Sinking in sludge: How to identify excessive sludge accumulation

Many wastewater lagoons eventually face a common challenge—excessive sludge accumulation. This buildup can significantly impact the treatment process, causing several operational issues such as odours and elevated levels of BOD, TSS, and ammonia in the effluent. Here are the most common signs of excessive sludge accumulation and a simple approach to maintain optimal system efficiency and effluent quality.

Visible signs and odour

In some cases, sludge is visually apparent, with sludge islands floating on the lagoon’s surface or mounds rising above the water level. This exposed sludge can release methane or hydrogen sulfide gas, resulting in foul odours and complaints from nearby residents. Observing such phenomena means sludge should be addressed promptly.

Turbidity and effluent quality

Monitoring the lagoon through regular influent and effluent sampling is crucial for detecting sludge-related problems. High turbidity, poor nutrient removal, and changes in colour often indicate sludge accumulation. Sludge particles may also contaminate the effluent, reducing its clarity and leading to abnormally high or non-compliant total suspended solids (TSS) measurements.

Storage capacity, nutrient removal, and algae blooms

As sludge accumulation increases, a lagoon’s storage capacity and retention time decreases. This can impede the lagoon’s ability to effectively remove nutrients, which can cause problems such as algae blooms or exceedances in regulated discharge limits.

Short-circuiting and washout

Excessive sludge accumulation can create channels within the lagoon, causing wastewater to bypass the intended treatment process. This flow short-circuiting results in reduced retention time and compromises treatment performance. If a lagoon also experiences high hydraulic loading, such as a storm event, the high flow and short retention time can cause washout of a significant portion of the microbial population. It can take days, weeks or longer for the biological process to recover, significantly impacting lagoon performance.

Benthal feedback in non-aerated lagoons

Non-aerated lagoons can experience a phenomenon known as benthal feedback, particularly during the spring season. As the water warms, turbulence stirs up the sludge blanket, releasing accumulated hydrogen sulfide and nutrients. In severe cases, the concentrations of certain wastewater constituents can become higher in the effluent than in the influent, indicating a significant sludge-related issue.

Operator access and maintenance challenges

Excessive sludge can hinder operator access to critical components that require regular maintenance. Aeration systems, inlet structures, force mains, and other essential equipment may become blocked or inaccessible due to sludge accumulation. This obstruction can compromise routine maintenance and hinder the efficient operation of the lagoon.

Fast, affordable remediation options

Regular maintenance, including timely sludge removal, is key to ensuring the long-term effectiveness of lagoon systems. Bishop Water provides comprehensive services to remove and dewater sludge from wastewater treatment lagoons of all sizes.