AMMONIA AND PHOSPHORUS REMOVAL IN WASTE WATER TREATMENT

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Juniper Lang
6 years ago
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1 AMMONIA AND PHOSPHORUS REMOVAL IN WASTE WATER TREATMENT PROPERSITION PAPER FOR REVIEW:- The British Water small packaged treatment plant group are seeing consents to discharge imposed by the legislative bodies in the UK that are unachievable by an average packaged sewage treatment plant, irrespective of testing to EN The two main issues are with respect to ammonia (NH4-N) and phosphorus removal. For ammonia removal sufficient alkalinity is required for Nitrification (NH4-N removal) the levels required to achieve better than 10mg/l NH4-N would not be generally found in raw water supplies in Scotland, Wales and large parts of England. With regards P removal at this size it is unreasonable to expect a standard plant to achieve Bio-P removal leaving the practical option of chemical dosing of Iron or aluminium based coagulants to achieve treatment. 1. Ammonia Removal to levels sub 15mg/l NH4-N based on an influent with levels of 40mg/l (typical sewage) you would require 257mg/l of alkalinity to remove 25mg/l NH4- N plus a residual of 80mg/l to maintain ph at reasonable levels. Attached FIG 1 & 2. No allowance for additional alkalinity should be considered as it passes through the dwelling, if a water softener is used then the alkalinity will reduce slightly. Insufficient alkalinity will inhibit biological nitrification so dosing on a domestic level is the most reasonable option. Recirculation of liquors in a treatment plant may be able to recover some alkalinity through the de-nitrification (NO3 removal) process. Technologies available to resolve the issue are generally related to dosing with one of the following:- Calcium oxide (lime based product) Sodium carbonate (Soda ash) Magnesium hydroxide (Caustic potash) Sodium hydroxide (Caustic) 2. Phosphorus Removal to sub 2mg/l. A significant amount of work regarding P removal is being undertaken by the Utilities with the additional support Cranfield University, Bristol University and Portsmouth University. In all instances chemical dosing with some form of solids removal is being seen as the way forward for sub 3mg/l P in the final effluent. Some adsorbent technologies exist and are used at a domestic level in some of the Scandinavian countries with a varying degree of success. Further works by the packaged treatment group to identify these technologies should be undertaken Domestic package treatment plants with chemical dosing have successfully achieved under 0.5mg/l P with aluminium dosing. As an integral part of the treatment plant, this

2 product will be certified to E , rather than EN for standalone tertiary treatment products OPTIONS For effective phosphorus removal the following can be used: - Ferric Sulphate Ferrous Chloride Alum Poly Aluminium Chloride (PAC) In cases where both ammonia and phosphorus reduction is required, additional alkalinity dosing may be required to replace that lost by the acidic chemicals required for the phosphorus reduction. 1. Continue to impose strict consents and accept EN test results even though most test house ensure sufficient alkalinity. ph, as measured at the Notified Body PIA in Aachen, Germany is 7.1, generally an indication of sufficient CaCO3. Undertake no field performance testing to ensure compliance but reliance on public intervention to highlight discharge failures. Ammonia and P failures will only be seen as eutrophication of the receiving body of water not at point of discharge. 2. Allow chemical dosing when imposing a strict consent on either a domestic or commercial discharge, a route the E.A. have already expressed concerns over reliance on the householder to maintain the chemical dosing beyond the first fill. 3. Is there scope for the treatment plant service contract to include responsibility for provision and adjustment of the chemical dose, in order for the EA to be comfortable with the likelihood of the treatment plant meeting the consent in the future? There may be objections raised due to the limited manpower in the EA to monitor such systems! 4. Consent only when a recognized and tested method of treatment is available to remove NH4-N and P, this will increase the discharger s costs significantly. 5. Advise households to use Phosphorus free detergents with no consent on ammonia being imposed, then rely on imposing stricter consents on larger non domestic facilities downstream to prevent eutrophication.

ALKALINITY ADDITION: THEORY AND BEST PRACTICE

ALKALINITY ADDITION: THEORY AND BEST PRACTICE Kuteiba Hussein (Mott MacDonald), Raj Valabh (Mott MacDonald), Simon Flanagan (Xylem Water) ABSTRACT Alkalinity is an often overlooked water quality parameter