Lowering Nutrient Levels
A first step was to reduce the amount of nutrients going into the broad. The early results from research on the origin of the high level of nutrients in the broad was informative enough to persuade Anglian Water (the water authority at the time) to install phosphate reducing equipment at one of the two sewage treatment works upstream (Stalham) and to divert the effluent from the other (North Walsham) so that it did not flow through the broad.
By 1981 this work was done, and everyone hoped that the reduction in the input of nutrients would reduce the algae populations and allow water plants to re-establish. But unfortunately this didn't happen. The water stayed cloudy and phosphate levels in the water were still too high to allow the broad to recover, despite the improvements to sewage treatment works. The remaining nutrient came from the sediment, properties not connected to mains sewerage and agriculture in the river catchment, in addition to the sewage treatment works. 'Bombing' the broad to remove phosphate didn't work.
Experimental techniques for binding up the phosphate included 'bombing' the broad with Siltex, a substance which it was hoped would stick to the phosphate and take it out of the water permanently. Unfortunately, this did not work.
Further reductions in phosphorus inputs
In 1997, Anglian Water installed DynaSand at the Stalham treatment works, an additional phosphate stripping treatment system to improve removal of phosphate particles. The system involves adding ferric sulphate to sewage effluent and filtering the effluent through silos of agitated sand.
Mud pumping and biomanipulation
Clearly, one way to make a big impact (even if not a permanent one) on the phosphorus levels in the water of the broad was to get rid of the thick bed of nutrient-rich mud, lying on the bottom. In May 1992, we started to plan the huge suction dredging operation. We appointed contractors to remove 300,000 cubic metres of phosphate-rich mud (the equivalent of 160 Olympic-sized swimming pools) and work began in earnest in November 1995. A huge problem with removing silt from a broad is where to put it. The solution at Barton was a network of settlement lagoons created on 22 hectares of nearby fields.
The mud was sucked up and spread out to dry. The contractors spent a month building the settlement lagoon 'bunds' or embankments from the topsoil on the fields. The mud was pumped on to this arable land to dry out, while the water flowed back to the broad, minus its phosphorus which stuck to the solid particles of silt. The suction-dredger, or mud-pump, was connected to a pipeline, and worked its way slowly back and forth over the broad, sometimes seven days a week, for over four years.
Recycling the nutrients from the broad into crops
Once the lagoons were filled and the silt dried out, the structure and chemical content of the soil was monitored. After one of his inspections, in September 1998, Selwyn Richardson, the consultant soil scientist wrote, 'In summary I am very pleased with the root growth and development of a stable soil structure in this first year. The resulting soil should, in due course, be capable of producing large yields of a wide range of crops.' Very successful crops have since been grown.
Improvements for sailing and for fishing
Sailors are pleased with progress - they've been enjoying parts of the broad they've been unable to reach for many years, now that dredging has created deeper water around the edges of the broad. Anglers are seeing changes too - they've reported that the fishing at Barton has improved, with much better catches.
