An Overview of Solids Handling

The purpose of wastewater treatment plants is to remove impurities and produce water that can safely return to the water supply. In manufacturing plants, this process involves treating water to remove harmful chemicals. The wastewater plant must remove any solid matter flushed into the system for a municipal water supply. Solids handling is the process that takes these materials and generates a safe solid that is ready for disposal.

From the Water Stream to Wastewater Solids

Different types of solid matter can get into the wastewater stream. If stormwater runoff drains into the system, it can bring wrappers, bags, and other plastics. These contaminants are in addition to what people manage to flush into the sewer.

Filtration is one of the first steps in wastewater solids processing. The treatment removes solid contaminants that will not break down in the upcoming digestion process. 

An additional preparatory step involves equipment like a grinder or macerator. These devices process biodegradable materials like hair and flushable wipes. Breaking these contaminants into smaller pieces makes them easier to process into biosolids.

Sludge Generation

After the initial filtering and processing, the treatment plant wants to separate solid matter from the water. Most wastewater plants use settling tanks for this purpose. Wastewater flows slowly through the tank, and the force of gravity pulls solids out of suspension. The layer of solids at the bottom of the tank is known as sludge. Processing this sludge for disposal is the essence of solids handling.

After the settling tank, the sludge still contains a great deal of water and has the consistency of the thick slurry. This substance has an unpleasant odor and carries harmful bacteria. Some parts of the world dispose of sludge in this state. However, for public health reasons, most countries now demand that it go through further solids processing.

The Problem of Water Removal

The goal of solids handling technologies is to deliver a product that is dry, sterile, and has minimal odor. Removing water is usually the first step in this process, but it can be problematic.

Sludge drying beds that use the evaporating power of the sun are one of the oldest methods. However, they’re time-consuming and impractical in areas with a high output volume.

Other water removal techniques include centrifugation and in-house evaporation. While these are effective means of removing liquid, they can be energy-intensive. However, some solids handling technologies produce energy as part of the process, lowering the cost of this step.

Destroying Microorganisms in the Digestion Phase

Untreated sludge is a dangerous substance with harmful bacteria. Before a plant can dispose of sludge as biosolids, it must treat the material to remove this hazard. This process is known as digestion and takes two primary forms: aerobic and anaerobic.

Aerobic digestion involves the presence of oxygen. During this process, bacteria use oxygen to break down organic material. The aerobic model is the faster of the two techniques, but it releases carbon dioxide, a concern in climate change awareness.

Anaerobic digestion uses heated tanks to encourage fermentation. This process releases methane which plants can harvest and reuse to power operations. However, the equipment for an anaerobic digestion process is expensive, and it takes several days to complete.

New processing techniques are on the horizon. For example, researchers at the Paul Scherrer Institute in Switzerland develop a catalytic process that uses ruthenium to convert organic matter to biogas. In initial testing, this technique performed a sludge breakdown in a few minutes instead of the multiple days needed for traditional anaerobic digestion.

Monitoring the Treatment of Wastewater and Wastewater Solids

High Tide Technologies specializes in SCADA systems for municipal water treatment, collection, and distribution systems. Water utilities can track critical information throughout the system by employing cloud-based data acquisition equipment. Managers can see real-time performance data like water pressure, flow rates, and temperature. The result is a more efficient and predictable system. Contact us today to learn more about how SCADA can improve your facility.