets out the design details and it is not extensively taught in tertiary institutions. Some key parameters to consider are:
- consider the system in a dynamic state not as a static peak fl;ow model
- minimise retention in rising mains
- use proportional flow control at pump stations to minimise pressure surges
- check Froude numbers to see where hydraulic changes will impede airflow
- minimise turbulence, particularly at the discharge end of rising mains
- program regular increases in rising main velocities to minimise slime build up (slime shear velocity)
- ensure you control the airflow amount and direction using pressure as well as velocity controls
- minimise inflitration of saline water (seawater = approx 7% sulphate
- educate both asset management and operational staff so they both work to the same plan
good luck
Santhanam Ramasubramanyam
Swami Valmiki Sreenivasa Ayyangarya has developed a new technology based in ancient Vedic Sciences of India which enables treatment of sewage effectively without toxicity of chemicals.The sewage is treated in a tank or pond where the solids settle as inactive sludge and grey water without odour is taken out for reuse or can be treated further, even upto drinking water quality if needed. This also has been developed by Swami Valmiki again using Vedic Sciences. Neither the inactive sludge or the grey water breed pathogens and hence there is no danger of septicity. Already demonstrated in a large temple water tank of about 500,000 litrees capacity which also breeds fish very well.Algal blooms are controlled either by additional treatment or skimmed off physically and applied to gardens and agricultural lands as mulch. The inactive sludge is still at the bottom but has posed no problem of septicity. If required, that can be pumped out and dewaterwd with belt filters.This inactive sludge is also a good soil additive to improve water retention helping reduce irrigation needs and its breakdown is need based for growth of plants due to soil biological activity, in a healthy soil, not damaged by chemical farming.
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