Abstracting water at the bottom of the river close to the estuary, can pose a problem with towns upstream, discharging their sewage effluents, especially large towns. Prior to the introduction of sewage treatment works, rivers became heavily polluted causing large scale illness and death, as in the River Thames in London, and in Rome. Small towns have a limited effect, just increasing the nitrate and phosphate levels. These however are reduced by plant and algal growth, especially in summer.

When the Southend Waterworks Company applied to abstract water from the Rivers Blackwater and Chelmer in 1925, it was agreed on condition the effluents from the two main towns upstream, Chelmsford and Witham, were piped below the intakes.

Some 10 miles upstream of Langford, at Chelmsford on the River Chelmer, was the Brooke End sewage treatment works, treating water from a population of 120,000 in 2015. The combined intake of the Rivers Chelmer and Ter was sited above the weir at Rushes lock, and the Effluent discharge at up to 6 million gallons a day, below the weir to prevent abstraction with the river water. A Plan was also prepared to extend the outfall to Heybridge Basin, if the Local Authority required it to be below the Promenade Park and where most water activities took place. The river flow below rushes lock was a minimum of 200,000 gallons a dayset as the compensation amount for drought conditions and to maintain the level in the canal for the barges. In 1934 at Hoe Mill below Rushes lock, all of the fish were killed as a result of a lack of oxygen, due to the high proportion of effluent. When there was heavy rainfall and untreated water entered the river at Brooke End, Chelmsford, abstraction ceased at Langford until the contaminated water had passed. Currently an automatic system warns the controllers at Langford to untreated effluent entering the river.

The effluent from Witham was piped down to the tidal reach at Beeleigh below the intake at Langford 

Effluent Discharge at Beeleigh near Langford

In 1952 when the Hanningfield Reservoir Scheme wasintroduced, a new river Chelmer intake and pumping station were constructed at Langford to supply river water to both Hanningfield Reservoir and Langford works. This made the intake at Rushes Lock redundant, and necessitating the extension of the sewer pipeline below the new intake to join the discharge point at Beeleigh.  Provision was made with an easement (Planning Restriction) on land from Beeleigh to Heybridge Basin to extend the pipeline further down the tidal river to Heybridge Basin, in the event of the Maldon District Council wishing to reduce the pollution of the Blackwater at Hythe Quay and through the Promenade Park. This has never been implemented. The sewer pipeline from Chelmsford was duplicated in 2015 with a 1.2 metre diameter pipe. An Archeological dig was carried out in advance of the pipeline being laid. Saxon remains  were found together with cremated bones over 3000 years old, the earliest found in England, together with remains of buildings. Upstream, the river Chelmer is joined by the river Wid into which flows the effluents of Warley, Ingatestone and Shenfield, and Stebbing Brook into which flows the Stebbing effluent and that of the Sugar Beet Factory at Felstead which in the past has been responsible for an earthy taste and odour to the river.

Upsteam the River Blackwater is joined by the River Brain, and towns discharging directly into the rivers are Braintree, Dunmow, Kelvedon, Rivenhall, Coggeshall, White Notley, Bocking, and Stisted. 

Effluent Recycling

As a result of low river flows it was decided to install an effluent recycling plant at Langford. This was an interesting decision as in the past, a sewage treatment plant would not have been allowed on the same site as  water treatment.  In April 2000 Essex and Suffolk water were granted a licence by the Environment Agency to discharge recycled effluent, originally from Chelmsford Sewage Works into the River Chelmer at Scotch Marsh, Ulting  This allowed construction of the Langford  Recycling plant, with an output of 40 Megalitres a day. The processes involved reduced Phosphate, Total Nitrogen, Biochemical Oxygen Demand, Bacteria and Endocrine Disrupters. The plant was opened in 2003. The Licence also imposed certain conditions, that a monitoring program would be put in place to monitor the quality of the recycled effluent and the river receiving it, and reported to the Environment Authority annually.

The Langford Effluent Recycling Plant from 2003

Following its initial trial period it has been operational very little in recent years due to sufficient river water flow.

Langford Effluent Recycling Plant

Plan of River Chelmer, with the relevant positions shown regarding Effluent recycling

The Effluent flow from Chelmsford, down the pipeline emulates the domestic water demand, with very little smoothing. Peaks flow are seen at early morning , when people are showering, bathing, and making beverages and again early evening when meals are beibg prepared etc.  Effluent quality has also improved with less suspended  matter.