Updated 7/11/19 - A **process change to improve production quality
There are six separate solids recovery streams which need to be dealt with.
- Shadehouse Swirl and Bio-Filtration solids
- Pump Area Swirl and Bio-Filtration solids
- Pump Area Sand Filtration backwash solids
- Lower Pond Bio-Filtration solids
- Activated sludge solids
- Lower Pond to Shadehouse Flooded Pipe
The system which allows me to filter out the solids and recover the solids filtrate consists of 6x200L polythene drums which are linked by 25mm drum connectors to allow first settling then filtration and finally automated pumping to retreat the filtrate by treatment in the Activated Sludge System.
The above system can turn the below left sample to become the below right sample in a just a few hours.
Each ‘batch’ consists of around 400-500L of sludge/water liquor which is held to settle out for up to 12 hours depending on its settleability.
In most cases 95% of solids have settled in 3-4 hours but I usually allow around 6-8 hours for up to 98% to settle.
At that time the settled liquor (in the Settling Tanks) is allowed to run into the the Settled Tanks where a fine stainless steel mesh filter covered in white polythene filter material filters out most of the remaining sludge particles as it passes into the Solids Filtrate Tank.
The clear liquor (or Solids Filtrate) is then pumped from the Solids Filtrate Tank to my Storm Water Sump in a controlled manner whereby pumping stops at high level in the storm water sump.
This then is forwarded to the Grey Water Sump as the Treatment System is able to handle intake.
It usually takes around 3-4 hours for the 400-500L of Solids Filtrate to be run into the Treatment System depending on any other solids system inflows at the time.
The below Grafana trend shows the past 24hrs tank levels. Overnight the system was empty but receiving minor inflows. At around 0730 this morning I backwashed the sand filter to fill the Settling Tank (green trendline). As the Settling Tank filled to overflow into the Settled Tank (orange trendline) you can see at 0810 the rise in level of that tank and the subsequent rises as my solids removal system sends the waste stream to the settling tanks. The sudden drop later in the day is when the Settled Tank is released to the Solids Filtrate Tank.
Every day (and just prior to backwashing the sand filter) the bulk settled sludge is removed from one of the three Settling Tanks to further separate the water from the settled sludge. This is a very simple, fully manual, three step process done when the Solids Removal System is ‘empty’ after the previous days settling is completed.
- I first ensure the Sludge Concentrating Tank is empty and the drain valve is closed.
- Then I pump the 50 odd litres left in the desired Settling Tank (the one due for cleaning) to the Sludge Concentrating Tank.
- A backwash is then completed which refills all three Settling Tanks.
After 24 hours the settled liquor in the Sludge Concentrating Tank is then allowed to run freely (by gravity) to the stormwater tank. The remaining thickened sludge is removed by using a wet/dry vac after the sludge has filled the “sludge concentrating area” around every 7th day or so.
If not done after the 9th or 10th day, sludge will be over the level of the drain allowing sludge to re-enter the input system.
If done around the 7th day the remaining concentrated settled sludge consists of around 40L quantity with a good layer of clear liquor on top. This high nutrient waste is then sent to my compost bins for future use onsite.