New general advice should be developed on phosphorus requirements

The guidance is an ambitious attempt to control the very diverse exercise of authority currently exercised by the country’s 290 municipalities in the assessment of small sewers

No analysis on the substance of the issue

The guidance lacks any discussion on the substance of the issue.
-What are the risks and impacts of small sewers?
-What are the protection needs in different parts of the country?
-How should small sewers be developed to best meet the ambitions of the Environmental Code (maximum environmental benefit at not unreasonable cost).

It is on the basis of such an analysis that requirements for facilities should be set.

Biological treatment more important than chemical

The guidance risks further cementing the general advice’s focus on recipient and phosphorus rather than opening up for greater emphasis on infection control and resource management.

It should be much clearer that the focus should be on biological treatment and groundwater protection (drinking water wells). Requirements for specific P treatment are as described below,

not justified for most of Sweden (receiving waters are depleted of nutrients or soil retention is protective). Land-based treatment provides better and safer removal of

infectious agents, pharmaceuticals and other organic substances that can negatively affect the aquatic environment than, for example, mini-treatment plants.

High protection requirements are thus directly counterproductive for water protection in most water bodies in Sweden.

The references made to court cases risk further cementing the outcome of previous erroneous judgments.

The contribution of phosphorus from individual sewage systems is of marginal importance for the discharge of phosphorus from land to sea. A similar picture applies to the contribution of different sources of phosphorus to inland water bodies. Large-scale regional changes in metabolism in our forests and agricultural areas, as well as internal metabolism in lakes, normally overshadow nutrient discharges from individual sewers.

The link between a high level of protection and the water authorities’ classification of ecological status regarding eutrophication is thus irrelevant.

Small drains simply do not affect larger water bodies.

However, high phosphorus requirements can be justified in sensitive environments, typically small spring lakes and secluded bays in cliffs and coastal areas with thin soil cover and many households with individual water supply. Even mountain waters can be sensitive in some cases. These protection needs are often combined with the need for protection against the spread of infection.

With the support of research and reports compiled by HaV itself, WRS concludes that small sewers generally have little impact on the nutrient status of our lakes and rivers. Inland waters often suffer from increasing malnutrition, which has long been known. Recently published research shows that virtually all large lakes in Sweden are undergoing oligotrophication,

✔ Oligotrophic is a water with low
nutrient levels. Oligotrophication is ongoing
nutrient depletion.

In nutrient-poor water bodies, no specific phosphorus removal is needed. However, there is often a need for effective biological treatment. Thus, in large parts of Sweden, soil-based treatment is a very suitable technology. Even very old soil beds/infiltration can provide good protection in these areas, compare the state of soil-based treatment report.

The reasons for the reduction in nutrient levels are not known, but are believed to be due to reduced leakage from forest land in particular. In oligotrophic waters, there is no need for high phosphorus removal but good biological treatment to reduce the risk of bioaccumulation of, for example, pharmaceuticals.

When considering the impact of small drains on the nutrient status of the sea, their role is insignificant,

The problem of eutrophication and small sewers is thus greatly exaggerated. There are of course local lakes and small watercourses that are negatively affected by nutrient discharges from small sewers.