What are the methods of sludge disposal?
In this article, we’ll be discussing the different sewage sludge disposal methods and how they’re performed. Also, we’ll be looking at the general idea of sewage sludge and the cost of disposal, among other things.
You’re likely reading this article because you seek answers to the question of waste management.
Here, you’ll find all the essential answers you’re looking for. In the end, you should be better enlightened on what it takes to dispose of your sewage safely and how much cost will be incurred.
Options and Cost Of Sewage Sludge Disposal
Proper waste management is a necessary procedure vital to the environment and the normal functioning of societies. Here, multiple processes or treatment options are available for handling sewage waste.
All of these methods are geared towards the safe disposal of such.
About Sewage Sludge
Before we get to details on sewage sludge disposal methods and procedures, we have first to provide a basic overview of sewage sludge and what it’s all about.
As wastewater or sewage is conveyed through the sewer from homes, hospitals, stormwater runoff, human excreta, and industries, it’s collected in centralized wastewater treatment sites.
At wastewater treatment facilities, pollutants are removed or separated from sewage matter. Such include phosphorus and nitrogen, settled matter, oil, and grease.
After the safe removal of these harmful substances, sewage sludge remains.
Not all contaminants are eliminated from sewage sludge during treatment, as lots of these are still contained.
Examples of such contaminants are steroids, pharmaceuticals, disinfectants, endocrine-disrupting chemicals, heavy metals, triclosan, triclocarban, and antibiotics.
This raises the question of how safe the disposal procedure is and whether the process exposes humans to these contaminants. Unfortunately, most sewage sludge disposal happens on agricultural land.
They’re also applied on lawns and parks. The issue of safety is a discussion for another day.
Sewage Sludge: Any Benefits?
The disposal procedure adopted for sewage sludge largely depends on its benefits. When it comes to land utilization, sewage sludge is helpful.
These include being used for land reclamation, application of composted sewage sludge to farmlands, and application to forests.
Also, composted sludge is also used for gardening and landscaping. Here, the benefits tend to be expected for all of these disposal methods.
Various nutrients and micronutrients like phosphorus, nitrogen, potassium, copper, zinc, and iron are available in sludge and support plant growth.
What more? There are benefits such as improvement of soil quality, which leads to increased permeability to air and water and increased retention of nutrients for gravelly or sandy soils.
These perceived benefits influence the disposal methods for sewage sludge.
Sludge Disposal Methods
The discussion above has been vital to better understanding the different sewage sludge disposal methods adopted in western societies.
When it comes to the standard disposal methods, the following are easily the most popular; landfill disposal, marine disposal, and disposal in freshwater bodies (no longer practiced).
Sewage sludge is also incinerated as a way to dispose of it without much harm safely. With this said, let’s look at how each of these sewage sludge disposal techniques is implemented.
This gives you an overview of the entire process involved.
i. Landfill Disposal of Sewage Sludge
The dumping of treated sewage sludge in landfills is one of the most common disposal methods. However, there has been a steady shift in perception of the safety of dumping sewage sludge in landfills in recent times.
Such concerns are primarily due to the likelihood of wet sludge eventually leaching into groundwater.
Another concern that has affected the continued disposal of sludge in landfills is the volume of methane gas produced. There’s also an increased scarcity of landfill sites that can accommodate the volume of sewage sludge produced.
Although this is one disposal method that’s still being used in some states, it’s clear that the safety and sustainability of the process are a significant doubt.
Newer and better ways of sewage sludge disposal are being worked on to ensure increased environmental safety.
ii. Marine Disposal of Sewage Sludge
Marine disposal of sewage sludge has been a practice that has been around for quite some time.
Despite the particular toxicity levels, disposal of sludge on ocean currents serves to dilute these pollutants to make them harmless in the water.
There are increased concerns for the safety of water creatures like fish etc.
According to findings from scientific studies, it has been observed that five decades of marine disposal of sewage sludge has created around 50 square kilometers of dead seafloor in the New York Bight area.
This is a concern for environmentalists as they ponder the sustainability of the process.
iii. Disposal in Freshwater Bodies
Although this practice has been brought to a halt, sewage sludge was earlier disposed of in freshwater bodies like rivers and lakes.
Such action’s danger posed to the environment has caused a much-desired change due to this harmful practice. Today, there are legislations that prohibit such practices.
iv. Incineration of Sewage Sludge
One other way sewage sludge is being disposed of is by having it incinerated and discharged into the air. Through such action, toxicity levels are significantly reduced.
However, it raises pollution concerns for many as dispersed solids eventually settle. Based on our discussion so far, it’s evident that sewage sludge disposal poses different challenges.
Sewage Sludge Disposal Costs
The cost of sewage sludge disposal is primarily determined by the method used. A good example will be the incineration method of removal, which is capital intensive.
First, sewage sludge has to undergo an analysis to determine the presence of heavy metals before being incinerated.
Incineration incurs high energy costs and investment in extensive sewage facilities that will contain the volume of sludge being produced. The need for a skilled workforce is also paramount.
All of these considerations significantly impact sewage sludge disposal costs. In the US, sludge disposal cost per ton is around $60-$70, depending on the state.
Sewage sludge disposal methods and costs have been discussed with different techniques provided. We’ve also provided information on the composition of sewage sludge and why disposal procedures matter.